NL2034475B1

NL2034475B1 - A method and system for hashing a fingerprint minutia template

Info

Publication number: NL2034475B1
Application number: NL2034475A
Authority: NL
Inventors: David Barbour Graham
Original assignee: Csir
Priority date: 2023-03-30
Filing date: 2023-03-30
Publication date: 2024-10-04

Abstract

This invention relates to a method and system for hashing a fingerprint minutia template, for example, for online security applications, wherein the method comprises receiving the fingerprint minutia template; a user password; and determining a plurality of positionally distinct n-tuples of minutiae of fixed size from the received fingerprint minutia template. For each n-tuple, the method comprises: determining a unique class identifier (UCI) of the n- tuple, wherein the UCI is associated with one of a predetermined number of equivalence classes, based on attributes of the n-tuple, or minutiae of the n-tuple, which are rotationally and translationally invariant; combining the determined UCI, the user password, and a salt into a combined dataset; and hashing the combined dataset with a hash function to obtain a unit-digest. The method then comprises collecting the unit-digests into a hashed template.

Description

A METHOD AND SYSTEM FOR HASHING A FINGERPRINT MINUTIA TEMPLATE

FIELD OF INVENTION

THIS INVENTION relates to methods and systems for hashing fingerprint minutia templates, for example, for online security applications.

BACKGROUND OF INVENTION

Many computerised security procedures and systems require biometric data from users to be captured and verified or authenticated before being permitted to perform certain restricted actions such as accessing restricted computer/s or computer system/s including memory devices thereon such bank accounts stored on bank servers, accessing designated areas, and the like. “Biometric” data may be understood to refer to distinctive human characteristics or traits that is able to be captured electronically in a manner that they may subsequently be used to identify individual people. For example, human features which may be electronically captured to provide biometric data comprise human fingerprints, palm prints, human iris or retina, voice, facial feature/s, and the like.

Users typically enrol themselves for subsequent identification, verification, and authentication by supplying biometric data. In the case of biometric data in the form of fingerprints, users enrol themselves by providing their fingerprints which are associated therewith. Mathematical representations of the fingerprints in the form of fingerprint minutia templates are extracted from received fingerprints provided by the users and are stored in a suitable storage media for subsequent matching for identification, verification, or authentication purposes.

While only a mathematical representation of a fingerprint, if an attacker were to obtain such a fingerprint minutia template, they have effectively obtained enough information to masquerade as the owner of this fingerprint. The attacker could simply reuse the template directly, or reverse engineer the template to generate a simulated fingerprint image that would produce the same or similar template when scanned.

It has even been shown that the original fingerprint can be reverse engineered accurately from a standard fingerprint minutiae template, and techniques for reverse engineering templates will grow with time. The owner's fingerprint has effectively been stolen as a person cannot change their fingerprints.

To compound problems, it has recently been shown that biometric fingerprint matching systems, even those that return only a yes or no answer, can be queried by an attacker into revealing the fingerprints in the database.

One approach to address the aforementioned problems has been to use biometric data as inputs to a suitable secure hashing function which outputs hashes or hashed values of the input biometric data which are then stored and used in place of biometric data for purposes of one or more of identification, verification and authentication of users. For example, fingerprint minutia templates are hashed with a suitable hashing function to provide hashed templates which are stored in a suitable media and are used for one or more of identification, verification, and authentication. In this way, the risk associated with communicating and storing fingerprint minutia templates is mitigated as it is only hashed templates which are communicated and stored.

However, there are drawbacks with conventional systems which employ hashing methods in processing data in the manner described herein as they are not immune not immune to attack and often have relatively high error rates relative to the generally acceptable error rates for fingerprint matching.

The present invention disclosed herein seeks at least to address and ameliorate the drawbacks described herein and at least to provide an alternate approach to biometric matching for purposes of one or more of identification, verification, and authentication.

SUMMARY OF INVENTION

According to one aspect of the invention, there is provided a processor-implemented method of hashing a fingerprint minutia template, wherein the method comprises: receiving a fingerprint minutia template comprising a plurality of fingerprint minutia; receiving a user password,

determining a plurality of positionally distinct n-tuples of minutiae of fixed size n from the received fingerprint minutia template, wherein each n-tuple comprises at least one minutia pair; wherein for each n-tuple in the determined plurality of positionally distinct n- tuples, the method comprises: determining a unique class identifier (UCI) of the n-tuple, wherein the

UCI is associated with one of a predetermined number of equivalence classes, based on attributes of the n-tuple, or minutiae of the n-tuple, which are rotationally and translationally invariant; combining the determined UCI, the user password, and a salt into a combined dataset; and hashing the combined dataset with a hash function to obtain a unit-digest.

The method may comprise collecting the collecting the unit-digests into a hash or hashed template. The terms “hash template” and “hashed template” may be used interchangeably herein. It will be appreciated that each distinct n-tuple selected from the template may be transformed into a unit-digest. Thus, the hashed template may be a finite list of unit-digests. This hashed template may be referred to herein as a base hasher.

The “processor-implemented” methods as described herein may be analogous to “computer-implemented” methods.

The method may comprise concatenating the UCI, the salt, and the password before hashing. This may be a binary string concatenation. To this end, the method may comprise passing the UCI and/or the salt with zeros to ensure a predetermined number of bits. the predetermined number of bits to pad the UCI and the salt may be different.

In a preferred example embodiment, the n-tuple comprises two minutiae and as such the n-tuple is preferably a minutia pair or 2-tuple, reference may be made to the minutiae pair when referencing the n-tuple for brevity unless otherwise stated.

It will be appreciated that a minutia m, is an object of property properties p, o, and t, where m.p is a point called the position, m.o is an angle called the orientation, and m.t, is the type taking values amongst i: 1 where 0 is a bifurcation and 1 a ridge ending.

The set of all minutiae encountered in the “real-world” scenarios under consideration is denoted M, and called the minutiae space.

A minutiae template T is a finite list of minutiae. Fingerprints may be optionally scanned and extracted to a minutiae template. Note that in the standard ISO minutiae template standard, angles are represented in degrees, and this convention is used herein.

It will be appreciated by those skilled in the art that a pair of minutia or minutia pair or 2-tuple fit described herein is a pair of minutia <81 8 which is drawn from the same minutia template. In this regard, for a minutia pair 3%, wherein:

Jimmy A Jimi mite dip = Dof mjg, rai} sh Slo Jim, os} = Wile S{m

It will be noted that for points p and q, «if §} = arctan {fy Dg. de fel, wherein arctan2 is the 2-argument arctangent.

In this regard, d(!®) is referred to herein as the distance, and 'e:i®) and 120% are the first and second relative orientations. In this regard, a minutiae pair # is positionally distinct iff d(¥%) > 0. For a minutiae template T, M2(T) may be the set of all positionally distinct minutiae pairs drawn over T.

Letting a be a transformation, m a minutia and T a minutiae template. The transformation a(m) of a minutia m, is the minutia obtained by transforming the position and orientation of m by a, and with the same type. Then oT) is defined as the template leim cme By a “standard translation”, is meant any finite sequence of 2-dimensional rotations and translations.

Letting a be a standard translation and #} an n-tuple in the form of a minutia pair.

It will be appreciated that d, rei, rez are invariant under standard transformations, for example, for a minutia pair ft and a standard transformation a:

dis; = diam, oid roda], toziNtj == ropladmil

It will be noted that © and © are type-identical if #05 = 882 and Milt = Bijz, ‚ denoted ® = ® and with 1 2x fin a conventional manner. The co-pair of i is the minutia pair © 2.819) | denoted as coh). domi} = di),

Zico) = iF IS, vn icoirBij == rap IS, 5 roplomia}} om rijs ISD, wherein the set of all minutia pairs encountered in real-world scenarios under consideration is denoted as M? and is called the minutia pair space.

A minutiae tuple or n-tuple ® == Mi... aX may be positionally distinct if, fori # J, the minutiae pair Lg positionally distinct. For a minutiae template T, let MT) denote the set of all positionally distinct minutiae tuples drawn over T. The set of all minutiae n-tuples encountered in the “real-world” scenarios under consideration is denoted

M", and called the minutiae n-tuple space.

It will be understood by those skilled in the art that the symbol/characters/nomenclature if may refer to a minutia n-tuple, i may refer to a minutia pair, and m may refer to a minutia. The same is true, depending on the context, for other symbols/characters/nomenclature used herein.

The hash function may typically be a cryptographically secure hash function H, such as a SHA256 function, which takes an input message, data object, byte-array, binary string, or dataset, as an argument and produces a suitable digest. The hash function H may take any finite number of objects of any type as argument. In this regard, the method may comprise naturally and/or deterministically converting these objects into byte-arrays and concatenating the same into a single byte-array. Digests on the other hand are n-bit strings or ¥ - length byte-arrays, wherein n is a fixed constant determined by H, called the dimension and denoted as H.dim.

The hash function should be pre-image resistant, i.e., given a digest it is (computationally) infeasible to find a message with that digest, second pre-image resistant, i.e., given a message it is infeasible to find another message with the same digest, and collision resistant, i.e., it is infeasible to find two different messages with the same digest.

In this regard, the hash function H should be correlation resistant. This is key to the security of the present disclosure. In this regard, this may be defined as follows: for every n>Oandé : Af" — {0,1} that is non-constant over 4" wherein M is the message space, and for all digests h…… hx, wherein » = A, zal A = Him). for some secret messages ms, ‚Mx, it should be infeasible to determine the value of iii for any iy, . . . in ¥ {Ln ®t whereby M' is the set of all n-tuples over M.

In the present disclosure, the received minutia template as a data set may be partitioned into finitely many equivalence classes together with an indexing of these equivalence classes with the UCIs described herein.

An indexed partition P of a universe © # £ of integral resolution r > 1, is determined by any function p.idx from X onto an index set #1...» 1: The universe is denoted as

P.uni, the resolution is denoted P.res and the index set is denoted P.indices.

Example 1: In an indexed partition P the real interval [0, 100) of resolution 10 is given by Fiadeizy = adsl) mod 10.

For i ¢ Findices | Pi] denotes the pre-image FO U je

FliFiws A: Pa 7% called the (equivalence) class determined by index i. Hence, 2 PUPS The array-like notation is purposefully provided.

An indexed partition may be defined simply by listing its classes in index order. The

UCIs may thus be ordered indices corresponding to the classes. Hence, P is the indexed partition defined by P[Q], . . . ,P[P.res — 1].

Example 2: In the previous example, P[i] = [10i, 10(i+1)}, hence the classes are, in indexed order, [0, 10), [10, 20),...,[90, 100).

It will be noted that = = +91 ie. P(a) is the unique class containing x, i.e., <2 Fix}. Functional notation is used here and thus distinction may be made between dx}. FL aad BOL

Example 3: in the previous example, #{73.22}=[70, 80).

It will be appreciated that the present disclosure may be based on a Bozorth3 fingerprint matching system. For each minutia pair *% from T and each minutia pair # from U, (by convention both positionally distinct) define a Boolean function M=? defined by Malini = toef

WG lB ww bod) «ral ww a

SE wg wy mi iL

We call Ms the Bozorth3 match function. Note, Mai5t Blijf == Ò gnd there exists a standard transformation a such that «8419 is close to 1 and =iID is close to HL, close in position and orientation, within tolerances determined by dand *.

Comparing templates T and U by counting matches may be effective but yields a poor EER (equal error rate), of around 0.33 by experiments. Such a high EER is obtained because while each matching pair must have a matching transformation, different matching pairs may have different transformations.

T and U should thus only be matched if there exists a (single) standard transformation a, such that many of the minutiae of U lie close to (and match type) those of a(T).

It has been observed that longer distances tend to vary more, while relative orientations tend to vary less the longer the distance. In this regard, the present invention as disclosed herein seeks to exploit this observation.

With d be the largest distance between two minutiae, determined experimentally, the method may comprise partitioning a real interval [0, d+1) into M contiguous subintervals

HO = a HE ed) HM Ul = Pare di) For de fias > let I(d) denote the unique index i with 2 Hel A M-length array of distance tolerances multipliers m4 and an

M-length array of relative orientation tolerances multipliers m,, all of which are arrays of positive real numbers are provided, wherein a function

MS sn, 5} == True il, letting im Hegt ff, ADL, is defined and

Wim dingy <= Omg = 8, om} ron) oc mlijxes olm) roi «mali xe

Mios 6, . . Voi gual ae med en mei AF

In terms of the aforementioned observation = faith = mali = mg 4 1}, meld mei om Ii 1

Ideally the matching described above may be on a cycle basis. In this regard, for a cycle of length j, is meant distinct minutiae my, ..., m; from a minutia template T and distinct minutiae ny,..., nj from U such that Maica Mori= 1, j-1 and Mines Ge id

It will be noted that a cycle of length j ensures that the same standard transformation maps j minutiae of T “close” to j minutia of U.

The number of cycles of length greater than 2 is determined using standard graph theoretic techniques, and a matching score determined from the number of cycles and the length of these cycles. The higher the matching score, the better the original fingerprints match.

However, finding cycles is relatively slow. In this regard, it will be noted that for any two minutiae pairs si and *: potential values for the translation are given by: rig, MN) == Nig milly til, B} == AZ]p - W{3p ‚ and three potential values for the rotation are given by: wi) == Be ille, on) =Alle lln, rorim, A} oe ZIN LR), ‚ wherein ‘3 is defined above.

It will be noted that assuming that Mum: then hide dai gnd sty ii Ei) oe rated FEY rod, RY /

For each minutiae pair #t from T, and each minutiae pair i from U, define

Min u. Dn 5 and eo UUR tis, 8) o IOI) mv rota{¥h, 6) a ron, fi

In this regard, if iff}, 88,8 may be defined as some function of th: i#. i and trizin, A, HRY may be defined as some function of "2678, 8}, rete, B}, and Foti, i}

Some clustering technique may be used to divide the matching pairs “2% (i.e. distinct pair st is drawn from T, distinct pair #* is drawn from U, and SM: 6} = frie) with

MA = trues into clusters with respects to translation #1. 8 and rotation * 1%: fi,

A matching score may be derived from the number of members of the cluster with the most members, together with information on the size of T and U.

In any event, the unit-digest and/or the hashed template generated in a manner described above may serve to match one or more stored enrolled hashed templates in a database for purposes of identification, verification, and/or authentication, in use. Instead, or in addition, unit-digest or the hashed template may be used as a basis for further hashed templates which may be derived from the generated unit-digest and/or hashed template.

From the foregoing, it will be appreciated that determining the UCI for each n-tuple is based on attributes of the n-tuple selected from a group comprising type/s of each minutia of the n-tuple, distance/s between each minutia of the n-tuple, and relative orientation/s of minutia of the n-tuple.

The method may comprise: providing a distance partition having a plurality of distance sub-intervals, wherein each sub-interval is associated with a unique distance identifier (UDI); providing an angle partition having a plurality of angle sub-intervals, wherein each angle sub-interval is associated with a unique angle identifier (UA); and wherein determining the UCI of each n-tuple is based on at least one of type/s of minutia in the n-tuple, a UDI of the at least one minutia pair in the n-tuple, and UAls of the relative orientations of the at least one minutia pair in the n-tuple.

The method may comprise:

providing a map from UDIs to a plurality of angle partitions, wherein each angle partition has a plurality of angle sub-intervals, and wherein each angle sub- interval is associated with the unique angle identifier (UA); and wherein determining the UCI is based on at least one of the types of minutia in the n-tuple, UDI of the at least one minutia pair, and UAI of relative orientations of the at least one minutia pair in the angle partition determined by the UDI of the at least one minutia pair in the map.

Determining the UCI for each n-tuple of the plurality of positionally distinct n-tuples may comprise: determining a distance between minutiae of the at least one minutia pair; determining a UDI of the at least one minutia pair, wherein the UDI is an identifier of the sub-interval of the distance partition containing the determined distance; determining a first relative orientation angle of the at least one minutiae pair; determining a second relative orientation angle of the at least one minutiae pair; determining a first UAI of the at least one minutia pair, wherein the first UAI is an identifier of the sub-interval of the angle partition determined by the determined

UDI and the map, containing the determined first relative orientation angle of the minutiae of the at least one minutiae pair; and determining a second UAI of the at least one minutia pair, wherein the second UAI is an identifier of the sub-interval of the angle partition determined by the determined UDI and the map, containing the determined second relative orientation angle of the minutiae of the at least one minutiae pair; determining a first type of identifying data associated with one minutia of the at least one minutia pair, from at least two different identifying data types; and determining a second type of identifying data associated with another minutia of the at least one minutia pair, from the at least two different identifying data types;

wherein determining the UCI is based on one or more of the determined UDI, the first and second UAI, the first type of identifying data, and the second type of identifying data.

For n-tuples with a plurality of minutiae, the method comprises performing the method for each consecutive distinct minutia pair in the n-tuple. For example, for a 5-tuple, i.e., n= 5, the method may comprise performing the method for minutia pairs consisting of minutia 1 to 2, 2 t0 3, 3to 4, and 4 to 5, i.e. for a number of minutia pairs determined by n- 1.

For each n-tuple, the method may comprise: determining a distance remainder hash, by: determining a distance remainder associated with the at least one minutia pair; combining the determined UDI, the user password, and a distance remainder salt into a combined distance remainder dataset; hashing the distance remainder dataset with a hash function to obtain a distance hash; applying a hash-transformation to the distance hash, wherein the hash-transformation maps the distance hash to a real number; and adding the determined distance remainder to the hash- transformation of the distance hash, and rounding the resultant sum to a first predetermined number of decimal places to yield the distance remainder hash; determining a first relative orientation remainder hash by: determining a first relative orientation remainder associated with the at least one minutia pair; combining the determined UDI, the user password, and a first relative orientation remainder salt into a combined first relative orientation remainder dataset;

hashing the first relative orientation remainder dataset with a hash function to obtain a first relative orientation hash; applying a hash-transformation to the first relative orientation hash wherein the hash-transformation maps the first relative orientation hash to a real number; and adding the determined first relative orientation remainder to the hash- transformation of the first relative orientation hash and rounding the resultant sum to a second predetermined number of decimal places to yield the first relative orientation remainder unit hash; determining a second relative orientation remainder hash, by: determining a second relative orientation remainder associated with the at least one minutia pair; combining the determined UDI, the user password, and a second relative orientation remainder salt into a combined second relative orientation remainder dataset; hashing the second relative orientation remainder dataset with a hash function to obtain a second relative orientation hash; applying a hash-transformation to the second relative orientation hash, wherein the hash-transformation maps a range of the second relative orientation hash to a real number; and adding the determined second relative orientation remainder to the hash-transformation of the second relative orientation hash, and rounding the resultant sum to the second predetermined number of decimal places to yield a second relative orientation remainder hash; and; generating a unit-hash comprising the unit-digest, the distance remainder hash of the at least one minutia pair, the first relative orientation remainder hash of the at least one minutia pair, and the second relative orientation remainder hash of the at least minutia pair.

It will be appreciated that in example embodiments wherein n22, the generated unit hash may typically comprise the unit-digest, and distance remainder hashes, first relative orientation remainder hashes, and second relative orientation remainder hashes for multiple minutia pairs of the n-tuple.

The method may comprise: determining the distance remainder by determining a difference between the determined distance of the at least one minutia pair and a lower bound of a sub- interval of the distance partition containing the determined distance; determining the first relative orientation angle remainder by determining a difference between the first relative orientation angle of the at least one minutia pair and a lower bound of the sub-interval of the angle partition comprising the first relative orientation angle; determining the second relative orientation angle remainder by determining a difference between the second relative orientation angle of the at least one minutia pair and a lower bound of the sub-interval of the angle partition comprising the second relative orientation angle; and generating a sharpened unit-hash comprising the unit-digest, the distance remainder hash, the first relative orientation remainder hash, and the second relative orientation remainder hash.

The method may comprise collecting the generated sharpened unit-hashes into a sharpened hashed template.

The method may comprises: determining the distance remainder by: providing a compactification factor based on the determined UDI; determining a compactification value by determining a sum of the determined distance between the minutiae of the at least one minutia pair, and a product of the determined compactification factor and a difference between a midpoint of the sub-interval of the distance partition containing the determined distance and the determined distance; and determining the distance remainder by determining a difference between the determined compactification value and the lower bound of the sub-interval of the distance partition containing the compactification value; determining the first relative orientation angle remainder by: providing a first relative orientation compactification factor based on the determined first UA; determining a first relative orientation compactification value by determining a sum of the determined first relative orientation value, and a product of the determined first relative orientation compactification value and a difference between a midpoint of the sub-interval of the angle partition containing the determined first relative orientation angle and the determined first relative orientation value; and determining the first relative orientation angle remainder by determining a difference between the determined first relative orientation compactification value and the lower bound of the sub-interval of the angle partition containing the first relative orientation compactification value; and determining the second relative orientation angle remainder by: providing a second relative orientation compactification factor based on the determined second UAI; determining a second relative orientation compactification value by determining a sum of the determined second relative orientation value, and a product of the determined second relative orientation compactification value and a difference between a midpoint of the sub-interval of the angle partition containing the determined second relative orientation angle and the determined second relative orientation value; and determining the second relative orientation angle remainder by determining a difference between the determined second relative orientation compactification value and the lower bound of the sub-interval of the angle partition containing the second relative orientation compactification value;

‚and generating a compact unit-hash comprising the unit-digest, the distance remainder hash, the first relative orientation remainder hash, and the second relative orientation remainder hash.

The method may comprise collecting the generated compact unit-hashes into a compact hashed template.

For each n-tuple, the method may comprise: providing a label for each minutia of the minutia template; and combining the unit-hash with the n-tuple of labels for each minutia of the minutia n-tuple.

The method may comprise: determining a translation property to be added to each unit-hash, wherein the translation property is a point having an x component and a y component, by: providing a translation determinant function; deterministically mapping the n-tuple to an absolute point using the translation determinant function provided, wherein the absolute point has an absolute x component and an absolute y component; combining the UCI, the user password, and an x component organisational salt into a combined x component mapped dataset; hashing the x component mapped dataset with a hash function to obtain an x component mapped hash; applying a hash transformation to the x component mapped hash to obtain an x transformation; adding the absolute x component to the x transformation, and rounding the resultant sum to a first predetermined number of decimal places to yield the x component of the translation property; combining the UCI, the user password, and a y component organisational salt into a combined y component mapped dataset;

hashing the y component mapped dataset with a hash function to obtain a y component mapped hash; applying a hash transformation to the y component mapped hash to obtain a y transformation; and adding the absolute y component to the y transformation, and rounding the resultant sum to the first predetermined number of decimal places to yield the y component of the translation property; determining a rotation property to be added to each unit-hash, by: providing a rotation determinant function; deterministically mapping the n-tuple to an absolute angle with the provided rotation determinant function; combining the UCI, the user password, and a third global salt into a combined angle mapped dataset; hashing the angle mapped dataset with a hash function to obtain an angle mapped digest; applying a hash transformation to the angle mapped digest; adding the absolute angle to the hash transformation of the angle mapped digest; and converting the resultant sum to a form from 0° to 360° and rounding the converted resultant sum to a first predetermined number of decimal places to yield the rotation property to be added to the unit-hash; ‚and combining the unit-hash, the translation property, and the rotation property into an absolute unit-hash.

The method may comprise collecting the absolute unit-hashes into an absolute unit- hashed template.

The method may comprise receiving user specific data; and combining the user specific data with the received password prior to hashing. The user specific data may be any data specifically associated with the user and may comprise a user identifier, or any other user specific data which may be used for the purposes described herein, for example, a user's first or last name, their identity/social security number.

According to another aspect of the invention, there is provided a method of matching hashed templates, wherein the method comprises: receiving a hashed template generated in a manner described above; comparing the received hashed template to one or more hashed templates stored in a database; and determining a match based on a degree of unit-digests of the received hashed template in common with the one or more hashed templates stored in the database.

Differently defined, from the foregoing, there is provided a method for hashing a fingerprint minutiae data T , i.e., data from any minutia template, such as obtained from a fingerprint scanner, a user password pw, which can be any string/byte-array, ideally concatenated with fixed user identifying information in order to prevent a common password attack, and a fixed organization specific salt Sr | referred to as the root salt, where salts are any string/byte-array into a set H called the hashed template, which can be transmitted, stored and later used, wherein the method comprises: (A) determining a set of distinct minutiae pairs from the template, possibly restricted by distance, referred to as the elected pairs; (B) for each minutiae pair 1 in the set: (i) determine the index i of the equivalence class containing m in an indexed partition of all possible minutiae pairs, where membership is determined purely by - the type of the first minutia in the pair, i.e., bifurcation or ridge- ending, - the type of the second minutia in the pair,

- the distance d(f}) between the two minutiae, - the first relative orientation "(Mie the relative orientation of the first minutiae in the pair, - the second relative orientation 2 U) © ie, the relative orientation of the second minutiae in the pair, noting that such an index must be both translation and rotation invariant; (ii) combining each index, with the user password pw and the organizational salt s,, and converting the result to a byte- array/binary-string; iii) hashing each byte-array/binary-string with a cryptographically secure hash function, such as SHA2586, obtaining the unit- hash, noting that the unit-hash is both translation and rotation invariant; ©) collecting all the unit-hashes in a set, which is the hashed template, with optional co-pair reduction.

Most generally, the hashed template may be determined by the cryptographic hash function H, a dimension # 2, an integral index-bound 0 < b, and an index-function wh} from MP? into the integral [O, b), such that for any standard transformation a and positionally distinct minutiae tuples Af, imi = ddladRiy

As mentioned above, the index i referred to herein is typically the UCI defined herein. It will be appreciated to those skilled in the art that indexing a finite set A, means a bijection from A onto & tel,

The method may comprise using the hashed template, or a hashed template based on the hashed template above, for one or more of identification, verification, and authorisation of the user associated with the fingerprint minutia template.

The index i or UCI of a minutia pair i! in the selected set described above may be determined as follows: (a) determining a distance index ig which is defined as the index of the subinterval containing the distance 40%} in an indexed partition D called the distance partition, of the interval [O, d +1) into contiguous subintervals, where d is the maximum possible distances between minutiae;

(b) determining the first relative orientation index ii which is defined as the index of the sub-interval containing the first relative orientation ©:{%! in an indexed angle partition Oia} where each ©ilis a partition of angles into contiguous subintervals, calling © the relative orientation partitions; (c) determining the second relative orientation index in2 which is defined as the index of the subinterval containing the second relative orientation ©: { fh) in the angle partition ©}; {d) determining the first type index in which his defined to O if the first minutiae of the pair is a bifurcation, and 1 otherwise; (e) determining the second type index ip which is defined to O if the second minutiae of the pair is a bifurcation, and 1 otherwise; (f) determining the index i which is defined as: es ERE bd Ng, + dip, + Jy + hy, , wherein N is the maximum number of sub-intervals of any Ola)

Example 4: Assume that the maximal real-world distance between two minutiae is just below 500. Define an indexed partition D by [D, 50), [50, 100), . . . , [400, 450), [450, 500), called the distance partition, and an indexed angle partition O defined by [0, 360), [36, 72), ...,[324, 360), called the relative orientation partition. Then for each minutiae pair *® ‚the index i or ifs defined as: di = JON dl, dk PD dy where the distance index i = Pidxidimiy the first relative orientation index jo, = Qdx{rou{3) the second relative orientation index im: ChiSXIrOz{N} the first type index * BA the second type index * * ®iiit In this example, b= 4000. It will be appreciated that the entropy e of the system is the number of non-trivial indices, wherein iv {is called trivial if 17 {3} = else it is non-trivial. The security of the teachings herein lies in the entropy and ** * Moreover, it will be noted that an index is biometrically uniform if, for many minutia pairs drawn over many representative minutiae templates, each non-trivial index should account for a similar number of minutiae pairs.

It will be appreciated that the partition D and array of partitions © are fixed parameters. Moreover, the distance index iy may be the UDI described herein and the first and second UAI may be the first and second relative orientation angle indices. Similarly, the first and second type of identifying data may be the first and second type indices as defined herein.

It will be appreciated that since differences in distances are greater with longer distances, the sub-intervals in the distance partition may be bigger for the longer distances.

Since relative orientations tend to vary less the longer the distance, the angle intervals may be smaller the larger the distances. It follows that the angle and distance partitions may thus be related. In particular, the number of angle sub-intervals may depend on the particular distance. It is the number of angle sub-intervals since there is no reason relative orientation sub-intervals should be of different size within in any one relative orientation partition. In this regard, the distance partition D may have intervals of different lengths/sizes. The relative orientation partition may be an array of relative orientation partitions, indexed by the distance index.

The distance partition may be an indexed half-open partition D. The indexed basic- angle partition may be an indexed half-open partition. of the interval [0, 360). The sub- intervals may be large. In some example embodiments, the distance intervals may be of length ¢, and all relative orientation intervals may be of length ¢ .

The basic-angle partition may be an indexed half-open partition of the interval [0, 360). An indexed angle partition A is determined by an indexed basic-angle partition which may be denoted as A and a small positive angle denoted A.sh, where A.sh is strictly smaller than the length of any equivalence class of A Those skilled in the art will appreciate that different nomenclature used herein may refer to the same aspects, as the case may be.

In any event, the hasher as described herein is parametised by an indexed half- open distance partition D of the interval[0, d+1), where d is the maximum distance between two distinct minutiae drawn from real “real-world” templates. The hasher is further parameterised by the M-length, wherein 3 + D=, array of of relative angle partitions ©.

N may be defined to be maxifkires : kw 8,1, M3 Each ol may be simple, although perhaps each differing in resolution.

Differently defined, the method may comprise, for each minutiae tuple or n-tuple m, determining the index i or id(m) as follows: (iy) for kx n= define or determine:

WAL A Dadx{HsE E+ UE, foo th] Olle he jk & + U, called the k-th distance index, the k-th first relative orientation index and the k-th first relative orientation index, respectively, and for 3 *: kx 1 1, determine or define: fff] = ikl called the k-th type index, (ii) define #5 py

ANBO] NL Jd JD + 24001 en] (iii) recursively define ik for Laid sta 2 py

OMANTETRD a NRR] ON a ijk] . and (iv) determine or define the index iii: as: {MY dj 1

As described herein, this index is standard transformation invariant. It will be noted that the n-1 data is excluded since this is already implicit (consider the 2-dimensional case), and unnecessary class mismatch errors are avoided from being added.

With a standard transformation invariant notion of index, the present disclosure permits that the index is hidden and any correlations between indices are hidden, by hashing each index together with the user password and organizational salt, via hashing with the function H.

In one example embodiment, the method may comprise reducing the number of members of a family to include in the hashed template, that must be invariant under standard transformation. Ideally this may be a reduction to a single representative. By family Tend} of distinct minutiae n-tuple % = Uma... a. js meant the set of all distinct minutiae n-tuples over Fe Pes,

The method may comprise providing a choice function $51} : AM” > A1" sch that for all fie Af" , and all B¢ fami) chii = AUD, The method may comprise letting fas ng) denote the set of all sim} | such that for all

Sew ef), ii) = JRL An n-tuple m is resolvable if fauna = &

In the case of the n-tuple which is resolvable, the choice function chsicai i may be a unique member of fr. with the lowest index. Such a function must be a choice function, However, this reduces entropy by a factor of nl. To avoid this, the method comprises introducing a reduction-oracle orc(n,h) as a parameter, that takes a natural number n and a hash-digest, such as a unit-digest, as input, and (as) uniformly (as possible) outputs an integer in the interval [0, n).

Example 5: One such oracle is defined by ‘tin, == & mod n, viewing the digest h as a large integer.

Consider the following choice function 55:35. 9%}. which requires an additional organizational salt Ss: . Assuming that the n-tuple is resolvable. 1. Let { be the unique family identities Hits wail a5 a sequence in strictly increasing numeric order; 3. Let A= Hi se. pit 4 Let = orci hl and 5. Define choc: pw! to be the (unique) member of fam(m) with index i.

With families reduced in such a manner, the hashed template size is reduced by n!, while maintaining the entropy, without exposing the password by the inclusion of Hin step

2. The trade-off is a bet that index mismatch occurs for no member of the family, where the probability of mismatch grows with dimension.

It will be appreciated that the family of a minutia pair ¥, consist of # and its co-pair co(®%). The method may comprise reducing co-pairs by applying a suitable co-pair reduction function ch’. For a reducible minutiae pair #, the co-pair reduction function = may be defined as follows: in fie wile

Cs YEO a ili ch Bi | oh HOLY id ’ {on BY, otherwise, {iy otherwise, ce { a. {mn icf) ei {fy : / {Coli}, otherwise,

The method may comprise processing a hashed digest with a Boolean oracle which outputs either true or false.

Example 6: A Boolean oracle is defined by orc’(h) = true iff the first bit of h = 0.

For reducible #, define “HH: Se. wi py: { chil, or Hind BEB}, kool}, 80. purl 1 cold), otherwise.

The method may comprise, for each minutia pair 77 in the selected pairs: {i determining the distance index is and the unit hash h as described above; ii) determining the distance remainder ra = “mei where, for any distance x, mnia)} =p, ‚ where b is the greatest lower bound of the distance partition subinterval containing x; iii) determining ha by combining dish pw and sq, converting the result to a byte array and hashing with the chosen cryptographically secure hash function

H;

(iv) determining or defining *¢ © “hal wherein “is uniform full- hash-transformation, where a full-hash-transformation - is a mapping of the range of H into the real interval {= © 4 to 2.85 decimal points; for convenience fy =

CES

(v) determining or defining 3 ~ ¢ (vi) determining or defining "i to be the rounding of Tito fa decimal places; (vid) determining or defining the first relative orientation remainder

Fay MOIGNTOIEN) here, for any angle partition A and angle 8, rma(8) is defined analogously tc ii. above, but taking care when an interval straddles 0; (vii) determining or defining hot by combining ‘©&®, pw and Sa, converting the result to a byte array and hashing with the chosen cryptographically secure hash function H; (ix) determining or define 3x 7% Zwi where “itis a uniform half- hash-transformation into the real interval [0, 360), where a half-hash-transformation “is a mapping of the range of H into the real interval [0, =.{ ) to “3 decimal points; for convenience tv = Heres. oa eR (x) determining or defining xT Tee ® Bex. (x) determining or defining 7e “32°, } wherein 328% is the function that converts any angle 8 to its equivalent value in the interval [0, 360); (xii) determining or defining *% to be the rounding of ‘= to * decimal places; (xiii) determining or defining the second relative orientation remainder

Po ION {rollin (xiv) determining or defining hoz by combining ‘3, pw and Sw converting the result to a byte array and hashing with the chosen cryptographically secure hash function H;

(xv) determining or defining 3 © Fife (xvi) determining or defining "= TF; (xvii) determining or defining 7x: * #63; (xviii) determining or defining "= to be the rounding of ‘“ to f, decimal places; and (xix) determining or defining an object h with properties »%¢ = >» feard ra heei ol gnd Bane rl referred to as a sharp unit-hash determined by ¥t and pw.

In other words, the method may comprise adding dst, 9:09}, and eelt), or rather, their remainders modulo their sub-intervals, or rather these remainders shifted by some value determined by a digest transformation of the hash of WM the password pw, and the three additional salts.

It will be appreciated that the half-hash-transformation = of length =.i and resolution “* js a function from the digests of H into the real interval [0, 2) to “7. decimal places.

In other words, a half-hash-transformation :: of length wd = 9 and resolution r denoted ‘88, js a function from the domain of H into those real numbers in the interval [O, n) with at most r decimal points.

A full-hash-transformation* of length wd == 72 and resolution =:*. is a function from the digests of H into the real interval i 24% to zr, decimal places.

The method may comprise collecting all the sharp unit-hashes into a set, with optional co-pair reduction, called the hashed template determined by minutiae template T and password pw.

The method may comprise providing the distance partition D with sub-intervals of differing lengths. The method may comprise determining the particular relative orientation partition based on the distance index. In other words, the particular relative orientation partition is based on the distance index.

In one example embodiment, the method may comprise:

re-defining the distance remainder as 3 © 2 URL Cll herein iy is the distance index, Ca is an array of compactification percents, which are real numbers greater and equal to 0 and strictly less than 1, called the distance compactification, and where, for any distance d and compactification percent c, enig el) = red Faoptid, et, i. : rapide} = mp aptid, ei). wherein | is the distance partition sub-interval containing d, and where, |.cpt(d, c) is the compactification of d into interval |, defined by Zeptid.e) =d + elm dl), wherein m is the midpoint of the interval I; re-defining the first relative orientation remainder as

Po, = Me roy IY, Caliah . . ie © ogg roy Celia] , wherein Cy, is an array of compactification percents, called the relative orientation compactification, wherein ment #2} is defined analogously to Mep id ©} above but taking care with the angle subinterval containing 0; and re-defining the second relative orientation remainder as

Ves gp 0a Leie]. wherein the sharp unit-hashed obtained in this fashion are referred to as compact unit-hashes.

By way of example, for an interval [0, 100]. A 50% compactification percent should map into [25, 75], a 25% compactification percent should map into [12.5, 87.5], a 75% compactification should map into [37.5, 62.5], while a 0% compactification maps into [0, 100].

In the case that all distance and relative orientation compactification percents are precisely 1, this method coincides with the method described above. Moreover, it will be appreciated that the C4 and C may be parameters to the method. Moreover, the salts s,,

Su, Sro1, and Sz May all be organisational salts, which are fixed. In addition, “a is a fixed parameter.

It will be appreciated that to perform cycle checking, the method may comprise labelling/numbering/ordering minutiae of a minutia template; and recording the label of the minutia that comprise the hashed par. The method may comprise labelling/numbering/ordering the minutiae in the minutia template prior to hashing.

In one example embodiment, the method may comprise, for each sharp unit-hash, h, the method may comprise: adding two properties to the sharp unit-hash, namely:

Beda GRO), hj = ding}, , wherein a random bijection |, called the random ordering, from T onto {5,711 and wherein the new object is referred to as the labelled unit-hash.

The method may comprise forgetting the random ordering; and collecting the labelled unit-hashes into a labelled hashed template.

In another example embodiment, the method may comprise, for each selected pair the method may comprise: adding a property, A.F to the sharp-unit hash, h, which is an array of length

D den where, for each #5 & «Ten, BFE jg determined or defined by: (a) determining ‘2% = TX} | wherein each TIK) is a function called a translation determinant mapping a minutiae pair to an absolute point; (b) determining or defining Ag by combining |, pw, and organisational salt S*j, converting the result to a byte array and hashing with a cryptographically secure hash function H; (©) determining or defining $= = wif} wherein “wis a uniform full-hash-transformation, for convenience hm VnolES: (d) determining or defining « +2; (e) determining or defining 2" to be the rounding of x’ to fx decimal places; (f) determining or defining hy by combining i, pw and organizational salt Sylk]. converting the result to a byte array and hashing with the chosen cryptographically secure hash function H,

(9) determining or defining define 8 = Ji), wherein “= is a uniform full-hash-transformation: for convenience i = “r128. (h) determining or defining ¥ © Ye; (i) determining or defining ¥ to be the rounding of y to fy decimal places; and 1) determining or defining f-F1 = Ta adding a property #.4 to the sharp unit-hash, h, which is an arrange of length Fen wherein for each B & « Hien. RAR jg determined or defined by: (a) determining # = Bilis: wherein each Riis a function called a rotation determinant mapping a minutiae pair to an absolute angle; (b) determining define he by combining i, pw and organizational salt sal] ‚ converting the result to a byte array and hashing with the chosen cryptographically secure hash function H; (c) determining or defining ™¢ 7 {fe} wherein Ze is a uniform half-hash-transformation into [0, 360), wherein bx = Bres: (d) determining or defining © © 2%; (e) determining or defining © * SH (f) determining or defining #“ to be the rounding of & tof decimal places; and (9) determining or defining »-i&i = # which is an object referred to as an absolute unit-hash.

It will be appreciated that the absolute hashed template may add the following parameters to the compact hashed template, or may extend the compact hashed template, with the following parameters: an array T of translation determinants; an array R of rotation determinants, a uniform full-hash-transformation “= | a uniform full-hash-transformation *v« ‚ and a uniform half-hash-transformation ‘ts into [0, 360).

The salts Sand Sy may be a T-length arrays of distinct salts, wherein the salt Sa may be a R-length array of distinct salts.

The method may comprise collecting all the absolute unit-hashes into an absolute hashed template.

For completeness, a translation determinant B) may be a function mapping a minutiae n-tuple Fito a point, such that, for two minutiae n-tuples and #1, 206 realises some aspect of the translations from to 1. In other words, p maps to an absolute point. On the other hand, the rotation determinant al} may be a function mapping a minutia n-tuple Tito an angle, such that, for two minutia n-tuples and i U al realises some aspect of rotation from ito A. In other words, 2i8ì} maps % to an absolute angle.

The arrays T of translational determinants and R of rotational determinants, =, “ry , and ©8 are parameters of the method described herein.

According to another aspect of the invention, there is provided a processor- implemented method for comparing two hashed templates, H and K, to determine a non- negative real value score such that if the hashed templates where generated from different passwords or different salts, then the score is 0 with cryptographically high probability, otherwise, if generated from the same password and salt, the score increases the better the determining fingerprints match, wherein the score (H, K) is determined or defined as: if B" A = 13 then is score is defined to be 0, otherwise, the score is determined by standard statistical techniques, comparing the size of &# “: & with the sizes of H and K, together with experimentally obtained statistical data, such as expected sizes of # + & for the same finger and for different fingers, etc. very simple example is defining the score to be Ho KymwgiB IR

It will be understood that matching may essentially be a test for unit-digest equality, which, with cryptographic probability, is equivalent to testing for index equality.

In the example embodiment wherein, the hashed templates H and K are compact or sharp hashed templates, the score (H, K) is determined by, or defined as follows:

for each unit hash ® « # andunithash & © #& define a unit_match (h, k) if: dg = hag, had keda A, sr cds) en © and

SE SE «0 s ; and calculating Can {he Huot _satchih, kj for ace doa Ki otherwise the score is determined by standard statistical techniques, comparing the size of C with the sizes of H and K, together with experimentally obtained statistical data, such as expected sizes of C for the same finger and for different fingers, etc.., one very simple example is defining the

In the example embodiment wherein, the hashed templates H and K are labelled hashed templates, the score (H, K} is determined by, or defined as follows: determining bo {hihdnhikis oi hoo SE Koundt_matchih, &3} , and letting G be the set of all the first pairs of L, and let H be the set of the second pairs, observing that G (resp. H) may be viewed as a graph whose elements are the minutiae of H (resp. K) as identified by their random orderings, with an edge linking two minutiae if that minutiae pair matches a “pair” in K (resp.K), in which case

L maps a matching edge of G to the associated matching edges of H; if L is empty then the score is defined to be 0, otherwise, the method may comprise using standard graph theoretic techniques to find the maximal cycles of length 3 or more of graph G that map via L to cycles in H of the same length, called the maximal matching cycles; and generating the score using standard statistical techniques, comparing a length-weighted tally of the maximal matching cycles with the sizes of |H| and |K|, together with experimentally obtained statistical data regarding expected values for positive and negative matches, etc.

In the example embodiment wherein, the hashed templates H and K are absolute hashed templates, the score (H, K) is determined by, or defined as follows: (A) a sanity check is performed to ensure that for every

Re Had bo K, APln = pg = A. Pden and A Alen = fn, = RAJ, for some fixed np and na, and if not, the score is defined to be 0, otherwise, (B) foreach? = H snd & © K define sl match™ th kijf (i) unit _matchik, ki (ii) the translations FF kij: 8si= Mg 1 al] lie within an acceptable tolerance of each other; and (ii) the rotations {AAU BA] : Ox dnd a ie within an acceptable tolerance of each other; (C) if there exists no fr HH mul no k © K such that weit match {kJ}, then the score is defined to be 0, otherwise; (D) foreach ¢ H and & < A gychthat uni match fh, Rk (i define ti as some representative value of the set of the (similarly valued) translations ‘Pli EPH] : Ds ins th such as taking the average, (ii) define rx as some representative value of the set of the (similarly valued) rotations {hAl - BA]: Gn, 11 such as taking the average, (E) use a statistical clustering technique to divide the pairs ode Boe BD with walt ssi RL into clusters with respects to translation tx and rotation ry. i.e., each cluster contains pairs with similar translation and rotation; and (F) determining the score via standard statistical techniques, comparing the size of the largest cluster, with the sizes of H and K, together with experimentally obtained statistical data regarding expected values for positive and negative matches, etc.

The translational and rotational tolerances are parameters of the method described herein.

The method may comprise, for a distinct minutiae n-tuple, determining a unique candidate n-tuple from the n! permutations of :8, for inclusion in the hashed template, provided at least one permutation has an index distinct from the indices of the other permutations, by: (a) ordering the labels of all permutations of the tuple and removing any labels that do not appear only once, obtaining the ordered unique labels list (OULL); (b) combining the first label of the OULL, an organisational salt specifically for this purpose, and the user password into a data unit, and using cryptographically secure hash function to hash this combined data unit, obtaining the choice digest; (©) using a deterministic oracle to determine a position (index) into the

OULL, from the choice digest and the size of the OULL only; (A) finding the index in the OULL at this position; and (e) choosing the unique permutation with this index.

The method may comprise, for a distinct minutiae pair <>: determining which of the pair or its reverse *# to include in the hashed template, provided the pair and its reverse have distinct indices, as follows: (a) a simple choice is determined as follows: (i) if m and n have different types, then, if m is a bifurcation, then the simple choice is ‘225 otherwise, the simple choice is **:: and (ii) otherwise, if the label of ‘>: is comparatively less than the label of #72, then the simple choice is *%*, otherwise, the simple choice is Can

(b) combining the least (say) of the indices of ‘=> and “#2 an organizational salt specifically for this purpose, and the user password into a data unit, and use the cryptographically secure hash function to hash this combined data unit, obtaining the choice digest; (©) using a deterministic oracle that returns either true or false, from the choice digest only; and (d) if the oracles chose true, the simple choice is selected or chosen, otherwise the reverse of the simple choice is selected or chosen.

According to another aspect of the invention, there is provided a system comprising: at least one processor, and a memory device coupled to the at least one processor, wherein the memory device stores non-transitory processor-executable instructions which when executed on the at least one processor causes the at least one processor to perform any one of the methods, or method steps, as described above.

It will be appreciated that the system may be embodied in one or more endpoint or mobile computing devices or one or more servers.

According to another aspect of the invention, there is provided a non-transitory processor-executable storage medium storing processor-executable instructions which when executed on at least one processor causes the at least one processor to implement at least some of the methods, or method steps, described herein.

According to another aspect of the invention, there is provided a server comprising at least one processor and a database communicatively coupled to the at least one processor, wherein the at least one processor is configured to implement at least some of the methods, or method steps, described herein.

According to another aspect of the invention, there is provided an endpoint computing device comprising at least one processor and a memory device coupled to the at least one processor, wherein the memory device stores a software application having instructions which when executed by the at least one processor is configured to implement at least some of the methods, or method steps, described herein.

It will be appreciated that aspects described herein with respect to one example embodiment of the invention may be apply mutatis mutandis to another aspect of the invention described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic block diagram of a system in accordance with an example embodiment of the invention;

Figure 2 shows a flow diagram of a method in accordance with an example embodiment of the invention;

Figure 3 shows another flow diagram of a method in accordance with an example embodiment of the invention;

Figure 4 shows another flow diagram of a method in accordance with an example embodiment of the invention;

Figure 5 shows another flow diagram of a method in accordance with an example embodiment of the invention;

Figure 6 shows a schematic block diagram of an endpoint computing device in accordance with an example embodiment of the invention; and

Figure 7 shows a schematic block diagram of a server in accordance with an example embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The following description of the invention is provided as an enabling teaching of the invention. Those skilled in the relevant art will recognise that many changes can be made to the embodiment described, while still attaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be attained by selecting some of the features of the present invention without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the present invention are possible, and may even be desirable in certain circumstances, and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not a limitation thereof.

It will be appreciated that the phrase “for example,” “such as”, and variants thereof describe non-limiting embodiments of the presently disclosed subject matter. Reference in the specification to “one example embodiment”, “another example embodiment”, “some example embodiment”, or variants thereof means that a particular feature, structure or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the presently disclosed subject matter. Thus, the use of the phrase “one example embodiment”, “another example embodiment”, “some example embodiment”, or variants thereof does not necessarily refer to the same embodiment(s).

Unless otherwise stated, some features of the subject matter described herein, which are, described in the context of separate embodiments for purposes of clarity, may also be provided in combination in a single embodiment. Similarly, various features of the subject matter disclosed herein which are described in the context of a single embodiment may also be provided separately or in any suitable sub-combination.

The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims. For brevity, the word “may” is used in a permissive sense (i.e., meaning “having the potential to”), rather than the mandatory sense (i.e., meaning “must”).

The words “include,” “including,” and “includes” and the words “comprises”, “comprising”, and “comprises” mean including and comprising, but not limited to, respectively.

Referring to Figure 1 of the drawings a system in accordance with an example embodiment of the invention is generally indicated by reference numeral 10.

The example embodiment of the system 10 is described with reference to a financial institution such as a bank wishing to enhance security of their online or digital banking systems, by introducing a degree of proof-of-life using biometrics, over and above existing password security protocols. Neither the bank nor the user wishes to transmit or store biometric data for personal security reasons. Neither would they like to transmit nor store passwords. The present invention provides a means to enhance banking security without having to transmit or store passwords However, this is an example embodiment and should notbe seen as a limitation of the application of the teachings disclosed herein, or as claimed herein.

Reference will be made herein to biometrics is in the form of fingerprints. However, it will be appreciated by those skilled in the art that the teachings herein may be extended mutatis mutandis to other biometrics.

The system 10, or components thereof, may be a standalone and communicatively coupled to a banking system of a bank. Instead, or in addition, the system 10, or components thereof may be part of an online or digital banking system of a bank.

The system 10 includes an endpoint computing device in the form of a mobile computing device 12, such as a mobile phone or smartphone, a tablet computer, a personal digital assistant, a wearable computing device, a portable media player, a computing device of a vehicle, etc.

The mobile computing device 12 includes a processor 14, and a memory device 16 coupled thereto, wherein the memory device 16 stores non-transitory processor-executable instructions and data corresponding to one or more software applications (“apps”). For example, the mobile device 12 may include (i.e., stored in the memory device 16) a fingerprint software application 18 which directs the operations of the mobile computing device 12 as described herein. The processor 14 is configured to execute the processor- executable instructions corresponding to the app 18 and as such reference to operations of the app 18, and components thereof, may be understood to mean operations by the processor 14 or mobile computing device 12 under instructions associated with the app 18, and components thereof. Thus, the processes or methods ascribed to the app 18 may be interchangeably ascribed to the processor 14, and the mobile computing device 12, as the case may be.

The mobile computing device 12 also includes a camera 20, for example, a conventional complementary metal oxide semiconductor (CMOS) camera, or the like to capture images, and a communications module in the form of a wireless transceiver 22 configured to communicate with one or more other devices such as servers over a communications network 24.

The communications network 24 may comprise one or more different types of communication networks. In this regard, the communication networks may be one or more of the Internet, a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), various types of telephone networks (e.g., Public Switch Telephone

Networks (PSTN) with Digital Subscriber Line (DSL) technology) or mobile networks (e.g.,

Global System Mobile (GSM) communication, General Packet Radio Service (GPRS),

Code Division Multiple Access (CDMA), and other suitable mobile telecommunication network technologies), or any combination thereof. It will be noted that communication within the network may achieved via suitable wireless or hard-wired communication technologies and/or standards (e.g., wireless fidelity (Wi-Fi®), 4G, long-term evolution (LTE™), WIMAX, 5G, and the like).

The system 10 may comprise a plurality of mobile computing devices 12 but only one is illustrated for ease of illustration and description.

The software application 18 may be, or may be part of, a mobile banking application that is specific to a financial institution, such as a specific bank or a specific credit union. In other example embodiments, the software application 18 may be a bespoke application which handles the security of the transactions of a conventional banking application.

Whatever the case, it will be appreciated that the software application 18, as it operates on the mobile computing device 12, forms part of the system 10 as described herein. The software application 18 may have a suitable graphical user interface (GUI) with which a user may interact with the same. Moreover, it will be understood that the software application 18 may control at least some of the functionality of the mobile computing device 12 for the purposes of enabling the methodology described herein, for example, the software application 18 may be configured to access the camera 20 of the mobile computing device as will be described below.

The user of the mobile device 12 may download the software application or “app” 18 from an online software application store. In some example embodiments, for mobile banking, the software app 18 may be configured to perform conventional banking operations such as an account balance operation, a fund transfer operation, a credit or debit card payment operation, a deposit operation, a withdrawal operation, a bill pay operation, a transaction history operation, etc.

The system 10 also includes a server, for example, a back-end server 30. Though one server 30 is illustrated, it will be appreciated that in some example embodiments, the system 10 may comprise multiple back-end servers 30, for example, distributed across different geographic locations but in communication with each other, and the mobile computing device 12, via the communications network 24, to support the software application 18 and the operation of the system 10 as described herein.

As alluded to above, the back-end server 30 may form part of a digital banking system of a bank. However, in other example embodiments, the server 30 may be a standalone server which is in communication with a digital system of a bank to provide the functionality described herein, particularly to identify, authorise, and/or validate a user based on their fingerprints.

The back-end server 30 includes a processor 32 and a memory 34 that stores non- transitory processor-executable instructions to perform one or more of the operations described herein. The back-end server 30 also includes a transceiver 36 configured to communicate with one or more devices, such as the mobile computing device 12, or a third- party server, via the communication network 24. The server 30 may communicate with mobile computing devices 12 via a suitable transport layer security protocol. In this way, any communication between the device 12 and the server 30 may be inherently encrypted and secure but may still be prone for hacking as will be understood by those skilled in the art.

The sever 30 may comprise a secured database 46 storing bank accounts, or associated data, for a plurality of users. In the system 10 as described herein, a user is permitted to access their bank accounts stored securely in the database 46, to perform any of the banking operations described herein, via their software application 18 on their mobile computing device 12, or via other devices such as their laptop computer or the like. For brevity, reference will only be made to a user accessing their bank accounts via the app 18.

The mobile computing device 12 and the server 30 operate in concert to permit a user to gain access to the secured data stored in the secured database 46 either via the software application on the mobile device 12 or via the website 42 accessible via the mobile computing device 12 or the laptop 44 over the communications network 24. In particular, the mobile device 12 and the server 30 operate to only provide access to the secured data stored in the secured database 46 upon identification, authentication, or verification of users based on their biometrics, for example, their fingerprints.

Reference to “fingerprints” herein may be actual fingerprints of a user, observable or visual images of a fingerprint which may be contained in a photograph, a fingerprint scan obtained by a conventional fingerprint scanner, or a conventional ink fingerprint of a user which corresponds to an actual fingerprint of a user, or actual fingerprints of the user. This may be depending on the context.

As alluded to above, there are drawbacks with conventional fingerprint scans, or the like being used for purposes of biometric identification, verification, or authentication. In this regard, in the system 10 described herein, the app 18 conveniently comprises a hasher 19 which is configured to hash fingerprint data associated with, representative of, or indicative of, the user's fingerprint, with a unique user password and an organisational salt using a cryptographically secure hashing function, such as a SHA-256 function, to generate a hashed template which may be: a) enrolled to the system 10 as an enrolled hashed template and associated with the user by way of a unique user identifier; and/or b) used as a probed hashed template to the system 10 to determine a match as described herein.

In this way, it is not conventional fingerprint minutia templates but hashed templates associated with users that are transmitted for one or more of enrolment, identification, verification, and authentication, for example, to give access to the user's bank account stored in the database 46. The system 10 serves to enhance security by removing or reducing threat of fingerprint minutia templates being intercepted during transmission for user identification, verification, or authentication. This is because, though undesirable, any transmitted hashed template which is intercepted may be meaningless, in themselves, to a cyber attacker or hacker whereas a fingerprint minutia template may be used to re- create a fingerprint of the user. Notwithstanding, the compromise of a single hash is still a serious problem, since the hash must be revoked and the user re-enrolled with a new password. The compromise of all the hashes of an organization is still a catastrophic event,

in that all hashes must be revoked, new salts chosen, and all users re-enrolled. What can be ensured however, is that the revoked compromised hashes cannot be replayed, and that provided the passwords are strong, any stolen hashes cannot be used to recover passwords nor useful fingerprint information.

The organisational salt may be specifically associated with an organisation, for example, the bank or system and may be part of the data which is downloaded with the app 18 and stored in the memory device 16. The salts are long random strings/byte-arrays, which once chosen, should never change, since changing salts requires full re-enrollment as hashes generated with different salts will never match.

It will be appreciated that the salts described herein are only used, and known, by the hasher 19, and are not known to hash matchers. The organizational salts are required at the point of hashing, which is often via a public device/API.

To use the system 10, a user must enrol their fingerprint/s to the system 10 for future identification, verification, or authentication. This is facilitated by the mobile computing device 12 by way of the software application 18 and is transmitted for one or more of identification, verification, and identification to the server 30 over the communications network as will be discussed below.

The server 30 typically comprises a database 38 which stores a plurality of enrolled hashed templates associated with enrolled users. The enrolled user is typically a human client of the bank or a human representative of a client of the bank that has been enrolled to use their fingerprint/s to access the secure database 46 in a manner described herein.

The enrolled hashed templates stored in the database 38 may be associated with unique user identifiers associated with the users. The unique user identifiers may be non- biometric identifiers and may be user selected or system generated usernames, a user's name and/or surname, a user's identification number or passport number, or any other deterministic additional user identifying data serving to identify the users, in addition to their fingerprints. The user identifiers may map the associated enrolled hashed templates to the associated secure user accounts stored in the secured database 46.

In some example embodiments, the databases 46 and 38 may be the same database, or may be segmented into multiple databases communicatively coupled, for example, across the network 24, storing data as described herein. Moreover, in some example embodiments, the hashed templated may be stored in the database 38 without any user identifiers, for example, a probed hashed template is compared with a plurality of stored hashed templates to determine a match.

The memory device 34 of the server 30 typically stores a software application comprising a hash matcher 35 which has processor-executable instructions which directs the operations of the processor 32 in a manner described herein to at least compare two hashed templates to determine a match. The processor 32 is configured to execute the processor-executable instructions stored in the memory device 34 corresponding to the hash matcher 35 and as such reference to operations of the hash matcher 35 may be understood to mean operations by the processor 32, or the collective server 30. Thus, the processes or methods ascribed to the hash matcher 35 may be interchangeably ascribed to the processor 32, and the server 30. Similarly, other method steps described herein may be ascribed to the server 30 though it may be the processor 32 operating under instruction of the processor-executable instructions to achieve the steps or processes described herein.

The processor 32 is communicatively coupled to the database 38 and is configured, under instruction of the hash matcher 35, to receive a probed hashed template; and compare the same with one or more enrolled hashed templates stored in the database 38 to determine a match, wherein the probed hashed template is a hash, with the suitable hashing function, of a probed user password, the salt, and fingerprint data associated with a fingerprint of a probed user.

Operation of the system 10 will be described in greater detail with reference to

Figures 2 to 5 of the drawings which illustrate flow diagrams of methods in accordance with an example embodiment of the invention. Though the methods illustrated and described are done so in relation to the system 10, it will be appreciate that the methods may be applied, mutatis mutandis, to other systems not illustrated or discussed herein. Moreover, it will be understood that variations not illustrated or discussed may be evident to those skilled in the art based on the disclosure herein and should not detract from teachings of the invention disclosed herein.

Referring to Figure 2 of the drawings where a flow diagram of a method in accordance with an example embodiment of the invention is generally indicated by reference numeral 50. The method 50 serves to enhance security of online interactions such as online banking transactions as discussed herein.

A user of an online banking service must first enrol themselves for subsequent matching before being able access or log in to their bank account stored in the secure server 46. In this regard, the user uses their app 18 on their mobile computing device 12 to perform the method steps described in Figure 2 to generate the hashed template for either enrolment or probing to gain access to their account.

In particular, the user may be prompted via the app 18 for various details ahead of in-app processing of these details in a manner described herein. In response to said prompting such as prompting the user for their user identifier, password and finger image, the method 50 comprises: receiving, at block 52, a user identifier, which may be a username or user identification number in the form of a character string, alphanumeric string, numeric string, or combination thereof of the user; receiving, at block 54, a user password, which may be a unique user selected password associated with the user in the form of a character string, alphanumeric string, numeric string, or combination thereof; and receiving, at block 56, a fingerprint minutia template associated with the user.

The fingerprint minutia template may be obtained from a conventional fingerprint scanner, or the like. In some example embodiments, the method 50 may comprise using standard fingerprint minutia template extraction techniques to obtain the fingerprint minutia template from a fingerprint scan.

The method 50 comprises processing the fingerprint minutia template, at block 62 with the hasher 19, to determine the fingerprint data, by determining classes of at least pairs of minutiae in the minutia template, wherein the classes partition the minutia template based on one or more attributes of the minutiae, or the pairs of minutiae, which are rotationally and translationally invariant, and wherein the fingerprint data is representative of the determined classes.

The method comprises hashing, at block 64 also with the hasher 19, the determined fingerprint data, the received user password, and a salt which is specific to the organisation, which in this case is a bank, with a cryptographically secure hashing function to generate the hashed template.

The system 10 described herein is partially vulnerable to the common password attack, in the sense that if the attacker has access to the entire enrolled hashed template database 38, they can recognize which templates derive from the same password. While the hashed templates reveal little or no useful information in such cases, a common password is typically a weak password, thus suggesting to the attacker which hashes are best for a weak password attack.

In this regard, the method 50 may comprise concatenating additional fixed user specific information, such as the user identifier, to the actual user password, to generate a stronger user password; and using the stronger user password as the actual password passed to the hasher 19. This rules out (if the additional information is the user identifier or user identifying information) or reduces (if the additional information is not the user identifier or user identifying information) the possibility of identifying hashed templates with the same password. Inthe case of verification, the user identifier can be appended or concatenated.

In the case of identification, however, this is not possible.

The example embodiment referred to above may be exemplified with reference to

Figure 3 of the drawings which expands on the method steps 62 and 64, and operation of the hasher 19 in accordance with an example embodiment of the invention.

The method 50 comprises using the generated hashed template to do one or more of enrolling the user to the system 10, determining an identify of the user, verifying the identity of the user, or authenticating the identity of the user based on their fingerprint or generated hashed template. To this end, the method 50 comprises transmitting, at block 686, the hashed template as well as the user identifier from the mobile computing device 12 of the user for the purposes of enrolment, identification, verification, or authentication of the user. The hashed template is transmitted to the server 30 over the network 24 in an encrypted format.

It will be appreciated that it is optional to also send the user identifier to the server 30, the only reason being the speed of identification versus verification. In the verification model, the server 30 or the hash matcher 35 looks up the enrolled hashed template and compares it against the probe. In the identification model, the probe is matched against all the enrolled hashes, and if a match is found, the associated user is identified.

As alluded to above, the method 50 is discussed with reference to the same being carried out by the app 18 operating on the mobile computing device 12. However, it will be understood that in some example embodiments, the app 18 , or components thereof, such as the hasher 19, may be software application/s stored or provided in the memory device 34 of the server 30. In some example embodiments, the app 18 merely prompts users for information which it receives and transmits to the server 30 for further processing in the manner described herein. For example, the app 18 may prompt the user for their user identifier in the form of their username, password, and a scan of their finger or a minutia template which they merely transmit to the at least one processor 32 for processing in the manner discussed herein. These example embodiments may be less secure as sensitive data such as user passwords and fingerprint data or images are being transmitted and may be vulnerable for interception but are within the scope of the disclosure for completeness.

Turning to Figure 3 of the drawings, wherein a flow diagram of a method in accordance with an example embodiment of the invention is generally indicated by reference numeral 60.

The method 60 expands on the method steps 62 and 64 as described above with reference to Figure 2 and as such may be regarded as a method of hashing a fingerprint minutia template.

In this regard, the method 60 comprises processing, at block 61 by way of the hasher 19, the received fingerprint minutia template to extract or determine a set comprising a plurality of positionally distinct n-tuples of minutiae of fixed size from the received fingerprint minutia template. In a preferred example embodiment, the n-tuple is a minutia pair comprising a first minutia and a second minutia.

For each minutia pair in the selected set, the method 60 may comprise determining, at block 83, a unique class identifier or index (UCI) of the minutia pair. The UCI or is associated with one of a predetermined number of equivalence classes, based on attributes of the minutia pair, or minutiae of the minutia pair, which are rotationally and translationally invariant. In this regard, it will be noted that the UCI for each minutia pair in the template may be rotationally and translationally invariant. As described above, this may comprise allocating a minutia pair to a particular equivalence class, wherein membership is based on the attributes of the minutia pair, particularly the attributes of the distance between the minutiae of the minutia pair, the first and second relatively angle orientations, and a type of the first and second minutiae of the minutia pair.

The method 60 may conveniently comprise partitioning the set into a plurality of partitions. In particular, a distance partition, and angle partition which are labelled or indexed partitions which are labelled or indexed by suitable identifiers in the manner described herein.

In particular, the method 60 comprises determining a distance between minutiae of the minutia pair, determining a unique distance identifier or index (UDI) of the at least one minutia pair, wherein the UDI is an identifier of the sub-interval of the distance partition containing the determined distance. The method 60 further comprises determining a first relative orientation angle of the first minutia of the minutiae pair; determining a second relative orientation angle of the second minutia of the minutiae pair; and determining a first unique angle identifier or index (UAI) of the minutia pair, wherein the first UAI is an identifier of the sub-interval of the angle partition, determined by the determined UDI and the map, containing the determined first relative orientation angle of the first minutia of the at least one minutiae pair, and determining a second UAI in a similar fashion for the second minutia.

The method 60 also comprises determining a first type of identifying data associated with first minutia of the minutia pair, from at least two different identifying data types; and determining a second type of identifying data associated with the second minutia of the minutia pair, from the at least two different identifying data types.

The method 60 may comprise determining the UCI i for the minutia pair is based on the determined UDI, the first and second UAI, the first type of identifying data, and the second type of identifying data by way of the following equation: wherein index io: is the index of the sub-interval containing the first relative orientation 0%}, in an indexed angle partition Oli} where each Plilis a partition of angles into contiguous subintervals, calling © the relative orientation partitions; iz is the index of the subinterval containing the second relative orientation rox{filin the angle partition Ol). iy is the first type index which his defined to C if the first minutiae of the pair is a bifurcation, and 1 otherwise; and i is the second type index which is defined to 0 if the second minutiae of the pair is a bifurcation, and 1 otherwise. N is typically the maximum number of sub-intervals of any Olid},

In any event, the method 60 may comprise combining by concatenating, at block 65, the determined UCI, the user password, and a salt into a combined dataset. As mentioned, alluded to above, the method 60 may also comprise concatenating the user identifier as well prior to hashing.

The method 60 then comprises hashing, at block 67, the combined dataset with a hash function to obtain a unit-digest.

Lastly, the method 60 comprises collecting, at block 69, the unit-digests into a 16 hashed template which may be used for one or more of enrolment, or matching for purposes of one or more of identification, authentication, and verification of the user.

In some example, embodiments, the method 60 may comprise using the generated hashed template, or the unit-digests, to derive further hashed templates as described herein, such as the compact, sharp, labelled, or absolute hashed template as described herein which may be used for one or more of enrolment, or matching for purposes of one or more of identification, authentication, and verification of the user. It will be appreciated that the derived hashed templates may increase the EER of matching.

Reference is now made to Figure 4 of the drawings wherein a flow diagram of a method of enrolling a user, particularly their hashed fingerprint template in the database 38 is generally indicated by reference numeral 70. The method 70 is typically performed by the server 30 in communication with the mobile computing device 12.

A user to be registered or enrolled to use the system 10, for example, to access their bank accounts in the database 46, proceeds with commencing enrolling themselves by way of their mobile computing device 12. In particular, the method 50 is followed and the generated hashed template is transmitted wirelessly over the network 24 to the server 30.

The method 70 comprises receiving, at block 72 at the server 30, the generated hashed template to be enrolled from the mobile computing device 12 of the user, and receiving, at block 74, the user identifier. As mentioned, the user identifier may be optional in some example embodiment implementations.

The method 70 comprises storing, at block 76, the received hashed template as an enrolled template in the database 38 and, associating, at block 78, the enrolled template with the user identifier. In some example embodiments, the user identifier may map the enrolled template with the associated bank account of the user stored in the database 46.

It will be appreciated that the hashed templates are only as strong as their deter- mining password and thus the app 18 must prompt the user for a strong password and/or present one to the user. With knowledge of the parameters, the salts and the password, it is feasible to recover the determining minutia template. This may be true for all biometric key-binding systems, and hence why secure password-less biometric hashing is impossible.

If an attacker has access to a matching score of standard fingerprint matching systems, then this can be exploited to reveal the enrolled fingerprints, through techniques such as hill-climbing. Even if the matching score is hidden, and only a yes/no interface is available, this too may be exploited, due to the low EER of fingerprint matching systems, which are currently at levels between 0.05 to 0.001. The attacker begins by iterating through a few hundred (to a few thousand) random fingerprints (from available fingerprint databases) and, due to the low EER, will soon find a match. While this matching fingerprint is not the real fingerprint, it will certainly pass as such. Further, the attacker can remove minutiae and retest, until they find a minimal sets that matches. By dropping a single minutia from a minimal set, the attacker can then find more real minutiae, by iterating over a single minutia and adding it to the set until a match occurs again. The attacker can eventually recover the real fingerprint.

In a scenario in which an attacker knows the salt, and has a pure hashed template (no password), or a key-bound hashed template with knowledge of the key. The hash matcher presents as that of a standard {non-hashed) fingerprint matcher, providing either an increasing matching score in all currently existing hash matchers, or possible just a yes/no interface (al- though no existing hash-matchers exist). Either way, as “standard” fingerprint matchers, they must be vulnerable to the two attacks described above.

Reference is now made to Figure 5 of the drawings wherein a flow diagram of a method of matching a fingerprint hash or hashed fingerprint template is generally indicated by reference numeral 80. The method 80 is typically performed by the server 30 in communication with the mobile computing device 12.

As alluded to above, a user wanting to be, or requiring to be, identified, verified, or authenticated, for example, to access their bank account stored in the database 46 must first generate a hashed template by way of their mobile computing device 12 as discussed herein with reference to Figure 2. In particular, the method 50 is followed and the generated hashed template to be probed is transmitted wirelessly from the mobile computing device 12 to the server 30, over the network 24.

The method 80 comprises receiving, at block 82 at the server 30, the generated probed hashed template to be compared with one or more enrolled hashed templates stored in the database 38; and the receiving, at block 84, the user identifier.

The method comprises retrieving the enrolled hashed template associated with, or corresponding to, the user identifier stored in the database 38; and comparing, at block 86, the enrolled hashed template with probed hashed templated to determine a match by way of the hash matcher 35.

If a match is determined, at block 88, the method 80 comprises permitting the user access to their bank account. However, if a match is not determined, at block 88, the method 80 comprises generating and/or transmitting a suitable failure message to the user via the app 18 which may prompt the user to re-generate and re-transmit a hashed template for probing.

It will be understood by those skilled in the art that determining a match may comprise determining, by way of the hash matcher 35, whether there is correlation between the received hashed templated and that of the enrolled hashed template which falls within a predetermined tolerance range.

In particular, the input to the hash matcher 35 is two hashes, a probed and an enrolled hashed template, and the output is a non-negative matching score, where 0 means no match, while the higher the score the better the match. If the two hashes were generated with different passwords or salts, then the matching score will be 0 with cryptographically high probability, otherwise, the matching score behaves like a Bozorth3 based match of the determining minutiae templates.

Referring to Figure 6 of the drawings, an example of a mobile computing device 100 is shown. The mobile computing device 100 may be configured to perform one or more of the functions and methods described above with reference to Figures 1 to 5 of the drawings.

In one example embodiment, the mobile device 100 may include or correspond to the mobile device 12 of Figure 1 as described herein.

The device 100 includes a computer-readable storage device 106, one or more processors 108 (e.g., a central processing unit (CPU), a digital signal processor (DSP), a graphics processing unit (GPU), etc.) and a memory device or memory 110. The storage device 106 may be implemented as read-only memory (ROM), random access memory (RAM), and/or persistent storage, such as a hard disk drive, a flash memory device, or other type of storage device. The memory 110 is non-transitory computer readable medium configured to store instructions 112 which are executable by the processor 108 to perform one or more of the functions or methods described above with reference to Figures 1 to 5.

In this regard, the memory 110 may be configured to store the software application 18 of

Figure 1 and may perform one or more of the functions or methods described above with reference to Figures 1 to 5. The computer-readable storage device 106 is not transitory or a signal.

The mobile device 100 also includes a location device 116 (e.g., a GPS transceiver) and one or more wireless transceivers 114 that enable the mobile device 102 to exchange signals with (e.g., receive signals from and/or send signals to) other devices. Each wireless transceiver 114 may include or be coupled to radio frequency (RF) circuitry 117, a controller 118, and/or an antenna 119. In illustrative examples, the wireless transceivers 114 include a third generation (3G) transceiver, a fourth generation (4G) transceiver, a Wi-Fi ® transceiver, a near field communication (NFC) transceiver, a BLUETOOTH® or

BLUETOOTH® low energy (BLE) transceiver, or any combination thereof.

The mobile device 100 is configured to utilize one or more of the wireless transceivers 114 for direct peer-to-peer communication and communication via one or more networks 124, such as the internet. The mobile device 100 may communicate with external device (e.g., an automated teller machine (ATM) for contact-less ATM authentication) via a peer-to-peer wireless channel (e.g., BLUETOOTH, BLE, or NFC).

In the example of Figure 6, the mobile device 100 includes or is coupled to input devices and output devices. For example, the mobile device 100 may include or may be coupled to a display device 132, a microphone 134, a speaker 136, and/or a user input device 138 (e.g., a touchscreen). It should be noted that, while illustrated as outside of the mobile device 100, one or more of the devices 132-138 may be integrated into a housing of the mobile device 100, such as in the case of a mobile phone or tablet computer.

Referring to Figure 7 of the drawings, an illustrative example of a server 200 is shown. The server 200 may be configured to perform one or more of the functions and methods described above with reference to Figures 1to 5. In a particular implementation, the server 200 includes or corresponds to the back-end server 30 of Figure 1.

The server 200 includes a computer-readable storage device 208, one or more processors 208 (e.g., a central processing unit (CPU), a digital signal processor (DSP), a graphics processing unit (GPU), etc.) and a memory 210. The storage device 206 may be implemented as read-only memory (ROM), random access memory (RAM), and/or persistent storage, such as a hard disk drive, a flash memory device, or other type of storage device. The memory 210 is configured to store instructions 212 executable by the processor 208 to perform one or more of the functions or methods described above with reference to Figures 1 to 5. The computer-readable storage device 206 is not a signal.

The server 200 also includes one or more transceivers 214 that enable the server 200 to exchange signals with (e.g., receive signals from and/or send signals to) other devices. In some implementations, the transceivers 214 are wireless transceivers, and each transceiver 214 may include or be coupled to radio frequency (RF) circuitry, a controller, and/or an antenna. In illustrative examples, the transceivers 214 include a third generation (3G) transceiver, a fourth generation (4G) transceiver, a Wi-Fi® transceiver, a near field communication (NFC) transceiver, a BLUETOOTH® or BLUETOOTH® low energy (BLE) transceiver, a wired transceiver, or any combination thereof. In the example of Figure 6, the server 200 is configured to utilize one or more of the transceivers 214 for communication via one or more networks 24, such as the internet. To illustrate, the server 200 may communicate with mobile device 100 via the internet.

The server 200 optionally includes a location device 216 (e.g., a GPS transceiver).

In the example of Figure 6, the server 200 also optionally includes or is coupled to input devices and output devices. For example, the server 200 may optionally include or may be coupled to a display device 232, a microphone 234, a speaker 236, a user input device 238 (e.q., a touchscreen), or a combination thereof.

The systems and methods disclosed herein provides a convenient way to enhance security of biometric systems, for example, banking systems in a manner which does not transmit or store user passwords or user fingerprints.

Claims

CONCLUSIONS

1. A processor-implemented method for hashing a minutia template of a fingerprint, the method comprising: receiving a minutia template of a fingerprint comprising a plurality of fingerprint minutia; receiving a user password; determining a plurality of positionally distinguishable n-tuples of fixed-sized minutiae from the received minutia template of a fingerprint, each n-tuple comprising at least one minutia pair; and wherein for each n-tuple in the determined plurality of positionally distinguishable n-tuples, the method comprises: determining a unique class identifier (UCI) of the n-tuple, the UCI being associated with one of a determined number of equivalence classes, based on attributes of the n-tuple, or minutiae of the n-tuple, that are rotationally and translationally invariant; combining the determined UCI, the user password, and a salt into a combined data set; and hashing the combined dataset with a hash function to obtain a hash value of the unit.

2. A processor-implemented method as claimed in claim 1, wherein the method comprises collecting the hash value of the unit into a hashed template.

3. A processor-implemented method as claimed in claim 1 or claim 2, wherein determining the UCI for each n-tuple is based on attributes of the n-tuple selected from a group comprising a type or types of each minutia of the n-tuple, a distance or distances between each minutia of the n-tuple, and a relative orientation or relative orientations of minutia of the n-tuple.

4. A processor-implemented method according to any preceding claim, the method comprising: providing a distance partition having a plurality of distance sub-intervals, each sub-interval being associated with a unique distance identifier (UDI);

providing an angle partition having a plurality of angle subintervals, each angle subinterval being associated with a unique angle identifier (UAL), and wherein determining the UCI of each n-tuple is based on a type or types of minutia in the n-tuple, a UDI of the at least one minutia pair in the n-tuple, and UAl's of the relative orientations of the at least one minutia pair in the n-tuple.

5. The processor-implemented method of claim 4, the method comprising: providing a map of UDIs to a plurality of corner partitions and, each corner partition having a plurality of corner sub-intervals, and each corner sub-interval being associated with the unique corner identifier (UAI); and wherein determining the UCI is based on the types of minutia in the n-tuple, the UDI of the at least one minutia pair, and/or the UAI of relative orientations of the at least one minutia pair in the corner partition determined by the UDI of the at least one minutia pair in the map.

6. The processor-implemented method of claim 5, wherein determining the UCI for each n-tuple of the plurality of positionally distinguishable n-tuples comprises: determining a distance between minutiae of the at least one minutia pair; determining a UDI of the at least one minutia pair, the UDI being an identifier of the sub-interval of the distance partition containing the determined distance; determining a first relative orientation angle of the at least one minutia pair; determining a second relative orientation angle of the at least one minutia pair; determining a first UAI of the at least one minutia pair, the first UAI being an identifier of the sub-interval of the angle partition defined by the determined UDI and the map containing the determined first relative orientation angle of the minutiae of the first minutia pair;

determining a second UAI of the at least one minutia pair, the second UAI being an identifier of the sub-interval of the angular partition determined by the determined UDI and the map, containing a determined second relative orientation angle of the minutiae of the at least one minutiae pair; determining a first type of identification data associated with one minutia of the at least one minutia pair, of at least two different identification data types; and determining a second type of identification data associated with another minutia of the at least one minutia pair, of the at least two different identification data types; wherein determining the UCI is based on the determined UDI, the first and second UAI, the first type of identification data and/or the second type of identification data.

7. A processor-implemented method as claimed in claim 6, wherein for n-tuples having a plurality of minutiae, the method comprises performing the method for each successively different minutia pair in the n-tuple.

8. The processor-implemented method of claim 6 or claim 7, wherein for each n-tuple, the method comprises: determining a residual distance hash, by: determining a residual distance associated with the at least one minutia pair; combining the determined UDI, the user password, and a residual distance salt into a combined residual distance data set; hashing the residual distance data set with a hash function to obtain a distance hash; applying a hash transformation to the distance hash, the hash transformation mapping the distance hash to a real number; and adding the determined residual distance to the hash transformation of the distance hash, and rounding the resulting sum to a first determined number of decimal places to yield the relative distance hash; determining a residual orientation hash by: determining a first relative residual orientation associated with the at least one minutia pair;

combining the determined UDI, the user password, and a first relative restoration orientation salt into a combined first relative restoration orientation data set; hashing the first restoration orientation data set with a hash function to obtain a first relative orientation hash; applying a hash transformation to the first relative orientation hash, the hash transformation mapping the first relative orientation hash to a real number; and adding the determined first relative remainder orientation to the hash transformation of the first relative orientation hash and rounding the resulting sum to a second determined number of decimal places to yield the first relative remainder orientation hash; determining a second relative remainder orientation hash, by: determining a second relative remainder orientation associated with the at least one minutia pair; combining the determined UDI, the user password, and a second relative remainder orientation salt into a combined second relative remainder orientation data set; hashing the second relative residual orientation data set with a hash function to obtain a second relative orientation hash; applying a hash transformation to the second relative orientation hash, the hash transformation mapping a range of the second relative orientation hash to a real number; and adding the determined second relative residual orientation to the hash transformation of the second relative orientation hash, and rounding the resulting sum to the second determined number of decimal places to obtain a second relative residual orientation hash; and generating a unit hash comprising the hash value of the unit, the residual distance hash of the at least one minutia pair, the first relative residual orientation hash of the at least one minutia pair, and the second relative residual orientation hash of the at least one minutia pair.

9. The processor-implemented method of claim 8, the method comprising: determining the residual distance by determining a difference between the determined distance of the at least one minutia pair and a lower bound of a sub-interval of the distance partition containing the determined distance; determining the first relative residual orientation angle by determining a distance between the first relative orientation angle of the at least one minutia pair and a lower bound of the sub-interval of the angle partition containing the first relative orientation angle; determining the second relative residual orientation angle by determining a distance between the second relative orientation angle of the at least one minutia pair and a lower bound of the sub-interval of the angle partition containing the second relative orientation angle; and generating a sharpened unit hash comprising the hash value of the unitn, the residual distance hash, the first relative residual orientation hash, and the second relative residual orientation hash.

10. The processor-implemented method of claim 9, wherein the method comprises collecting the generated sharpened unit hashes into a sharpened hash template.

11. The processor-implemented method of claim 8, the method comprising: determining the residual distance by: providing a compactification value based on the determined UDI; determining a compactification factor by determining a sum of the determined distance between the minutiae of the at least one minutia pair and a product of the determined compactification factor and a difference between a midpoint of the sub-interval of the distance partition containing the determined distance and the determined distance; and determining the residual distance by determining a difference between the determined compactification value and the lower bound of the sub-interval of the distance partition containing the compactification value;

determining the first relative residual angle orientation by: providing a first relative orientation compactification factor based on the determined first UAI; determining a first relative orientation compactification value by determining a sum of the determined first relative orientation value, and a product of the determined first relative orientation compactification value and a difference between a midpoint of the sub-interval of an angle partition containing the determined first relative orientation angle and the determined first relative orientation value; and determining the first relative residual angle orientation by determining a difference between the determined first relative orientation compactification value and the lower limit of the sub-interval of the angle partition containing the first relative orientation compactification value; and determining the second relative residual angle orientation by: providing a second relative orientation compactification factor based on the determined second UAI; determining a second relative orientation compactification value by determining a sum of the determined second relative orientation value, and a product of the determined second relative orientation compactification value and a difference between a midpoint of the sub-interval of the angular partition containing the determined second relative orientation angle and the determined second relative orientation value; and determining the second relative residual angle orientation by determining a difference between the determined second relative orientation compactification value and the lower bound of the sub-interval of the angular partition containing the second relative orientation compactification value; and generating a compact unit hash comprising the unit hash value, the residual distance hash, the first relative residual orientation hash, and the second relative residual orientation hash.

12. The processor-implemented method of claim 11, wherein the method comprises collecting the generated compact unit hashes into a compact hashed template.

13. The processor-implemented method of claim 8, wherein, for each n-tuple, the method comprises: providing a label for each minutia of the minutia template; and combining the unit hash with the n-tuple of labels for each minutia of the minutia n-tuple.

14. The processor-implemented method of claim 8, the method comprising: determining a translation property to be added to each sharpened unit hash, the translation property being a point having an x component and a y component, by: providing a translation determination function; deterministically mapping the n-tuple to an absolute point using the translation determination function provided, the absolute point having an absolute x component and an absolute y component; combining the UCI, the user password, and an organizational salt into a combined mapped x component data set; hashing the mapped x component data set with a hash function to obtain a hash of the mapped x component; performing a hash transformation on the x component mapped hash to obtain an x transformation; adding the absolute x component to the x transformation, and rounding the resulting sum to a first specified number of decimal places to yield the x component of the translation property; combining the UCI, user password, and organizational salt into a combined mapped y component dataset; hashing the mapped y component dataset with a hash function to obtain a hash of the mapped y component;

performing a hash transformation on the y component mapped hash to obtain a y transformation; and adding the absolute y component to the vy transformation, and rounding the resulting sum to the first specified number of decimal places to yield the y component of the translation property; determining a rotation property to be added to the sharpened unit hash by: providing a rotation determination function; deterministically mapping the n-tuple to an absolute angle with the provided rotation determination function; combining the UCI, the user password, and a third global salt into a combined angle mapped data set; hashing the angle mapped data set with a hash function to obtain a hash value of the angle mapped; and applying a hash transformation to the angle mapped hash value; adding the absolute angle to the hash transform of the hash value of the mapped angle; and converting the resulting sum to a form of 0° to 360° and rounding the converted resulting sum to a first specified number of decimal places to obtain the rotation property to be added to the unit hash; and combining the unit hash, the translation property, and the rotation property into an absolute unit hash.

15. The processor-implemented method of claim 13, wherein the method comprises collecting the absolute unit hashes into an absolute hashed template.

16. A processor-implemented method according to any preceding claim, the method comprising receiving user-specific data associated with the user and combining the user-specific data with the received password prior to hashing.

17. A processor-implemented method as claimed in any of claims 2, 10, 12 or 15, the method comprising transferring the hashed template to a remote server.

18. A processor-implemented method for matching hashed templates, the method comprising: receiving a hashed template according to any of claims 2, 10, 12 or 15; comparing the received hashed template with one or more hashed templates stored in a database; and determining a match between the received hashed template and a stored hashed template based on a measure of the hash value of the unit of the received hashed template corresponding to the hash value of the unit of the stored hashed template.

19. A system comprising: at least one processor; and a memory device coupled to the at least one processor, the memory device storing non-volatile processor-executable instructions that, when executed on the at least one processor, cause the at least one processor to perform the method of any one of claims 1 to 18.

20. A non-volatile processor-executable storage medium storing processor-executable instructions which, when executed on at least one processor, cause the at least one processor to perform the method of any one of claims 1 to 18.