RU2726930C1 - Cryptographic recursive 2-d integrity monitoring method of electronic documents files metadata - Google Patents

Abstract

FIELD: computer equipment.SUBSTANCE: invention relates to computer engineering. In method when performing operation of recording and editing electronic documents files at time t, t, …, tin memory of data processing system rows and columns are formed, containing metadata records, over which cryptographic transformation operations are performed on subsets of switchesas a result of which signature values of corresponding columns and rows are formed, above which concatenation operations with subsequent records are performed, after which these operations are performed similarly for all rows and columns. All records and corresponding signatures are stored in memory of data processing system in form of data table.EFFECT: high level of security of metadata of electronic document files with possibility of monitoring their integrity, detection and localization of unauthorized modified records caused by deliberate actions of authorized users (insiders).3 cl, 4 dwg

Description

The technical field to which the invention relates

The proposed invention relates to the field of ensuring the security of information processed in automated information systems (AIS), namely to methods of monitoring the integrity of metadata files of electronic documents, and can be used in electronic document management systems, in order to control and ensure the integrity of the processed data, in conditions deliberate influence of authorized users (insiders).

State of the art

Currently, users of various AIS are faced with the task of ensuring the security of information circulating in them. Such information includes files of electronic documents, which are managed on the basis of a special type of information resources - metadata. The term "metadata" refers to data describing the context, content and structure of documents, as well as the processes of their management throughout the entire life cycle of a document (GOST R ISO 15489-1-2007. System of standards for information, library and publishing. Document management) ... They are critical to ensure the value, safety and manageability of electronic documents files, which necessitates the development of mechanisms to protect them from the destructive influences of an attacker. The result of such influences can be a deliberate unauthorized change of metadata, which will lead to a violation of their integrity, and, as a consequence, loss of control over the files of electronic documents processed by AIS. One of the measures to ensure the security of data is to protect their integrity (Methodological document. Measures for protecting information in state information systems: approved by the Director of FSTEC 11.02.2014 // FSTEC of Russia, 2014. - 176 p.).

Typically, the task of protecting data integrity is solved using various methods. Further, to disclose the essence of the invention, a brief description of existing technical solutions for data integrity control is given.

a) Description of analogs

1. “Validating computer program installation)) according to US patent 20030192033, 2002, [Electronic resource] - https://books.google.com.tr/patents/US 20030192033.

2. Software complex "Shield System Manager Integrity Control System"), [Electronic resource] - http://lissiru.narod.ru/products/index.html.

3. Hardware and software complex of trusted download "Blockhost-MDZ" [Electronic resource] - https://gaz-is.ru/poddergka/download/finish/6/8.html.

In these solutions, to control the integrity of information, a hash function is used (a function that maps strings of bits of the original data to strings of bits of a fixed length - a hash code).

The disadvantage of such solutions is the low level of protection of data records from attacks from authorized users (insiders). When maintaining successive data records in the file (records in the electronic medical history, the security audit event log), the user (or one of the administrators), having his own key (when using key hash functions), has the ability to change (fake) his records stored in file earlier. That is, these solutions do not take into account internal data security threats from legal users (insiders).

A known method for monitoring the integrity of data records based on the "write once" method (Atsushi Harada, Masakatsu Nishigaki, Masakazu Soga, Akio Takubo, Itsukazu Nakamura. A Write-Once Data Management System, ICITA 2002. - Shizuoka University, Japan, 2002, [Electronic resource] - http://www.icita.org/previous/icita2002/ICITA2002/kptdata/116-21/index.htm), which uses various combinations of user electronic signatures to protect (integrity control) records from authorized users.

The disadvantage of this solution is the lack of functionality to establish additional parameters for entering key data of various users and the order of their use (secret for the users themselves or for various groups of users, the composition of which is not known to the users themselves), allowing to ensure the appropriate level of security of data records in the file.

A well-known method of authenticating HMAS messages (hash-based message authentication), the essence of which is to use a cryptographic hash function in combination with one secret key and NMAC with two secret keys (M. Bellare, R. Canetti and N. Krawczyk, Keying Hash Functions for Message Authentication, Advances in Cryptology Proceedings of CRYPTO 1996, pp. 1-15, Springer-Verlag, [Electronic resource] - http://dblp.uni-trier.de/db/conf/crypto/crypto96, [Electronic resource] - http://daily.sec.ru/2012/07/16/print-Algoritmi-auntentifikatsii-soobsheniy-HMAC-i-NMAC.html).

где

- символ конкатенации, hash - функция вычислений в блоке формирования хэш-кода. Сообщение с кодом аутентичности (М, N) по каналу передачи сообщения, расположенного в недоверительной среде, поступает получателю.The control of message integrity in the NMAC message authentication method is that the sender of the message M using two secret (foreign) keys k ₁ and k ₂ calculates the message authenticity code according to the rule:

Where

- concatenation symbol, hash - calculation function in the hash-code generation unit. A message with an authenticity code (M, N) arrives at the recipient via a message transmission channel located in an untrusted environment.

The relying party (the recipient of the message) checks the compliance of the received authentication code H * to control the integrity and authentication of the message M *.

The disadvantage of this method is the low level of data protection against attacks from authorized users (insiders) (it is necessary to have two parties trusting each other, confidentiality of secret keys).

b) Description of the closest analogue (prototype)

The closest in technical essence to the claimed invention (prototype) is the "System for monitoring the integrity of logs of continuously conducted data records" according to RF patent No. 2015152423, which allows monitoring the integrity of the logs of continuously being recorded data. An essential feature that distinguishes the prototype from known analogues is that both keyless and key hash functions are used to control the integrity of data processed in AIS, which are used to ensure the required level of data security.

The disadvantages of the prototype are:

1. The inability to localize the numbers of data records with signs of violation of integrity, when implementing destructive actions by authorized users on the AIS.

2. The relatively high complexity of the operation to control the integrity of data records, since its implementation requires the use of the entire set of keys K _U at all stages of data transformation, which

represents a significant limitation and technical difficulty for using this method, especially in mobile applications.

Disclosure of the invention (its essence)

a) the technical result to which the invention is aimed

The aim of the claimed invention is to increase the level of security of the metadata of electronic document files processed by AIS, with the ability to control their integrity, as well as to detect and localize numbers of unauthorized modified metadata records, in case of violation of their integrity by authorized users (insiders).

b) a set of essential features

над различными записями z_j1,zj₂,…,z_ji. метаданных и значениями Р_(j-1)1, P_(j-1)2,…, P_(j-1)i сигнатур, вычисленных на предыдущем этапе итерации. Полученные результаты сохраняются в памяти системы обработки данных для последующего контроля целостности потока метаданных.This goal is achieved by the fact that in the well-known technical solution, the integrity of metadata when recording and editing files of electronic documents is controlled due to the fact that records z _j1 , zj ₂ , ..., z _{ji of} metadata are formed, cryptographic transformations of records z _j1 , zj ₂ ,…, Z _{ji of} metadata using the set of keys K _U. Then binary concatenation operations are performed

over different records z _j1 , zj ₂ ,…, z _ji . metadata and values P _{(j-1) 1} , P _{(j-1) 2} , ..., P _{(j-1) i} signatures calculated in the previous iteration step. The results obtained are stored in the memory of the data processing system for subsequent control of the integrity of the metadata stream.

и

при этом каждые подмножества

и

где q=1,…,3, для всех

При выполнении операции записи и редактирования файлов электронных документов в моменты времени t₁,t₂,…,t_k в памяти системы обработки данных формируются строки:A comparative analysis of the claimed solution with the prototype shows that the proposed method differs from the known one in that the set of keys K _{U is} divided into two subsets

and

moreover, each subsets

and

where q = 1, ..., 3, for all

When performing the operation of recording and editing electronic document files at times t ₁ , t ₂ , ..., t _k , the following lines are formed in the memory of the data processing system:

m (t ₁ ) = [z ₁₁ … z _1i ], m (t ₂ ) = [z ₂₁ … z _2i ],…, m (t _k ) = [z _kl … z _ki ],

containing metadata records z _j1 , z _j2 ,…, z _ji for all j = 1,…, k and columns:

Cryptographic transformation operations are performed over the metadata records z ₁₁ , ..., z _1i in the corresponding columns at time t ₁ :

на ключах

on keys

as a result of which the values of signatures P ₁₁ , ..., P _{1i are formed} .

Further, over each pair of the obtained signature values P ₁₁ , ..., P _1i and metadata records z ₂₁ , ..., z _2i , changed at the time t ₂ , the concatenation operation is performed:

over the results of which cryptographic transformation operations are performed:

After that, operations on metadata records are performed in a similar order within each column:

in accordance with the times t ₃ , t ₄ , ..., t _k .

In this case, in the line m (t ₁ ) = [z ₁₁ ... z _1i ], at time t ₁ , operations of cryptographic transformation of all records z ₁₁ , ..., z _1i , metadata of the line are performed:

на ключах

on keys

на ключах

on keys

и

соответственно.resulting in signature values

and

respectively.

After that, over the received signatures and subsequent records z ₂₁ , ..., z _2i . metadata of the string m (t ₂ ) = [z ₂₁ ... z _2i ], changed at time t ₂ , concatenation operations are performed:

over the results of which a cryptographic transformation operation is performed:

на ключах

on keys

на ключах

on keys

As new metadata records arrive, the operations are repeated in a similar order in accordance with the times t ₃ , t ₄ , ..., t _k .

All metadata records:

[z ₁₁ ,…, z _1i ],…, [z _k1 ,…, z _ki ]

and the corresponding signatures:

are stored in the memory of the data processing system in the form of a data table.

Metadata integrity control is carried out on the basis of signature data extraction from the table:

and records:

результатом которых является вычисление сигнатур:passed the storage procedure and subject to integrity control. Then, repeated cryptographic transform operations are performed on the extracted records

the result of which is the calculation of signatures:

Next, the received signatures are compared in pairs with the previously saved signatures:

The conclusion about the absence of violation of the integrity of signatures is made when fulfilling the equalities:

где q=1,…,3; j=1,…,k,

where q = 1, ..., 3; j = 1,…, k,

otherwise, it is concluded that the integrity of the corresponding signature numbers has been violated.

может являться ключевой хэш-функцией, где как на этапе подготовки, так и на этапе контроля целостности записей метаданных выполняется равенство

где q=1,…,3, для всех

In this case, the cryptographic transformation operation

can be a key hash function, where both at the stage of preparation and at the stage of controlling the integrity of metadata records, equality

where q = 1, ..., 3, for all

может являться электронной цифровой подписью, включающей в себя последовательно выполняемые преобразования бесключевой хэш-функции и функцию ассиметричного криптографического преобразования, при этом

то есть на этапе подготовки записей метаданных файлов электронных документов используется подмножество ключей

а на этапе контроля целостности записей метаданных используется подмножество ключей

Also, the cryptographic transformation operation

can be an electronic digital signature, which includes sequentially performed transformations of a keyless hash function and an asymmetric cryptographic transformation function, while

that is, at the stage of preparing metadata records of electronic documents files, a subset of keys is used

and at the stage of integrity control of metadata records, a subset of keys is used

c) the causal relationship between the features and the technical result Thanks to the new set of essential features, the method has the ability to:

providing cryptographic recursive two-dimensional control of the integrity of the metadata of electronic documents files;

reducing the likelihood of collusion between trusted parties, by ensuring mutual control over the actions of authorized users (insiders) of the AIS;

localization of numbers of modified metadata records, in the conditions of deliberate influence of authorized users (insiders).

Thus, the proposed technical solution allows you to ensure the required level of security of metadata records of electronic documents files processed in AIS.

The performed analysis of the prior art made it possible to establish that analogs characterized by a set of features that are identical to all features of the claimed method are absent, which indicates the compliance of the claimed method with the "novelty" condition of patentability.

The search results for known solutions in this and related fields of technology in order to identify features that match the distinctive features of the prototype features of the claimed method, showed that they do not follow explicitly from the prior art. The prior art also did not reveal the awareness of the distinctive essential features that cause the same technical result that is achieved in the claimed method. Therefore, the claimed invention meets the "inventive step" requirement of patentability.

Brief Description of Drawings

The claimed method is illustrated by drawings, which show:

fig. 1 - the structure of preparation and processing of metadata records in the implementation of the method of cryptographic recursive 2-D control of the integrity of the metadata of electronic documents files;

fig. 2 is a diagram explaining the cyclical nature of operations of cryptographic transformation of metadata of electronic documents files;

fig. 3 - a variant of the implementation of the cryptographic transformation function

посредством ключевой хэш-функции;

through a key hash function;

fig. 4 - a variant of the implementation of the cryptographic transformation function

посредством электронной цифровой подписи;

by means of an electronic digital signature;

tab. 1 - data stored metadata records and signature values;

tab. 2 - presentation of the metadata of the electronic document file "Order of the head.doc" in the process of editing by authorized users;

tab. 3 - submission of metadata records of the electronic document file “Order of the head. doc "in hexadecimal notation HEX (ANSI code).

Implementation of the claimed method

The method of cryptographic recursive 2-D control of the integrity of metadata of electronic document files is carried out as follows.

The set of keys K _{U is} divided into two subsets:

и

and

и

moreover, each subsets

and

where q = 1, ..., 3, for all

являются внутренними системными ключами, ключи

- внешними ключами администратора системы, ключи

- внешними ключами оператора системы. При выполнении операции записи и редактирования файлов электронных документов в моменты времени t_l,t₂,…,t_k в памяти системы обработки данных формируются строки:In the considered embodiment of this method, the keys

are internal system keys, keys

- system administrator foreign keys, keys

- external keys of the system operator. When performing the operation of recording and editing electronic document files at times t _l , t ₂ , ..., t _k , the following lines are formed in the memory of the data processing system:

m (t ₁ ) = [z ₁₁ … z _1i ], m (t ₂ ) = [z ₂₁ … z _2i ],…, m (t _k ) = [z _k1 … z _ki ],

containing metadata records z _jl , z _j2 ,…, z _ji for all j = 1,…, k and columns:

which are the details of the files of electronic documents processed by the AIS.

Cryptographic transformation operations are performed over records z ₁₁ , ..., z _1i in the corresponding columns at time t ₁ (Fig. 1):

на ключах

on keys

as a result of which the values of signatures P ₁₁ , ..., P _{1i are formed} .

A concatenation operation is performed over each pair of the obtained signature values Р ₁₁ , ..., P _1i and metadata records z ₂₁ , ..., z _2i , changed at time t ₂ :

over the results of which cryptographic transformation operations are performed (Fig. 1):

after which the operations on the metadata records are performed in a similar order (Fig. 2) within each column:

M _i (t ₁ , t ₂ ,…, t _k ) = [z _1i z _2i … z _ki ],

in accordance with the times t ₃ , t ₄ , ..., t _k .

At the same time, in the line m (t ₁ ) = [z ₁₁ ... z _1i ], at the time t ₁ , operations of cryptographic transformation of all records z ₁₁ , ..., z _1i , metadata of the row are performed (Fig. 1):

и

соответственно.resulting in signature values

and

respectively.

Concatenation operations are performed over the obtained signatures and subsequent records z _21, ... _, z _{2i of the} metadata of the string m (t ₂ ) = [z ₂₁ ... z _2i ], which were changed at time t ₂ :

и

and

over the results of which a cryptographic transformation operation is performed (Fig. 1):

на ключах

on keys

на ключах

on keys

As new metadata records arrive, the operations are repeated in a similar order (Fig. 2) in accordance with the times t ₃ , t ₄ , ..., t _k .

All metadata records:

[z ₁₁ ,…, z _1i ],…, [z _k1 ,…, z _ki ]

and the corresponding signatures:

are stored in the memory of the data processing system in the form of a data table (Table 1).

The integrity of records is controlled based on the extraction of signature data from the table:

and records:

that have passed the storage procedure and are subject to integrity control, over which repeated cryptographic transformation operations are performed. As a result, the newly computed signatures:

are matched pairwise with previously extracted ones:

The conclusion about the absence of violation of the integrity of signatures is made when fulfilling the equalities:

где q=1,…,3, j=1,…,k,

where q = 1, ..., 3, j = 1, ..., k,

otherwise, it is concluded that the integrity of the corresponding signature numbers has been violated.

A feature of the above method is the possibility of its implementation in two versions.

является ключевой хэш-функцией (фиг. 3), причем как на этапе подготовки, так и на этапе контроля целостности записей метаданных выполняется равенство

где q=1,…,3, для всех

In the first case, the cryptographic transformation operation

is a key hash function (Fig. 3), and both at the stage of preparation and at the stage of monitoring the integrity of metadata records, the equality

where q = 1, ..., 3, for all

может являться электронной цифровой подписью (фиг. 4), включающей в себя последовательно выполняемые преобразования бесключевой хэш-функции и функцию ассиметричного криптографического преобразования, причем

то есть на этапе подготовки записей метаданных файлов электронных документов используется подмножество ключей

а на этапе контроля целостности записей метаданных используется подмножество ключей

In the second case, the cryptographic transformation operation

can be an electronic digital signature (Fig. 4), which includes sequentially performed transformations of a keyless hash function and an asymmetric cryptographic transformation function, and

that is, at the stage of preparing metadata records of electronic documents files, a subset of keys is used

and at the stage of integrity control of metadata records, a subset of keys is used

The correctness and practical feasibility of this method is justified by the following example.

Example

Let "Order of the head.doc" be an electronic document file edited by authorized users at times t ₁ , t ₂ , ..., t _k , and containing records z _j1 , z _j2 , ..., z _{ji of} metadata for all j = 1, ... , k,

corresponding to table 2.

Further, in order to simplify the implementation of cryptographic transformations, we will encode the letter designations of the metadata records of the electronic document file "Order of the head.doc" into an information sequence of characters using the hexadecimal number system HEX (ANSI code) (Table 3).

Let's carry out cryptographic transformations in accordance with the declared method based on the hash function of the md5 algorithm.

In columns:

в результате чего образуются значения соответствующих P_ji хэш-кодов:hash calculation operations are performed

as a result, the values of the corresponding P _ji hash codes are formed:

- at time t ₁ :

- at time t ₂ :

- at time t _k :

At the same time, in the lines:

от всех записей метаданных строки, в результате чего образуются значения соответствующих P_j хэш-кодов:m (t ₁ ) = [z ₁₁ … z _1i ], m (t ₂ ) = [z _2l … z _2i ],…, m (t _k ) = [z _kl … z _ki ] the hash function is calculated

from all metadata records of the string, resulting in the values of the corresponding P _j hash codes:

- at time t ₁ :

- at time t ₂ :

- at time t _k :

The calculated signatures are stored in the memory of the AIS data processing system for the purpose of subsequent control of the integrity of the metadata records of the above file of the electronic document "Order of the head.doc".

Let's check the integrity of the record z _{k1 of the} metadata of the electronic

Приказ №235/1» (ANSI-код:

), выполним повторное вычисление хэш-функции в столбце:document "Order of the head ..doc". Why do we extract the corresponding record from the data table in this case “

Order No. 235/1 "(ANSI-code:

), let's recalculate the hash function on the column:

as a result, we get a hash code:

then we re-compute the hash function of the string

as a result, we get a hash code:

сравниваем с ранее извлеченными

из таблицы данных памяти системы обработки данных АИС, получаем:Received hash codes

compare with previously extracted

from the data table of the memory of the AIS data processing system, we get:

Thus, it is possible to make a conclusion about the absence of violation of the integrity of signatures, respectively, the record "z _k1 Order No. 235/1" of the metadata is not changed.

), с целью нарушения управления документом и затруднения в его поиске.Consider the case where the authorized user (insider) was modified illegally recording z metadata ₂₁ "Order №235» on «Instruction №19» (ANSI-code:

), with the aim of disrupting the control of the document and making it difficult to find it.

происходят следующие изменения:Let's repeat the above operations in order to track changes in the table of metadata records. Starting from time t ₂ in the column

the following changes occur:

- at time t ₂ :

- at time t _k :

In turn, in the lines m (t ₂ ) = [z ₂₁ … z _2i ],…, m (t _k ) = [z _kl … z _ki ], the following changes occur:

- at time t ₂ :

- at time t _k :

On the basis of which, when monitoring the integrity of metadata records, the procedure of which is described above, the following will become clear:

which allows us to conclude about the integrity of the metadata records contained in the line m (t ₁ ) = [z ₁₁ … z _1i ].

Checking the integrity of the string m (t ₂ ) = [z ₂₁ ... z _2i ] will show the result:

which indicates the presence of unauthorized modified metadata records on this line.

Based on the information received, in order to determine the number of the unauthorized modified (modified) metadata record (s), we will control their integrity in the columns corresponding to the time t ₂ . The results of which will be presented as follows:

Let's check the integrity of the string m (t _k ) = [z _k1 ... z _ki ], the result is:

We repeat the same operations for the columns corresponding to the time t _k .

The results look like this:

строк m(t₂)=[z₂₁…z_2i], m(t_k)=[z_kl…z_ki] и

столбца M₁(t₁,t₂,…,t_k)=[z₁₁z_2l…z_k1].The results obtained allow us to conclude that the metadata record numbered z ₂₁ was unauthorizedly modified, which in turn caused a subsequent change in hash codes.

rows m (t ₂ ) = [z ₂₁ … z _2i ], m (t _k ) = [z _kl … z _ki ] and

column M ₁ (t ₁ , t ₂ ,…, t _k ) = [z ₁₁ z _2l … z _k1 ].

Thus, the given example has shown that the claimed method of cryptographic recursive 2-D control of the integrity of metadata of electronic documents files functions correctly, is technically feasible and allows solving the problem.

Claims (3)

1. A method of cryptographic recursive 2-D control of the integrity of metadata of electronic documents files, which consists in the fact that the integrity of metadata during the operation of writing and editing electronic document files is controlled due to the fact that records zj1, zj2, ..., zji of metadata are generated, cryptographic converting metadata records zj1, zj2,…, zji using a set of keys KU, two-place concatenation operations are performed

over different records zj1, zj2, ..., zji of metadata and values P (j-1) 1, P (j-1) 2, ... P (j-1) i signatures calculated at the previous iteration step, the results are stored in memory data processing systems for subsequent control of the integrity of the metadata stream, characterized in that the set of keys is divided into two subsets

and

moreover, each subsets

and

where q = 1, ..., 3, for all

when performing the operation of recording and editing electronic document files at times t1, t2,…, tk, the lines m (t1) = [z11… z1i], m (t2) = [z21… z2i],…, m (tk) = [zkl… zki] containing metadata records zj1, zj2,…, zji for all j = 1,…, k and columns M1 (t1, t2,…, tk) = [z11z21… zk1], M2 (t1, t2,…, tk) = [z12z22… zk2],…, Mi (t1, t2,…, tk) = [z1iz2i… zki], over the metadata records z11,…, z1i in the corresponding columns at time t1 cryptographic conversion operations are performed

on keys

as a result of which the values of signatures P11, ..., P1i are formed, then over each pair of obtained values of signatures P11, ..., P1i, and metadata records z21, ..., z2i, changed at time t2, a concatenation operation is performed

over the results of which cryptographic transformation operations are performed

after which operations on metadata records are performed in a similar order within each М1 (t1, t2,…, tk) = [z11z21… zk1], M2 (t1, t2,…, tk) = [z12z22… zk2],…, Mi ( t1, t2,…, tk) = [z11z21,… zk1], column in accordance with the times t3, t4,…, tk, while in the row m (t1) = [z11 ... zli], at the time t1, operations of cryptographic transformation of all records z11, ..., z1i, string metadata are performed

on keys

and

on keys

resulting in signature values

and

respectively, after which concatenation operations are performed on the received signatures and subsequent records z21, ..., z2i of the metadata of the string m (t2) = [z21 ... z2i], which were changed at time t2

and

over the results of which a cryptographic transformation operation is performed

on keys

and

on keys

as new metadata records arrive, operations are repeated in a similar order in accordance with the times t3, t4,…, tk, all metadata records [z11,…, z1i],…, [zk1,…, zki] and the corresponding signatures

are stored in the memory of the data processing system in the form of a data table, control of the metadata integrity is carried out based on the extraction of signature data from the table

and records

passed the storage procedure and subject to integrity control, repeated cryptographic transformation operations on the extracted records

the result of which is the computation of signatures

and then pairwise comparison of the received signatures with the previously saved

signatures, the conclusion about the absence of violation of the integrity of signatures is made when the equalities

where q = 1, ..., 3; j = 1, ..., k, otherwise it is concluded that the integrity was violated for the corresponding signature numbers. 2. A method of cryptographic recursive 2-D control of the integrity of metadata of electronic documents files according to claim 1, characterized in that the operation of cryptographic transformation

is a key hash function, while both at the stage of preparation and at the stage of controlling the integrity of metadata records, equality

where j = 1, ..., 3, for all

3. The method of cryptographic recursive 2-D control of the integrity of metadata of electronic documents files according to claim 1, characterized in that the operation of cryptographic transformation

is an electronic digital signature that includes sequentially performed transformations of a keyless hash function and an asymmetric cryptographic transformation function, while

that is, at the stage of preparing metadata records of electronic documents files, a subset of keys is used

and at the stage of integrity control of metadata records, a subset of keys is used

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