WO2005043806A1 - Encryption/recording device and method - Google Patents

Abstract

It is possible to obtain a smooth video display not interrupted by a decryption key modification processing when performing a special reproduction such as fast-feed reproduction and search. There is provided an encryption/recording device including: information supply means (20) supplied with encoded data containing an encoding unit having an in-frame encrypted image (I picture) and other encoded image (P picture, B picture); encryption processing means (100) for encrypting the encoded data from the information supply means (20) for each predetermined encryption unit and modifying an encryption key for every one or more encryption units; and recording means (40) for recording the encrypted data. When the encryption key modification timing is in the middle of encryption of the in-frame encoded image (I picture), the encryption processing means (100) delays the key modification timing so that the encryption key modification timing is not in the middle of the in-frame encoded image (I picture).

Description

 Specification

 Encryption recording apparatus and method

 Technical field

 The present invention relates to an encryption recording apparatus and method for encrypting and recording encoded data such as an MPEG stream.

 Background art

 [0002] In recent years, with the development of multimedia technology, technology for efficiently recording and reproducing digital video data has been developed. When recording digital video data or the like, it is often desired to perform recording with a predetermined encryption key in view of copyright protection. It is desired that the encryption key be difficult to decrypt the data in order to ensure the security of the data. For example, as one of the encryption methods that make it difficult to decrypt data, there is a method in which one content is divided into a plurality of areas, and the encryption key is changed for each area to perform encryption. On the other hand, when playing back digital video data or the like that has been encrypted, it is desirable to perform efficient decryption and display a smooth screen in order to perform smooth playback.

 [0003] The digital signal recording device described in Patent Document 1 encrypts a digital signal with a key obtained by performing a predetermined operation on key information when recording the digital signal, and converts the encrypted data into key information. Is recorded on a recording medium together with the program. When the digital signal is reproduced, the recording medium reproduces the encrypted data reproduced with the key obtained by performing a predetermined operation on the reproduced key information, and outputs the decrypted data. As a result, even if the key information on the recording medium is obtained, the key cannot be obtained unless a predetermined operation is performed during reproduction. Patent Document 1 discloses that data security is improved by changing encryption keys at regular intervals.

 [0004] Patent Document 1: International Publication No. OOZ52690 pamphlet

 Disclosure of the invention

 Problems to be solved by the invention

[0005] However, according to the above-described conventional technique, the digital signal is encrypted while changing the encryption key at regular intervals. Therefore, one I-picture in the GOP (Group of picture) The encryption key may be changed while the key is being encrypted. In such a case, one I-picture is encrypted with a plurality of encryption keys, and when reproducing a digital signal, one I-picture requires a plurality of decryption keys. When decoding one I-picture with a plurality of decoding keys, for example, when performing special playback such as fast-forward playback or search, smooth video display cannot be performed due to the intervening process of changing the decoding key. There was a problem. An example of the problem to be solved by the present invention is the above-mentioned problem.

 [0006] The present invention has been made in view of the above, and when performing special playback such as fast-forward playback or search, an encryption key capable of displaying a smooth image without a change process of a decryption key intervenes. It is an object of the present invention to obtain a recording apparatus and method.

 Means for solving the problem

 [0007] In order to solve the above-described problems and achieve the object, an invention according to claim 1 is an input apparatus to which coded data constituted by a coding unit including at least an intra-frame coded image is input. Means for encrypting the encoded data in a predetermined encryption unit, and encrypting the encoded data while changing an encryption key for each of one or a plurality of encryption units; and A recording means for recording the encrypted encoded data on a recording medium, wherein the encryption processing means encrypts the one intra-frame encoded image during encryption. At least one intra-frame encoded image is encrypted with a single encryption key so that the encryption key is not changed.

 [0008] Further, according to the invention described in claim 6, encoded data composed of encoding units including at least an intra-frame encoded image is encrypted in a predetermined encryption unit while changing an encryption key. In the encryption recording method of encoding and recording, at least one intra-frame encoded image is converted into a single encrypted key so that an encryption key is not changed during encryption of the one intra-coded image. It is characterized in that it is encrypted.

 Brief Description of Drawings

 FIG. 1 is a block diagram for explaining a configuration of an encryption and recording apparatus according to a first embodiment.

 FIG. 2 is a diagram showing information stored in storage means.

FIG. 3 is a diagram showing information recorded in a recording medium. O

 FIG. 4 is a diagram for explaining the relationship between CBC and pictures.

 [Figure 1-

 [5] FIG. 5 is a flowchart illustrating a processing procedure from encryption to recording of the encryption and recording apparatus according to the first embodiment.

 FIG. 6 is a block diagram for explaining a configuration of the encryption device according to the second embodiment.

 FIG. 7 is a diagram for explaining the relationship between CBC and GOP.

 FIG. 8 is a flowchart showing a procedure for inserting a NULL packet.

 Explanation of symbols

 Encryption recording device

 15 Encryption recorder

 20 Information supply means

 21 Key change prohibition flag

 30 means of encryption

 31 CBC counter

 32 Key generation means

 40 Recording means

 50 Recording media

 60 CPU

 62 Memory

 70 Encryption key supply means

 80 Encryption key generation means

 100 Encryption processing means

 BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, embodiments of the encryption device and method according to the present invention will be described in detail with reference to the drawings. The present invention is not limited by the embodiment. Hereinafter, the outline and characteristics of the encryption device of the present invention will be described as an embodiment, and thereafter, examples of the encryption device will be described.

[0012] [Embodiment] In the present embodiment, the content to be subjected to encryption processing is encoded data such as MPEG-TS (Motion Picture Expert Group-Transport Stream). In addition, the content includes an intra-frame encoded image encoded only with information in the own frame, such as an I picture in MPEG, and other encoded images! Examples of other images include, for example, a picture force located in the past in time, such as a P picture in MPEG, and an inter-frame forward prediction code created by predicting a picture, and a time, such as a Z or B picture. Inter-frame bi-directional predictive coded images that are created by predicting the picture powers located in front of and behind the image are expected. In MPEG, a GOP (Group of picture), which is a coding unit, is composed of a combination of an I picture, a P picture, and a B picture. There are various types of GOPs, but one GOP always has at least one I-picture.

 [0013] On the other hand, encryption methods such as DES (Data Encryption Standard), 3DES, and AES (Advanced Encryption Standard) are used, and encryption is performed every predetermined data length (64, 128, 256 knots). The cipher block chaining method (Cipher Block Chaining: CBC) is adopted from the viewpoint of plaintext protection. The encryption key is changed in units of one or more CBC blocks. That is, in the present embodiment, encoding data such as MPEG-TS is encrypted for each predetermined encryption unit, and the encryption key is changed for each one or more encryption units. An encryption process is performed.

 [0014] When such encoded data is encrypted on a predetermined encryption unit basis and recorded on a recording medium, a section meaningful in the encoded data and a length of the encryption unit are defined. There is no correlation between them. The meaningful section in the encoding data indicates a break in a picture or a GOP in the case of MPEG.

[0015] Therefore, in the method of changing the encryption key at regular intervals, the encryption key may be changed when one intra-frame encoded image (I-picture in MPEG) is encrypted. is there. That is, one intra-frame encoded image is encrypted using a plurality of encryption keys, and a plurality of decryption keys are required to reproduce this portion. In fast-forward playback, search, etc., the ability to extract and reproduce only intra-frame encoded images (I-pictures). Image cannot be displayed.

 [0016] Therefore, in the present embodiment, an encoded image including at least one intra-frame encoded image is encrypted using the same encryption key.

 [0017] For example, when the encryption key change timing, which is the timing for changing the encryption key when encrypting the encoded data, is in the middle of encrypting the intra-frame encoded image, the encryption key change is performed. By delaying the change timing so that the timing is not in the middle of encrypting the intra-frame encoded image, the intra-frame encoded image is encrypted with the same encryption key, or the encryption key change timing is changed. When the encoding unit including the intra-frame encoding image is in the middle of encryption, the encryption key change timing is not in the middle of encrypting the encoding unit. By inserting information having a meaning such as the above, the encoded image including at least one intra-frame encoded image is encrypted with a single encryption key.

 As described above, in the embodiment, since the timing for changing the encryption key is not set in the middle of the intra-frame encoded image, at least one intra-frame encoded image is changed using the same encryption key. Encryption can be performed, so that at least one intra-frame encoded image can be decrypted with the same decryption key. Therefore, smooth video display can be performed during fast-forward playback or search.

 [Example 1]

 FIG. 1 is a block diagram for explaining a configuration of the encryption device according to the first embodiment of the present invention. An encryption recording device 10 applied to an iVDR (Intelligent Video Digital Recorder) or the like is a device that encodes and encodes encoded data such as MPEG-TS in real time and records the information. It comprises a processing means 100, a recording means 40, a CPU (Central Processing Unit) 60 as a control means, and a storage means (RAM) 62. The encryption processing means 100 includes an encryption means 30, an encryption key supply means 70, and an encryption key generation means 80. The encryption device 10 is connected to a recording medium 50.

[0020] The information supply means 20 is an input means to which encoded data is input from the outside, and is connected to the encryption means 30, the encryption key supply means 70, and the CPU 60. The start and stop of the operation of the information supply means 20 are controlled by a control signal from the CPU 60, and the information supply means 20 is externally input. The partial TS (Transport Stream) signal is supplied to the encrypting means 30 at a predetermined timing while buffering for each data size to be encrypted by the encrypting means 30! The partial TS signal is obtained by extracting information necessary for recording and reproduction from the MPEG-TS signal.

 [0021] Further, the information supply means 20 has data identification means (not shown) for determining whether to prohibit key change based on the input partial TS signal! / Puru. The data identification means changes the state of the key change prohibition flag as an identification flag for identifying whether or not to prohibit the change of the encryption key, according to the determination result. The key change prohibition flag is set to “1” when key change is prohibited, and set to “0” when key change is permitted.

 Here, the video data encoded (encoded) by MPEG is packetized with a predetermined size such as 188 bytes or 192 bytes. In MPEG encoding, the information compression ratio differs depending on video data and the like, and video data is composed of I-pictures, B-pictures, P-pictures, etc., whose data length is indefinite.

 As described above, an I picture is an intra-frame coded image that is encoded only with information in its own frame, and does not use correlation information of another screen that precedes and follows in time. I-pictures are arranged at regular intervals in video data. The P picture is an inter-frame forward predictive coding image created by prediction from an I picture or a P picture located in the past in time. The B picture is an inter-frame bidirectional predictive encoded image created by also predicting the I picture and the P picture power located before and after in time.

 [0024] In addition, a GOP (

Group of picture). There are various types of GOPs. For example, one GOP is composed of 15 pictures (frames) of IBBPBB PBBPBBPBB, and one! / Is composed of 18 pictures (frames) of IBBPB BPBBPBBPBBPBB. I do. There is always at least one I-picture in one GOP.

[0025] The information supply means 20 detects an I picture in the input partial TS signal in order to determine whether or not the picture to be encrypted by the encryption means 30 is an I picture. The key change prohibition flag is set to “1” while the I picture is detected, and set to “0” during the period when no I picture is detected. The information supply means 20 is, for example, an I picture The time until the beginning of another B-picture or P-picture is detected is the I-picture detection period. The key change prohibition flag is set to “1” during the detection period, and set to “0” during periods other than the I-picture detection period. This key change prohibition flag can be referred to by the encryption key supply means 70.

 When receiving the key generation notification signal from CPU 60, encryption key generation means 80 generates a new encryption key and sends the generated encryption key to encryption key supply means 70. The key generation notification signal sent from the CPU 60 to the encryption key generation means 80 indicates the encryption key change timing, and the transmission time interval is set by a timer, a counter, or the like. A key generation notification signal is generated for each CBC block number. That is, the encryption key generation means 80 sequentially generates different encryption keys in response to the key generation notification signal, and sends the generated encryption keys to the encryption key supply means 70.

 [0027] The encryption key supply means 70 holds the encryption key input from the encryption key generation means 80, and transfers the held encryption key at a timing determined according to the state of the key change prohibition flag. And output to the storage means 62. That is, when the key change prohibition flag is “0”, the encryption key supply means 70 immediately outputs the encryption key input from the encryption key generation means 80 to the encryption means 30. In the case of "l", even if the encryption key is input from the encryption key generation means 80, the encryption key is not output to the encryption means 30 at this point, the encryption key is retained, and the key change prohibition flag is set. The encryption key is output to the encryption means 30 at the time corresponding to the boundary position between the first encryption blocks after the time when the value changes from “1” to “0”. As described above, in this case, the encryption key supply unit 70 adjusts the key change timing at the time of encryption in the encryption unit 30.

The encryption means 30 includes a CBC (Cipher Block Chaining) counter 31 that counts the number of encryption blocks (CBC blocks), which are encryption units. The information supply means 20 and the encryption key supply means 70 , Recording means 40 and CPU 60. The encryption means 30 performs encryption on the partial TS signal input from the information supply means 20 for each fixed-length encryption block using the encryption key input from the encryption key supply means 70. Output the encrypted partial TS signal (hereinafter referred to as encrypted data) to the recording means 40 To do. The CBC counter 31 counts the number of encrypted CBC blocks, and outputs the count result to the storage means 62 via the CPU 60. As described above, the CBC is a cipher that adds the previous ciphertext to the current plaintext and encrypts the result using DES (Data Encryption Standard), 3DES, AES (Advanced Encryption Standard), etc. It is a block chain method.

[0029] The recording means 40 causes the recording medium 50 to record the encrypted data obtained from the encryption means 30 and the management information of the encrypted data obtained from the CPU 60 (temporarily stored in the storage means 62). The recording medium 50 is a recording medium such as an optical recording medium such as a hard disk or a DVD, and the recording medium 50 records the encrypted data sent from the recording means 40 and management information of the encrypted data.

 The CPU 60 controls the components (the information supply means 20, the encryption means 30, the recording means 40, the encryption key supply means 70, and the encryption key generation means 80) of the encryption recording device 10 as a whole. Then, the management information of the encrypted data encrypted by the encryption means 30 is temporarily stored in the storage means 62. Further, the CPU 60 outputs the above-mentioned key generation notifying signal as the encryption key change timing signal to the encryption key generation means 80 at a constant time interval corresponding to a predetermined number of CBC blocks, for example.

 Next, management information stored in the storage unit 62 will be described. FIG. 2 shows a specific example of the management information stored in the storage means 62. The management information includes a key application number A and key application range information B1—Bn (n is a natural number). The key application number A indicates the number n of keys used at the time of encryption by the encryption means 30, that is, the number of key application range information B1 to Bn. Key application range information B1—Bn consists of key information X, key application start CBC number Y, and key application CBC number Z. The key information X is information indicating the encryption key used at the time of encryption by the encryption means 30, that is, the encryption key generated by the encryption key generation means 80. Will be the decryption key of

 The key application start CBC number Y is the number of the CBC block where the application of the key X is started.

For example, if key X is also applied to the 10th CBC blocking force, the starting CBC number Y will be 10. The key application CBC number Z indicates the number of CBCs to which key X is applied. For example, if key X is applied from the 10th CBC block to the 15th CBC block, Applicable CBC number Z is 6.

 Next, information recorded on the recording medium 50 will be described. FIG. 3 shows information recorded in the recording medium 50. The information written to the recording medium 50 is composed of the above-mentioned management information file and encrypted data.

 [0034] The management information file includes information for managing the encrypted data recorded on the recording medium 50. Like the management information temporarily stored in the storage unit 62, the key application number A and the key It has use range information B1—Bn. Each of the key application range information B1 to Bn is composed of key information X, key application start CBC number Y, and key application CBC number, as described above. The encrypted data recorded on the recording medium 50 is information such as a partial TS encrypted by the encrypting means 30.

 Next, a method of delaying the encryption key change timing by the key generation notification signal instructed by the CPU 60 will be described. In the first embodiment, in order to smoothly perform fast-forward playback or the like performed by extracting an I-picture or the like, one I-picture is the same so that one I-picture is not decrypted with a plurality of different decryption keys. Encrypt with an encryption key.

 When recording while receiving MPEG-TS or the like, it is difficult to recognize in advance the length of the data of each I-picture because of real-time processing. Also, it is difficult to predict what effect a NULL (null) packet, etc., will have between pictures in the original MPEG-TS data. Therefore, in the first embodiment, the timing for performing the key change is delayed by referring to the state of the key change prohibition flag so that one I-picture cannot be decrypted with a different decryption key. Te ru.

FIG. 4 is a diagram for explaining the relationship between CBC blocks and pictures. In FIG. 4, the CBC block for encryption has a fixed length.In the initial stage, for example, an encryption key is changed every three CBC blocks by a key generation notification signal instructed by the CPU 60. It is assumed that the key change timing is set as follows. In the initial stage, in Fig. 4, the first three CBC blocks 1 (CBC1) are encrypted with the same first encryption key, and the next three CBC blocks 2 (CBC2) are encrypted. It is assumed that the encryption is performed using a second encryption key different from the encryption key of the first time, and that the time point a is the key change timing in the initial stage. That is, the encryption key change timing at the initial stage by the key generation notification signal At the time point a, a new second encryption key is input from the encryption key supply means 70 to the encryption means 30 at time point a, and the CBC block in section b is encrypted by the second encryption key in the initial stage. Suppose that it was a CBC2 block.

 In this case, the initial key change timing a based on the key generation notification signal instructed from the CPU 60 is in the middle of the I picture. For this reason, the I picture is encrypted with two types of encryption keys. Therefore, in the first embodiment, the key change timing is delayed so that one I picture is not encrypted using a different encryption key. Here, the key change timing is delayed by one CBC block, which is a unit of encryption, and the new key change timing is set to time point c.

 In other words, at time point a, which is the key change timing in the initial stage, the key change prohibition flag is 1, so that at this time point a, the encryption key supply means 70 transmits the new second encryption key to the encryption key. Do not input to column 30. The encryption key supply means 70 inputs a new second encryption key to the encryption means 30 at the boundary time point c of the first CBC block after the key change prohibition flag becomes 0. Therefore, at time point a, no key change is performed in the encryption unit 30, and the encrypted block in section b is a B-encoded block CBC1 encrypted using the first encryption key. Then, the three CBC blocks after the time point c become an encrypted block CBC2 which is encrypted using the second encryption key! /.

 [0040] In this way, one I picture is encrypted using only the encryption key of CBC1. If one I-picture is encrypted with one encryption key, one I-picture can be decrypted with one decryption key. In the case of FIG. 4, one I-picture can be encrypted using the same encryption key only by changing one CBC2 to CBC1, but depending on the length of the I-picture, CBC2 and CBC3 may be changed to CBC1.

In the case of FIG. 4, the number of CBC blocks (CBC2) to be encrypted with the second encryption key is set in the initial stage, even though one CBC2 is changed to CBC1. The number of CBC blocks changed from CBC2 to CBC1 (one in this case) is encrypted with the second encryption key. The number of CBC blocks (CBC2) to be used may be reduced. In that case, the number of CBC blocks (CBC2) in Fig. 4 is two It becomes.

 Next, the operation of each component shown in FIG. 1 will be described in detail with reference to the flowchart in FIG. Fig. 5 is a software flow chart showing the hardware flow of each component shown in Fig. 1.

 When the recording operation is started, an initialization process for clearing the storage unit 62, the CBC counter 31, and the key change prohibition flag 21 is performed (Step S100).

 Next, the encryption key generation unit 80 generates a first encryption key, and supplies the generated encryption key to the encryption key supply unit 70 (Steps S 110 and S 120). At the start of recording, the encryption key supply means 70 immediately outputs the encryption key supplied from the encryption key generation means 80 to the encryption means 30 unconditionally, that is, without referring to the key change prohibition flag. Further, the encryption key supply means 70 outputs the encryption key supplied from the encryption key generation means 80 to the CPU 60.

 Next, the encryption unit 30 enters a state of waiting for data input to wait for data to be input in an encryption process using the encryption key supplied from the encryption key generation unit 80 ( Step S 130). Further, the recording means 40 also enters a data input waiting state of waiting for recording processing until data to be recorded is input (step S140).

 Next, when the partial TS signal is input, the information supply unit 20 starts a picture detection operation in the input partial TS signal (step S 150).

 That is, when the partial TS signal is input, the information supply unit 20 supplies the input partial TS to the encryption unit 30 at a predetermined timing while buffering the input partial TS for each predetermined data size. At the same time, in order to determine whether the picture to be encrypted by the encryption means 30 is an I picture, the head of the I picture in the input partial TS signal is detected (step S160). The information supply means 20 detects the head of the I picture by detecting the head of the I picture or a similar sequence header code (SHC), GOP header, or the like.

Then, upon detecting the beginning of the I picture, the information supply unit 20 raises the key change prohibition flag from “0” to “1”. The key change prohibition flag is held at `` 1 '' until the start of another B picture or P picture is detected, and `` 0 '' at the point where the start of another B picture or P picture is detected (step S180). (Step S190). In this way, I picture The key change prohibition flag is held at “1” during the period when the key is detected, and the key change prohibition flag is set to “0” during the period when no I-picture is detected. The information supply means 20 repeatedly executes the processing of steps S160 to S190.

 On the other hand, when the partial TS signal is input to the information supply means 20, the information supply means 20 is also notified to that effect to the CPU 60. As a result, the CPU 60 increments the value of the key application number A by +1 and stores the result of the +1 (in this case, the key application number A = 1) in the storage area of the key application number A of the storage means 62 (step S200).

 Further, the CPU 60 stores the first encryption key to which the encryption key supply means 70 was also supplied at the time of step S120 in the storage area of the key information X of the storage means 62 (step S210). ). Further, the CPU 60 obtains the count output of the CBC counter 31 of the encryption means 30 and stores the obtained count result (in this case, the initial value of the CBC counter 31). It is stored in the area (step S220).

 Next, until the encryption key generation means 80 receives the key generation notification signal from the CPU 60 (step S230, No), the encryption key generation means 30 receives the partial TS signal from the information supply means 20. From the point in time, in step S110, encryption processing is performed in CBC block units using the first encryption key input from the information supply means 20. That is, the encryption unit 30 sequentially encrypts the partial TS signal input from the information supply unit 20 in CBC block units using the first encryption key in CBC block units, and encrypts the encrypted partial TS signal. The buffer unit sequentially outputs the TS signal, that is, the encrypted data, to the recording unit 40 while buffering the data in units of CBC blocks (step S240). When one CBC block is encrypted, the CBC counter 31 increments its count by +1 and outputs the count to the CPU 60 (step S250). Further, the recording means 40 sequentially records the encrypted data input from the encryption means 30 in a required area of the recording medium 50 sequentially (step S260). As described above, the encryption processing using the first encryption key in the encryption means 30, the increment of the CBC counter 31, and the recording operation in the recording means 40 are performed according to the key generation notification signal from the CPU 60. Repeated until 80 is entered.

[0052] Thereafter, when a key generation notification signal from CPU 60 is input to encryption key generation means 80 (Step S230, Yes), encryption key generation means 80 generates and generates a second encryption key. The second encryption key is output to the encryption key supply means 70. The encryption key supply means 70 holds the input second encryption key and refers to the state of the key change prohibition flag 21 of the information supply means 20 (step S290). In this case, it is assumed that the key change prohibition flag 21 of the information supply means 20 is “0”.

Since the key change prohibition flag is “0” (No in step S290), the encryption key supply unit 70 immediately converts the held encryption key input from the encryption key generation unit 80 into the encryption key. Output to 30 and CPU 60 (step S330). The CPU 60 performs an operation of subtracting the value of the key application start CBC number Y obtained in step S220 from the count value of the CBC counter 31 at this time, and stores the operation result in the storage means 62 as the key application CBC number Z. (Step S340). That is, in this case, in step S340, the key application CBC number Z in the encryption processing using the first encryption key, which is performed by repeating steps S230 to S260, is calculated.

 Next, the CPU 60 increments the value of the key application number A by +1 and stores the result of +1 (in this case, the key application number A = 2) in the storage unit 62 as the key application number A. It is stored in the area (step S200).

 Further, at the time of step S330, the CPU 60 stores the second encryption key to which the encryption key supply means 70 has also been supplied in the storage area of the key information X of the storage means 62 (step S210). . Further, the CPU 60 obtains the count output of the CBC counter 31 of the encryption means 30 at this time, and stores the obtained count result in the storage area of the key application start CBC number Y of the storage means 62 (step S220). .

Next, until the encryption key generation means 80 receives a new key generation notification signal from the CPU 60 (step S230, No), the encryption means 30 is input from the information supply means 20 in step S330. Using the second encryption key, encryption processing is performed for each CBC block. That is, the encryption unit 30 sequentially encrypts the partial TS signal input from the information supply unit 20 in CBC block units using the second encryption key in CBC block units, and converts the encrypted data into CBC blocks. The data is sequentially output to the recording means 40 while buffering in block units (step S240). When one CBC block is encrypted, the CBC counter 31 increments its count by +1 and outputs the count to the CPU 60 (step S250). Further, the recording means 40 sequentially records the encrypted data input from the encryption means 30 in a required area of the recording medium 50 sequentially (step S260). The above-described encryption processing using the second encryption key in the encryption means 30, the increment of the CBC counter 31, and the recording operation in the recording means 40 are performed by a new key generation notification signal from the CPU 60. Repeat until input to encryption key generation means 80.

 [0057] Thereafter, when a key generation notification signal from CPU 60 is input to encryption key generation means 80 (Step S230, Yes), encryption key generation means 80 generates and generates a third encryption key. The third encryption key is output to the encryption key supply means 70. The encryption key supply means 70 holds the input third encryption key and refers to the state of the key change prohibition flag 21 of the information supply means 20 (step S290).

 In this case, it is assumed that the key change prohibition flag 21 of the information supply means 20 is “1”. Since the encryption key supply unit 70 has the key change prohibition flag power “l” (step S230, Yes), the third encryption key input from the encryption key generation unit 80 Do not output to Then, the encryption key supply means 70 holds the third encryption key, and stores the third encryption key between the first encryption blocks after the point at which the key change prohibition flag changes from “1” to “0”. At the time corresponding to the boundary position (time c in FIG. 4), the third encryption key is output to the encryption means 30 (step S330).

 In this case, if the encryption key supply unit 70 immediately inputs the encryption key supplied from the encryption key generation unit 80 to the encryption unit 30, the encryption key supply unit 70 The timing of each part is adjusted so that the encryption key is changed at the boundary. Therefore, the encryption key supply means 70 sets the time (e.g., time point a in FIG. 4) after the input of the encryption key from the encryption key generation means 80, at the time when the time corresponding to one or more CBC blocks has elapsed ( By sequentially detecting the time point c and the time point (1,...) In FIG. 4 using a timer counter or the like, the boundary position between the encrypted blocks is detected, and the key change inhibition flag is changed from “1” to “1”. After detecting the time point corresponding to the boundary position between the first encryption blocks after the time point at which it becomes `` 0 '', the third encryption key is output to the encryption means 30. Good.

[0060] As described above, when the key change prohibition flag is "1", the encryption key supply unit 70 holds the encryption key (the third encryption key in this case) input from the encryption key generation unit 80. , Key change prohibited After the flag changes from “1” to “0”, the encryption key is output to the encryption unit 30 at the time corresponding to the boundary position between the first encrypted blocks (time c in FIG. 4). I am doing it. In this manner, the encryption key supply means 70 delays the timing of supplying a new encryption key (in this case, the third encryption key) to the encryption means 30!

 [0061] Therefore, after a new encryption key (in this case, the third encryption key) is output from the encryption key generation means 80, the encryption key is supplied from the encryption key supply means 70 to the encryption means 30 (in this case, the third encryption key). During the period until the encryption key is supplied, that is, during the delay time by the encryption key supply unit 70, the encryption unit 30 performs encryption using the second encryption key.

 [0062] That is, during this delay time, the encryption means 30 sequentially encrypts the partial TS signal input from the information supply means 20 in CBC block units using the second encryption key in CBC block units. The data is sequentially output to the recording means 40 while buffering the encrypted data in CBC block units (step S300). When one CBC block is encrypted, the CBC counter 31 increments its count by +1 and outputs the count to the CPU 60 (step S310). Further, the recording means 40 sequentially records the encrypted data input from the encryption means 30 in a required area of the recording medium 50 (step S320).

 As described above, the encryption processing using the second encryption key in the encryption means 30, the increment processing in the CBC counter 31, and the recording operation in the recording means 40 are performed when the key change prohibition flag is set to “1”. Is repeated from "" to "0". To be precise, the encryption process using the second encryption key added by changing the key change timing is performed after the key change prohibition flag changes from “1” to “0”, The process is executed until a new third key is supplied to the encryption unit 30.

 In this case, as described above, the encryption key supply unit 70 corresponds to the boundary position between the first encrypted blocks after the point at which the key change inhibition flag changes from “1” to “0”. At the time (time c in FIG. 4), the third encryption key is output to the encryption means 30 and the CPU 60 (step S330).

[0065] The CPU 60 performs an operation of subtracting the value of the key application start CBC number Y obtained in step S220 from the count value of the CBC counter 31 at this time, and stores the operation result as the key application CBC number Z. It is stored by means 62 (step S340). That is, in this case, step S At 340, the key application CBC number Z in the encryption processing using the second encryption key performed by repeating the processing of steps S230 to S260 and performing the processing of steps S300 to S320 is calculated.

Next, the CPU 60 increments the value of the key application number A by +1 and stores the result of the +1 (in this case, the key application number A = 3) in the storage unit 62 as the key application number A. It is stored in the area (step S200).

 Further, the CPU 60 stores the third encryption key to which the encryption key supply means 70 was also supplied at the time of step S330 in the storage area of the key information X of the storage means 62 (step S210). . Further, the CPU 60 obtains the count output of the CBC counter 31 of the encryption means 30 at this time, and stores the obtained count result in the storage area of the key application start CBC number Y of the storage means 62 (step S220). .

 Next, similarly to the above, by repeating the processing of steps S230-S260, the encryption processing using the third encryption key in the encryption means 30, the increment of the CBC counter 31 and the recording means 40 Is performed.

 [0069] Thereafter, when a key generation notification signal from CPU 60 is input to encryption key generation means 80 (step S230, Yes), encryption key generation means 80 generates and generates the fourth encryption key. The fourth encryption key is output to the encryption key supply means 70. The subsequent operation is the same as described above, and whether or not to change the key change timing is determined according to the state of the key change prohibition flag 21 of the information supply means 20, and the encryption according to the determination result is performed. A dani process is performed.

 As described above, according to the first embodiment, when the encryption key change timing occurs in the middle of one I-picture, the change timing of the encryption key is delayed so that one I-picture is replaced by the same encryption key. Since encryption is performed, in a real-time encryption recording apparatus that encrypts while receiving encoded video data such as MPEG-TS and records it on a recording medium, smooth video display during fast-forward playback / search is achieved. It becomes possible.

In the first embodiment, the encryption key supply means 70 adjusts the key change timing at the time of encryption in the encryption means 30. The timing may be adjusted. For example, the encryption means 30 is provided with a buffer for holding two new and old encryption keys. The encryption key supply unit 70 sets the state of the key change prohibition flag 21 By the identification, an identification signal indicating which of the two new and old encryption keys is to be used is input to the encryption means 30. The encryption means 30 selects an encryption key to be used from the two old and new encryption keys with reference to the identification signal each time a CBC block break occurs, and performs encryption using the selected encryption key. In the first embodiment, the CPU 60 instructs the timing to change the encryption key. However, the encryption key change timing may be set in advance in the encryption processing unit 100 itself. The point is that it is only necessary to be able to delay the encryption key change timing so that the encryption key change timing is not in the middle of an I-picture during encryption by the encryption means 30. Try using any other method.

 Further, in the first embodiment, an area in which one I picture is not encrypted with a plurality of encryption keys is protected from being encrypted with a plurality of encryption keys. The area is not limited to one I picture, and may be, for example, an area including one P picture or B picture in addition to one I picture. Further, in the first embodiment, the power encryption method using CBC as the encryption method is not limited to CBC.

 It is desirable that the size of the CBC block and the physical access size of the recording medium 50 be matched, and that the access start position of the content and the start position of the CBC block be matched. That is, if the physical access unit is 512 bytes and only a logical multiple, for example, 6144 bytes, can be accessed, the CBC block size is matched to this access unit. In addition, since the access to the content is performed at the head of the sector of the recording medium including the corresponding access position, if the access start position is matched with the start position of the CBC block, the access to the sector can be performed. At the same time, the CBC block can be accessed, and the decoding process can be simplified.

 [Example 2]

Example 2 will be described with reference to FIGS. 6-8. FIG. 6 is a block diagram for explaining a configuration of the encryption / imagine recording apparatus according to the second embodiment of the present invention. Note that among the components shown in FIG. 6, components that achieve the same functions as the components of the first embodiment shown in FIG. 1 are denoted by the same reference numerals. In the second embodiment, one GOP is decrypted with a plurality of decryption keys. One GOP is encrypted with one encryption key so that it is not encrypted.

As described above, a combination of an I picture, a P picture, and a B picture forms a GOP (Group of picture). Also, one GOP always contains at least one I picture.

 The encryption recording device 15 has an authoring processing function, and includes an information supply unit 20, an encryption processing unit 100, a recording unit 40, a CPU 60, and a storage unit 62. The encryption processing means 100 includes an encryption means 30 and a key generation means 32. Further, the encryption recording device 15 is connected to a recording medium 50. Since the authoring process is a non-real-time process, the size of the input partial TS signal after encoding can be known in advance, and the key change position can be freely determined.

 [0077] The information supply means 20 is supplied with encoded video data such as a partial TS signal from an external storage device. The partial TS signal is composed of a sequence header code (SHC), a plurality of GOPs having an indefinite data length, and the like. That is, the length of the data string including the GOP changes depending on the MPEG encoding method, the number of pixels, and the like. The information supply means 20 is controlled to start and stop the operation by a control signal from the CPU 60, and outputs an externally input partial TS (Transport Stream) signal for each data size encrypted by the encryption means 30. The data is supplied to the encryption means 30 at a predetermined timing while buffering.

 Further, the information supply means 20 acquires from the CPU 60 information on the key change position (key change timing) at the time of the encryption processing performed by the encryption means 30, and the input partial TS. Detects the break position between adjacent GOPs in the signal. Then, the information supply means 20 determines whether or not the force at which the key change position coincides with the separation position between the GOPs, and in the case of a mismatch, there is no meaning at the end of the GOP in other words immediately before the GOP. By performing a process of adding data, that is, a NULL packet, or a private packet including random data, the encryption key change timing encrypts the GOP (encoding unit). Do not be on the way.

[0079] The encryption processing means 100 includes an encryption means 30 including a CBC (Cipher Block Chaining) counter 31 for counting the number of encryption blocks (CBC blocks) as encryption units; Key generation means 32 for sequentially generating different encryption keys at predetermined time intervals or at a fixed number of CBC blocks according to a key generation notification signal from the CPU 60. The encryption unit 30 performs encryption for each fixed-length encryption block on the partial TS signal input from the information supply unit 20 using the encryption key generated by the key generation unit 32, The encrypted encrypted data is output to the recording means 40.

The recording unit 40 causes the recording medium 50 to record the encrypted data obtained from the encryption unit 30 and the management information (temporarily stored in the storage unit 62) of the encrypted data obtained from the CPU 60. The recording medium 50 is a recording medium such as an optical recording medium such as a hard disk or a DVD, and the recording medium 50 records the encrypted data sent from the recording means 40 and management information of the encrypted data.

 The CPU 60 controls the components (the information supply means 20, the encryption means 30, and the recording means 40) of the encryption recording device 15 as a whole, and also controls the encryption performed by the encryption means 30. Data management information is temporarily stored in the storage means 62. Further, the CPU 60 outputs a key generation notification signal as an encryption key change timing signal to the encryption unit 30 at a constant time interval corresponding to, for example, a predetermined number of CBC blocks.

 [0082] As shown in Fig. 2, in the storage means 62, key application number A, key information X, key application start CBC number Y, and key application CBC number Z key application range information B1—Bn Is stored. Further, as shown in FIG. 3, a management information file of the recorded encrypted data and the encrypted data encrypted by the encryption means 30 are recorded on the recording medium 50.

 Next, a process performed by the information supply unit 20 to match the key change timing with the delimiter between GOPs (the head of the GOP) will be described with reference to FIGS. 7 and 8.

 FIG. 7 is a diagram for explaining the relationship between CBC and GOP. In Fig. 7, the CBC block for encryption has a fixed length. In FIG. 7, the first plurality of CBC blocks 1 (CBC1) are encrypted with the same first encryption key, and the next plurality of CBC blocks 2 (CBC2) are encrypted with a second encryption key different from the first encryption key. The encryption key is set so that encryption is performed. That is, the time point a is the key change timing.

[0085] On the other hand, in the partial TS signal in the initial stage input to the information supply means 20, it exists at the time (position) c at which the separation force between one GOP (GOPl) and the next GOP (GOP2) is generated. It is assumed that In this case, in the partial TS signal in the initial stage, the key change timing a is in the middle of GOP2, and GOP2 is encrypted with the first encryption key and the second encryption key.

 Therefore, in the second embodiment, one GOP is encrypted with one encryption key by the information supply means 20 performing a process as shown in FIG.

 [0087] First, when an alignment request is input from CPU 60, information supply means 20 detects a break position between adjacent GOPs in the input partial TS signal, and changes a key at the time of encryption / reduction processing. The position is detected (step S510). The break position between GOPs can be detected by a GOP header or the like. Since the CBC block has a fixed length, the key change position is obtained from the CPU 60 by using information on the key change position (key change timing) such as the CBC block length (fixed length) and the number of CBC blocks for performing encryption with the same key. By obtaining it, it can be derived.

 [0088] The information supply means 20 determines whether or not the obtained break position between GOPs matches the key change position (step S520). As a result of this determination, if the delimiter position between GOPs and the key change position do not match, as shown in FIG. 7, the key change position and the delimiter position between GOPs (the start position of the GOP) must be matched. In other words, a NULL packet is inserted between GOPs, in other words, immediately before the next GOP (step S530).

 In the case of FIG. 7, a NULL packet having a data length matching the key change position a and the delimiter position between GOPs is inserted between GOP1 and GOP2. As a result, GOP2 is encrypted using only the encryption key of CBC2. Thus, when one GOP is encrypted with one encryption key, one GOP can be decrypted with one decryption key.

 As described above, according to the second embodiment, meaningless! ヽ data such as a NULL packet is inserted so that the head position of the GOP coincides with the encryption key change position! / ヽ. In a cryptographic recording device that has a function to authorize encoded video data such as MPEG TS, one GOP is encrypted with one cryptographic key, and special playback such as fast-forward playback and search is performed. Sometimes smooth video display is possible.

[0091] In the second embodiment, the key change position and the break position between the GOPs (the start position of the GOP) Position) and a NULL packet is inserted between GOPs so that they match. However, the following implementation is also possible.

 That is, first, the information supply means 20 detects the data lengths of all GOPs in the input partial TS signal. Then, it is determined whether or not the detected data length of each GOP is an integral multiple of the data length (fixed length) of the CBC block. Then, for a GOP whose data length is not an integral multiple of the data length of the CBC block, a NULL packet is inserted at the end of the GOP so that the data length is an integral multiple of the data length of the CBC block. That is, in this case, a NULL packet is inserted at the end of the immediately preceding GOP so that the beginning of the GOP matches the delimiter of the CBC block. Then, at least one GOP is appropriately changed in the key change position so as to be encrypted with the same key. By doing so, at least one GOP can always be encrypted with one encryption key.

 In the second embodiment, the above-described processing performed by the information supply unit 20 may be performed by the encryption processing unit 100!

Claims

The scope of the claims  [1] input means for receiving encoded data composed of encoding units including at least an intra-frame encoded image;  Encryption processing means for encrypting the encoded data in a predetermined encryption unit, and encrypting the encoded data while changing an encryption key for each of one or a plurality of encryption units; and Recording means for recording the dani data on a recording medium,  The encryption processing means encrypts at least one intra-frame encoded image with a single encrypted key so that an encryption key is not changed during encryption of the one intra-coded image.  An encryption recording device characterized by the above-mentioned.  [2] When the encryption key change timing is in the middle of encrypting the intra-frame encoded image, the encryption processing means may determine that the encryption key is in the middle of encrypting the intra-frame encoded image. The encryption recording device according to claim 1, wherein the encryption key change timing is delayed so as not to be changed.  [3] The input unit has a data identification unit that detects an intra-frame encoded image from the input encoded data, and changes a state of an identification flag according to the detection of the intra-frame encoded image. 3. The encryption recording device according to claim 2, wherein the encryption processing means determines whether to delay the encryption key change timing based on a state of the identification flag.  [4] The data identification unit sets the identification flag during a period from the time when the head of the intra-frame encoded image is detected to the time when the head of the encoded image different from the intra-frame encoded image is detected. 4. The encryption recording device according to claim 3, wherein a change of the encryption key is prohibited. [5] When the encryption key change timing is in the middle of encrypting the encoding unit, the input unit performs encoding so that the encryption key is not changed during encryption of the encoding unit. Make no sense right before the unit!暗 The information according to claim 1, wherein information is inserted. Encryption recording device.  [6] In an encryption recording method of encoding encoded data composed of encoding units including at least an intra-frame encoded image in a predetermined encryption unit while changing an encryption key, and recording the encrypted data, An encryption recording method, wherein at least one intra-frame encoded image is encrypted with a single encryption key so that an encryption key is not changed during encryption of the intra-frame encoded image.  [7] When the encryption key change timing is in the middle of encrypting the intra-frame encoded image, the encryption key change is performed so that the encryption key is not changed during the encryption of the intra-frame encoded image. 7. The method according to claim 6, wherein the timing is delayed.  [8] When the encryption key change timing is in the middle of encrypting the code unit, it has no meaning immediately before the coding unit so that the encryption key is not changed in the middle of encrypting the code unit. 7. The recording method according to claim 6, wherein information is inserted.