JP2009124456A - Information processor, information processing method, information processing program, and information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a code in which different encryption levels are mixed into a code which can be normally decrypted. <P>SOLUTION: The MPU 402 of a computer 401 reads image data, performs encryption processing to the image data to be converted into code data to be encrypted. Next, the MPU 402 divides the code data to be encrypted into blocks, encrypts the divided code data by an encryption key 1 and an encryption key 2 to generate the encrypted encryption data 701. After that, the MPU 402 reads the encryption data of a code sequence which irregularly changes, encrypted by the encryption key 1 and the encryption key 2, generates encryption data 702 in which the read encryption data is aligned for each piece of encryption key 1 and the encryption key 2, and prevents pieces of code data which can be restored by different encryption keys from being alternately produced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image data encryption process, and more particularly to an information processing apparatus, an information processing method, an information processing program, and an information recording medium that generate encrypted data that can be restored using different encryption keys.

  In recent years, various information such as character data, image data, and voice data has been digitized due to the rapid development and spread of computers and their networks. Digital information is not deteriorated due to aging, etc., and can be stored indefinitely. However, digital information can be easily copied, and copyright protection is a big problem. Therefore, security technology for copyright protection is rapidly gaining importance.

  One technology that protects copyright is cryptographic technology. In particular, as an encryption method for digital content such as image data, a common key encryption method (also called a secret key encryption method, a symmetric encryption method, a conventional encryption method) in which the same encryption key is secretly shared between the sender and the receiver is used. is there. For example, as shown in Non-Patent Document 1, the common key cryptosystem is a block cipher that encrypts a character string (block) of an appropriate length with the same key and a stream that changes the key for each character string or bit. Can be divided into ciphers. Among block ciphers, DES (Date Encryption Standard) and AES (Advanced Encryption Standard) are well known. As the stream cipher, for example, as shown in Non-Patent Document 1, a business cipher using multiple tables, a Burnham cipher using a one-time disposable key, and the like are known.

  Therefore, copyright protection by encrypting the entire image data can be easily realized by using one of the common key cryptosystems. In other words, the encryption key is shared between the sender and the receiver, and the receiver can decrypt the image data encrypted by the sender using the key.

  On the other hand, as one method of high-efficiency encoding for compressing image data, the JPEG method recommended by ISO and ITU-T is widely used as an international standard encoding method for still images. This JPEG method is based on discrete cosine transform, but there is a problem in that block-like distortion occurs when the compression rate is increased. Therefore, as shown in Non-Patent Document 2, there is an encoding method that uses a discrete wavelet transform as a transform method different from the previous discrete cosine transform in order to achieve a higher resolution of an image and a higher compression rate. It has been proposed and is now standardized as JPEG2000.

  FIG. 1 is a block diagram of a JPEG2000 encoder. The input image is first decomposed into subbands corresponding to the resolution level by discrete wavelet transform (DWT) (101), and then quantized (102). FIG. 2 shows an example of subband decomposition when the decomposition level is 2 (resolution level number 3), and there are resolution levels from level 0 to level 2. FIG. At this time, a coefficient belonging to a smaller resolution level includes lower frequency information. The quantized wavelet coefficients are encoded by the EBCOT algorithm. In the following, this algorithm is divided into five parts: code block division (103), coefficient modeling (104), arithmetic coding (105) and rate control (106), layer formation (107), and packet generation (108). explain.

(1) Code block division Each subband is divided into square blocks (eg, 64 × 64) called code blocks. These code blocks are encoded independently.
(2) Coefficient modeling Coefficient modeling based on the pit plane is performed for the wavelet coefficient sequence of each code block. Thus, an embedded code string in which coefficient bits are arranged in order of importance is generated. All bit planes from the MSB to the LSB are decomposed into three sub-bit planes (paths) depending on the context. The boundary of each sub-bit brain is called a truncation point, and becomes the minimum division unit when data is discarded later.
(3) Arithmetic coding and rate control Adaptive arithmetic coding is performed on the embedded code string generated by coefficient modeling. Thereafter, the target bit rate is obtained by appropriately truncating the arithmetic code string with the truncation point that is the boundary of the sub-bit brain as a unit.
(4) Layer formation When it is necessary to sequentially display with a plurality of image quality, that is, when SNR scalable is necessary, code layer formation is performed next. Each layer includes a part of the embedded code of each code block. The higher the layer, the more important components are included in image reproduction.
(5) Packet generation Each layer is decomposed into units called bodies, and header information is added to each layer to generate a packet. Here, each body has information of the corresponding resolution level. Therefore, the total number of packets generated is the product of the number of layers and the number of resolution levels. The header information includes information such as the length of the arithmetic code string of each code block and the number of sub-bit brains. As shown in FIG. 3, the final JPEG2000 code string is obtained by putting all packets 0 to K together and adding global header information. However, JPEG2000 stipulates that the above-described various header information and sub-bit plane, which is the minimum unit of data division, have a size that is an integral multiple of 1 byte.
Ikeno and Koyama, “Contemporary Cryptography”, The Institute of Electronics, Information and Communication Engineers, 1986. Chapter 2 and Chapter 4 Final version of JPSEC FDIS, ISO IEC / JTC 1 / SC 29 / WG 1 / wg1n3853, 2006. Section B.5.4 of Chapter B

  As described above, digital image data has a security problem, and it is required to encrypt the image data. Further, when one image data is disclosed to a plurality of viewers, there is an increasing demand for changing the disclosed image for each user, not only in the two stages of disclosure and non-disclosure.

  Since JPEG2000 can be decrypted independently for each packet, it is possible to construct code data that can be encrypted in stages according to the accessible level and disclosed for each access level, and can respond to the previous request. Is possible. For example, only a level 0 in FIG. 2 can be disclosed to a certain user, and a level 1 can be disclosed to a certain user.

  However, when a code encrypted in a chained encryption method such as CBC (Cipher Block Chaining), CFB (Cipher Feedback), or OFB (Output Feedback) is used, the display result is as expected. A situation that does not occur occurs.

  The JPEG2000 code has a high degree of freedom in order arrangement of packets classified by parameters such as image position, resolution, color component, and layer. In the code formation situation, a code that can be restored with a different encryption key is included in the code. It will occur alternately.

  However, when a decryption processing device that can process only an encrypted code that can be restored with a specific encryption key encounters a code that cannot be processed, the subsequent code processing becomes difficult, and the code that can be processed thereafter Cannot be obtained, and the expected result cannot be obtained.

  An object of the present invention is to provide an information processing apparatus, an information processing method, an information processing program, and an information recording medium in which such a problem is solved and a code in which different encryption levels are mixed can be normally decoded. It is what.

  An information processing apparatus according to the present invention is an information processing apparatus that divides image data into rectangular areas and encrypts code data that is independently compressed for each divided rectangular area, and the dividing means that divides the code data And encryption key setting means for setting at least two types of encryption keys, and the code data divided by the dividing means can be decrypted with at least two types of encryption keys set by the encryption key setting means Encryption means for converting into encrypted data, and alignment means for aligning the encrypted data of the code data in the same rectangular area encrypted by the encryption means for each encryption key.

  A second information processing apparatus according to the present invention is an information processing apparatus for encrypting image data, wherein the image data is divided into rectangular areas, and code data is generated by compressing each divided rectangular area independently. Encoding means, dividing means for dividing the code data generated by the encoding means, encryption key setting means for setting at least two types of encryption keys, and code data divided by the dividing means, Encryption means for converting into encrypted data that can be decrypted with at least two types of encryption keys set by the encryption key setting means, and encryption of code data in the same rectangular area encrypted by the encryption means Alignment means for aligning the data for each encryption key.

  The alignment means may align the encrypted data encrypted by the encryption means for each encryption key.

  The arranging unit may arrange the encrypted data encrypted with different encryption keys by the encrypting unit into an arrangement accessible independently.

  Furthermore, the alignment means may align the encrypted data of the code data of different rectangular areas encrypted by the encryption means for each encryption key.

  The arranging unit may arrange the encrypted data encrypted by the encrypting unit in order of encryption level.

  The code data encrypted by the information processing apparatus is JPEG2000 code data.

  An information processing method according to the present invention is an information processing method for dividing image data into rectangular areas, and encrypting code data that has been independently compressed for each divided rectangular area, the step of dividing the code data; A step of setting at least two types of encryption keys, a step of converting the divided code data into encrypted data that can be decrypted by at least two types of set encryption keys, and the encrypted data And arranging the encrypted data of the code data in the same rectangular area for each encryption key.

  According to a second information processing method of the present invention, image data is divided into rectangular areas, each of the divided rectangular areas is compressed independently to generate code data, and the generated code data is divided. A step of setting at least two types of encryption keys, a step of converting the divided code data into encrypted data that can be decrypted by the set at least two types of encryption keys, and the same encrypted rectangular area And arranging the encrypted data of the encoded data for each encryption key.

  In the aligning step, the encrypted encrypted data may be aligned for each encryption key.

  In the aligning step, the encrypted data encrypted with different encryption keys may be aligned in an independently accessible arrangement.

  Further, in the aligning step, the encrypted data of the code data of different rectangular areas may be aligned for each encryption key.

  Further, in the arranging step, the encrypted encrypted data may be arranged in order of encryption level.

  Code data to be encrypted by the information processing method is JPEG 2000 code data.

  An information processing program according to the present invention causes a computer that processes image data to execute each of the information processing methods.

  An information recording medium according to the present invention is characterized in that a computer-readable program is recorded in order to cause a computer that processes image data to execute each of the information processing methods.

  The present invention divides image data into rectangular areas, divides the code data generated by independently compressing each divided rectangular area, encrypts it with at least two types of encryption keys, and converts it into encrypted data Since the converted encrypted data is arranged for each encryption key, code data that can be recovered with different encryption keys is not generated alternately. Even a decoding processing apparatus capable of processing only data can reliably restore image data and obtain a desired image.

  FIG. 4 is a block diagram showing the basic configuration of the information processing apparatus (computer) of the present invention. The computer 401 can input an image read from the scanner 417, and can edit and store the image. In addition, an image obtained by the scanner 417 can be printed by the printer 416. Various instructions and the like from the user are performed by input operations of the mouse 413 and the keyboard 14. Inside the computer 401, each block is connected by a bus 407, and various data can be transferred.

  The MPU 402 is connected to each block in the computer 401 via the bus 407, and controls the operation of each block or executes a program stored therein. The main storage device 403 temporarily stores programs and image data to be processed for processing performed in the MPU 402. A hard disk (HDD) 404 stores programs and image data to be transferred to the main storage device 403 in advance, and stores processed image data. A scanner interface (I / F) 415 is connected to the scanner 417 and inputs image data obtained by the scanner 417. The printer interface 408 is connected to the printer 416 and transmits print image data to the printer 416. A CD drive 409 reads or writes data stored in a CD (CD-R / CD-RW) which is one of external storage media. The DVD drive 410 reads from or writes to a DVD, which is one of external storage media. The FDD drive 411 reads from and writes to the FDD which is one of the external storage media. If an image editing program, an encryption processing program, or a printer driver is stored in an external storage medium such as a CD, DVD, or FDD, these programs are installed on the HDD 404, and main memory is stored as necessary. The data is transferred to the device 403. An interface (I / F) 412 receives an input instruction from the mouse 413 or the keyboard 414. The video controller 405 transmits display data to the monitor 406. A monitor 406 displays various information and processing processes. The video controller 405 transmits display data to the monitor 406.

  The computer 401 converts image data or compressed code data into encrypted data that can be restored with a different encryption key. As shown in the flowchart showing the processing flow of FIG. The stored original code data and the like are written into the main storage device 403 (step S501). Next, the MPU 402 reads and encrypts code data and the like from the main storage device 403 (step S502). The MPU 402 writes the encrypted data in a different area from the original code data and the like in the main storage device 403 (step S503). Thereafter, the encrypted data stored in the main storage device 403 is written in an area different from the original code data of the HDD 404 by an instruction from the MPU 402 (step S504).

  An arbitrary encryption method can be applied to the encryption processed by the computer 401, but a common key encryption method in which the same encryption key is secretly shared between the encryption side and the decryption side will be described as an example. The common key encryption method is a known method such as DES (Date Encryption Standard) or AES (Advanced Encryption Standard) that performs encryption with the same key for each character string (block) having an appropriate length.

  There are two basic operations of DES: (1) dividing data into 64-bit blocks and (2) encrypting each block with a 56-bit key. There are four modes, ECB, CB, CFB, and OFB, depending on usage.

ECB (Electronic Code Block) is a mode that can be said to be a basic type of DES, and the basic operation is performed as it is. That is, after dividing the data into blocks, each block is encrypted with a secret key, and these blocks are connected in the original order.
CBC (Cipher Block Chaining) takes an XOR (exclusive OR) of an encrypted previous block and an unencrypted current block and encrypts it with a secret key. As the term Chaining is used, the encryption of each block proceeds in a chain.
CFB (Cipher Feedback) is a mode in which a part (m bits) of the encryption result of the previous block is fed back as a value that takes an exclusive OR with m bits of the next block.
OFB (Output Feedback) generates ciphertext using a certain initial value as the first block, and uses that ciphertext or part of it as input for the next ciphertext, and at the same time supports part (m bits) as a random number. This mode takes an exclusive OR with m-bit data. By appropriately selecting m bits in the above mode, encryption for each arbitrary bit length can be realized.

  When the computer 401 divides the image data into rectangular areas by this common key encryption method, and the code data compressed independently for each divided rectangular area is converted into encrypted data that can be restored with different encryption keys. The process will be described with reference to the flowchart of FIG.

  The MPU 402 of the computer 401 reads image data (step S601), and stores the encoded data to be encoded by encoding the read image data in the main storage device 403 (step S602). The code data to be encrypted is composed of a JPEG2000 stream, for example, composed of codes with a resolution level of 3 levels, an area (precinct) division of 4, a color component 1, and an image quality (layer) division of 1. Next, the MPU 402 reads code data to be encrypted from the main storage device 403, divides the read code data into blocks (step S603), sets two types of encryption keys, and sets two types of code data divided. And the encrypted data that has been encrypted is stored in the main storage device 403 (steps S604 and S605). When code data is encrypted with these two types of encryption keys, precinct 0 and presync 1 of the JPEG 2000 stream are encrypted with encryption key 1, precinct 2 and presync 3 are encrypted with encryption key 2, and FIG. Assume that the encrypted data 701 shown in FIG. The progression order indicating the order of packets detected in the code stream is RPCL (Resolution Level-Position-Component-Layer Progression) as an example.

  In this case, as shown in FIG. 7A, the encryption key that can decrypt the encrypted data 701 is a code string that is irregularly changed. In FIG. 7, MH is a main header, TPH0 is a tile part header, RiP0 and RiP1 (i = 0 to 2) are packet data encrypted with the encryption key 1, and RiP2 and RiP3 (i = 0 to 2) are The packet data encrypted with the encryption key 2 is shown.

  The MPU 402 reads encrypted data of an irregularly changed code string encrypted with the encryption key 1 and the encryption key 2, and reads the main header of the read encrypted data (step S606). Next, the encrypted data is read up to the boundary position between the encryption key 1 and the encryption key 2, and the encrypted data of the same encryption key is temporarily stored (steps S607, S608, S609). For example, in FIG. 7A, after reading packet data R0P0 and R0P1, packet data R0P2 and R0P3 are read. The boundary position when reading this packet data is indicated by a JPSEC marker in the case of an encrypted code. In the case of an unencrypted code, it is decoded from the main header, tile part header, packet header, and the like.

  When this process is repeated until the reading of all the encrypted data is completed (step S610), the encrypted data of the encryption key 1 and the encryption key 2 are collected together as shown in FIG. Encrypted data 702 arranged for each identical encryption key is generated (step S611). Since the code data of the encryption key 1 and the code data of the encryption key 2 are continued in this way, code data that can be restored by the encryption key 1 and the encryption key 2 does not alternately occur. Even a decryption processing device that can process only the encrypted code data that can be restored in 1 can reliably restore the image data as expected.

  Alignment of the encrypted data for each encryption key 1 and encryption key 2 is realized by changing the progression order of the entire code to PCRL (Position-Component-Resolution Level-Layer Progression) in order to obtain the desired data order. To do.

  Further, when the encrypted data for each of the encryption key 1 and the encryption key 2 are arranged, the order of the packets is to be changed as shown in the encrypted data 702a in FIG. 8 without changing the progression order of the entire code data. The progression order may be temporarily changed only at the position. In this case, a POPEG (Progression order change) marker segment of JPEG2000 can be used.

  In the above description, after all the encrypted data has been read, the encrypted data of the encryption key 1 and the encryption key 2 are combined to generate encrypted data arranged for the same encryption key. As described above, as shown in FIG. 9A, the encrypted data 701 of the code string in which the encryption key that can be decrypted by being encrypted with the encryption key 1 and the encryption key 2 is irregularly changed is illustrated. As shown in FIG. 9B, the encrypted data 702b may be generated by dividing the same encryption key into tile parts. In this case, the data code of the encryption key that cannot be processed can be skipped from the code length of the tile part described in the tile part headers TPH0, TPH1, and TPH2, and either the encryption key 1 or the encryption key 2 can be skipped. Even with a decryption processing device that can process only the encrypted code data that can be restored by the above, it is possible to reliably restore the encrypted data and obtain the expected image data.

  In each of the above explanations, the case where the packet order in the tile is converted has been described. However, the encrypted data of the encoded data between the tiles can be similarly generated by dividing the data into the same encryption keys. It is also possible to generate encrypted data obtained by arranging and dividing encrypted data for each identical encryption key according to the encryption level.

  That is, as shown in FIG. 10A, encrypted data 801 obtained by encrypting code data between tiles at two different encryption levels 0 and 1 as shown in FIG. 10B. One of the encryption level 0 and the encryption level 1 is generated by generating the encrypted data 802 obtained by sorting the tiles into the encrypted data for each of the encryption levels 0 and 1 and rearranging the tiles. Even with a decryption processing apparatus that can process only the encrypted code data that can be restored by the encrypted data, the encrypted data can be reliably restored.

  In the above description, the case where the encoding process, the encryption process, and the conversion process of the encrypted data are performed simultaneously and continuously by the MPU 402 of the computer 401 has been described. However, these processes may be performed separately as necessary.

It is a block diagram which shows the structure of a JPEG2000 encoder. It is a figure which shows a subband by the discrete wavelet transform in JPEG2000. It is a schematic diagram which shows the structure of the stream of JPEG2000. It is a block diagram which shows the basic composition of the information processing apparatus of this invention. It is a flowchart which shows the encryption process by information processing apparatus. It is a flowchart which shows the encoding process of this invention, an encryption process, and the conversion process of encryption data. It is a schematic diagram which shows the encryption data which carried out the encryption process, and the encryption data which carried out the conversion process. It is a schematic diagram which shows the encryption data which performed the 2nd conversion process to encryption data. It is a schematic diagram which shows the encryption data which performed the 3rd conversion process to encryption data. It is a schematic diagram which shows the encryption data which carried out the other encryption process, and the encryption data which carried out the conversion process.

Explanation of symbols

401; Computer; 402; MPU; 403; Main storage; 404; HDD;
405; video controller, 406; monitor, 407; bus,
408; Printer I / F, 409; CD drive, 410; DVD drive,
411; FDD drive, 412; I / F, 413; mouse, 414; keyboard,
415; Scanner I / F, 416; Printer, 417; Scanner.

Claims (16)

An information processing apparatus that divides image data into rectangular areas and encrypts code data that is independently compressed for each divided rectangular area,
Dividing means for dividing the code data;
An encryption key setting means for setting at least two types of encryption keys;
Encryption means for converting the code data divided by the dividing means into encrypted data that can be decrypted by at least two types of encryption keys set by the encryption key setting means;
An alignment means for aligning the encrypted data of the code data of the same rectangular area encrypted by the encryption means for each encryption key;
An information processing apparatus comprising: An information processing apparatus for encrypting image data,
An encoding unit that divides the image data into rectangular areas, and generates code data by independently compressing each divided rectangular area;
A dividing unit for dividing the code data generated by the encoding unit;
An encryption key setting means for setting at least two types of encryption keys;
Encryption means for converting the code data divided by the dividing means into encrypted data that can be decrypted by at least two types of encryption keys set by the encryption key setting means;
An alignment means for aligning the encrypted data of the code data of the same rectangular area encrypted by the encryption means for each encryption key;
An information processing apparatus comprising:   The information processing apparatus according to claim 1, wherein the sorting unit sorts the encrypted data encrypted by the encryption unit for each encryption key.   The information processing apparatus according to claim 1, wherein the arranging unit arranges the encrypted data encrypted by the encryption unit using different encryption keys into an arrangement that can be accessed independently.   3. The information processing apparatus according to claim 1, wherein the aligning unit aligns the encrypted data of the code data of different rectangular areas encrypted by the encryption unit for each encryption key.   3. The information processing apparatus according to claim 1, wherein the sorting unit sorts the encrypted data encrypted by the encryption unit in order of encryption level.   The information processing apparatus according to claim 1, wherein the code data to be encrypted is JPEG2000 code data. An information processing method that divides image data into rectangular areas and encrypts code data that is independently compressed for each divided rectangular area,
Dividing the code data;
Setting at least two types of encryption keys;
Converting the divided code data into encrypted data that can be decrypted with at least two types of set encryption keys;
Aligning the encrypted data of the encrypted encoded data of the same rectangular area for each encryption key;
An information processing method characterized by comprising: Dividing the image data into rectangular areas, and generating code data by independently compressing each divided rectangular area;
Dividing the generated code data; and
Setting at least two types of encryption keys;
Converting the divided code data into encrypted data that can be decrypted with at least two types of set encryption keys;
Aligning encrypted data of encrypted code data of the same rectangular area for each encryption key;
An information processing apparatus comprising:   10. The information processing method according to claim 8, wherein in the arranging step, the encrypted encrypted data is arranged for each encryption key.   10. The information processing method according to claim 8 or 9, wherein in the aligning step, the encrypted data encrypted with different encryption keys are aligned in an independently accessible arrangement.   10. The information processing apparatus according to claim 8, wherein in the aligning step, the encrypted data of the code data in different rectangular areas is aligned for each encryption key.   10. The information processing method according to claim 8, wherein in the arranging step, the encrypted encrypted data are arranged in order of encryption level.   14. The information processing method according to claim 8, wherein the code data to be encrypted is JPEG2000 code data.   An information processing program that causes a computer that processes image data to execute the information processing method according to claim 8.   An information recording medium on which a computer-readable program is recorded in order to cause a computer that processes image data to execute the information processing method according to claim 8.

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