JP5395449B2 - Security system, information recording apparatus, security method, and program - Google Patents

Description

  The present invention relates to a technique for concealing data, and more particularly to a technique for encrypting data and storing it in an information recording medium and managing access to the data.

  An information recording apparatus such as a digital camera, a video camera, or a digital IC recorder includes an information recording medium therein, and stores data collected by photographing or the like in the information recording medium. When such an information recording device is lost or stolen, not only the information recording device itself is damaged, but also the information stored in the information recording medium leaks, and a great deal of damage may occur.

  In order to avoid such a problem, the information recording apparatus manages the access authority to the information recording medium using a password or the like so that only the authorized person can read the data stored in the information recording medium. (For example, refer nonpatent literature 1).

  In addition, like some music players, when data stored in an information recording medium is uniformly encrypted and the data is read from the information recording medium, authentication processing is performed on the determined software and the authentication is successful. There is also a technique for restricting unintended access by decrypting data only in

“Security function to protect important information with a password”, [online], Panasonic Corporation, [searched on January 20, 2009], Internet <http://panasonic.jp/icrec/us470/security.html>

  However, in recent information recording apparatuses such as digital cameras, removable information recording media such as CF cards, SD cards, memory sticks, and DVD media are often used as information recording media. In this case, even if the information recording device manages the access authority to the information recording medium using a password or the like, the information recording medium is removed from the information recording device, and the management of the access authority by the information recording device If it does not reach the medium, there is a problem that anyone can access the data stored in the information recording medium.

  On the other hand, by uniformly encrypting data to be stored in the information recording medium, when reading data from the information recording medium, by performing authentication processing on the determined software and decrypting the data only when the authentication is successful, There is no such problem in the case of a method that restricts unintended access. However, in this method, it is necessary to share secret information such as a password and a key necessary for executing the authentication process in advance with each information processing apparatus. In this case, a complicated process of distributing / setting secret information to be shared to each information processing apparatus is required. Therefore, in this method, the advantage of the removable information recording medium that data can be easily transferred to various information processing apparatuses is lost.

  The present invention has been made in view of the above points, and without causing each information processing apparatus to share secret information, the information recording medium is stored in the information recording medium even in an environment where the information recording medium is removed from the information recording apparatus. The purpose is to provide a technology that can manage the access of data.

  In the present invention, the information processing device PC (i) stores the secret key SK (i) of the public key cryptosystem corresponding to the information processing device PC (i). Each secret key SK (i) corresponds to each information processing device PC (i) itself, and there is no need to perform complicated processing such as distributing and setting secret information to a plurality of devices.

  The information recording device RE (j) generates a common key KA of the common key encryption method, generates a ciphertext SE (KA, M) obtained by encrypting the data M using the common key KA, and generates each secret key SK ( Using the public keys PK (i) corresponding to i) respectively, the ciphertext PE (PK (i), KA) is generated by encrypting the common key KA, and the ciphertext SE (KA, M) and ciphertext PE (PK (i), KA) is stored in the information recording medium. Since the ciphertext SE (KA, M) and the ciphertext PE (PK (i), KA) are ciphertext, even in an environment where the information recording medium is removed from the information recording device RE (j), the information recording medium Manage access to stored data.

  The information processing apparatus PC (i) that reads the data M decrypts the ciphertext PE (PK (i), KA) stored in the information recording medium by using the secret key SK (i) corresponding to the data M itself, and KA is generated, and using this common key KA, the ciphertext SE (KA, M) stored in the information recording medium is decrypted to generate data M.

  As described above, according to the present invention, access to data stored in an information recording medium can be managed even in an environment where the information recording medium is removed from the information recording apparatus without causing each information processing apparatus to share secret information. .

FIG. 1 is a block diagram for explaining the overall configuration of the security system according to the first embodiment. FIG. 2 is a block diagram for explaining a functional configuration of the information processing apparatus 11-i (i = 1,..., N, n ≧ 1) in FIG. FIG. 3 is a block diagram for explaining a functional configuration of the information recording apparatus of FIG. FIG. 4 is a block diagram for explaining a functional configuration of the information recording medium of FIG. FIG. 5A is a sequence diagram for explaining the initial registration process of the first embodiment. FIG. 5B is a sequence diagram for explaining the data reading process of the first embodiment. FIG. 6 is a sequence diagram for explaining the data writing process of the first embodiment. FIG. 7 is a block diagram for explaining a functional configuration of the information processing apparatus 21-i (i = 1,..., N, n ≧ 1) according to the second embodiment. FIG. 8 is a block diagram for explaining a functional configuration of the information recording apparatus of the second embodiment. FIG. 9 is a block diagram for explaining a functional configuration of the information recording medium 23 of the second embodiment. FIG. 10 is a sequence diagram for explaining the data writing process of the second embodiment. FIG. 11 is a sequence diagram for explaining the common key update processing of the second embodiment. FIG. 12 is a sequence diagram for explaining the data reading process of the second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, a first embodiment of the present invention will be described.

<Configuration>
FIG. 1 is a block diagram for explaining the overall configuration of the security system 1 of the first embodiment. FIG. 2 is a block diagram for explaining a functional configuration of the information processing apparatus 11-i (i = 1,..., N, n ≧ 1) in FIG. FIG. 3 is a block diagram for explaining a functional configuration of the information recording apparatus 12 of FIG. FIG. 4 is a block diagram for explaining a functional configuration of the information recording medium 13 of FIG.

  As shown in FIG. 1, the security system 1 of the present embodiment includes n information processing devices 11-i (corresponding to the information processing device PC (i)) and an information recording device 12 (information recording device RE (j) ( j = 1,..., u, u = 1)) and the information recording medium 13.

  As shown in FIG. 2, the information processing apparatus 11-i of the present embodiment includes a control unit 11a-i, a temporary memory 11b-i, a storage unit 11c-i, a key pair generation unit 11d-i, a writing unit 11e-i, It includes an output unit 11f-i, an input unit 11g-i, a reading unit 11h-i, a key decryption unit 11i-i, a data decryption unit 11j-i, and a decode unit 11k-i.

  The information processing apparatus 11-i of this embodiment is, for example, a known computer having a central processing unit (CPU), an auxiliary storage device, a random-access memory (RAM), a read-only memory (ROM), and an input / output interface. A predetermined program is read and configured. That is, the control unit 11a-i, the key pair generation unit 11d-i, the key decryption unit 11i-i, the data decryption unit 11j-i, and the decode unit 11k-i, for example, have a predetermined program executed by the CPU. It is a processing part comprised by these. The temporary memory 11b-i and the storage unit 11c-i are storage areas including, for example, an auxiliary storage device, a RAM, a cache memory, and the like. The writing unit 11e-i and the reading unit 11h-i are, for example, read / write devices that write data to a recording area and read data from a storage area. The output unit 11f-i and the input unit 11g-i are, for example, an input / output interface that exchanges data with an external device or a read / write device that exchanges data with an external recording medium. The information processing apparatus 11-i executes each process under the control of the control unit 11a-i. Unless otherwise specified, the data output from each processing unit is stored in the temporary memory 11b-i one by one, and the data stored in the temporary memory 11b-i is read from another processing unit as necessary. Used for processing.

  As shown in FIG. 3, the information recording apparatus 12 of this embodiment includes a control unit 12a, a temporary memory 12b, a storage unit 12c, an input unit 12d, an output unit 12e, a writing unit 12f, a data acquisition unit 12g, an encoding unit 12h, and a reduction unit. A data generation unit 12i, a common key generation unit 12j, a data encryption unit 12k, a reading unit 12m, a key encryption unit 12n, and a display unit 12p are included.

  The information recording apparatus 12 of this embodiment is, for example, a digital camera, a video camera, a digital IC recorder, and the like. Each function of the information recording apparatus 12 is configured by reading a predetermined program into a known computer. That is, the control unit 12a, the encoding unit 12h, the reduced data generation unit 12i, the common key generation unit 12j, the data encryption unit 12k, and the key encryption unit 12n are processes configured by a predetermined program being executed by the CPU. Part. The temporary memory 12b and the storage unit 12c are storage areas including, for example, an auxiliary storage device, a RAM, a cache memory, and the like. The writing unit 12f and the reading unit 12m are, for example, read / write devices that write data to a recording area and read data from a storage area. The input unit 12d and the output unit 12e are, for example, an input / output interface that exchanges data with an external device or a read / write device that exchanges data with an external recording medium. The data acquisition unit 12g is a device such as a camera, a microphone, and an input interface to which data is input. The display unit 12p is a liquid crystal panel, a speaker, or the like.

  The information recording apparatus 12 executes each process under the control of the control unit 12a. Unless otherwise specified, the data output from each processing unit is stored in the temporary memory 12b one by one, and the data stored in the temporary memory 12b is read from another processing unit as necessary and used for processing. Is done.

  As shown in FIG. 4, the information recording medium 13 of this embodiment has a storage unit 13a. The information recording medium 13 may be, for example, a removable information recording medium such as a CF card, an SD card, a memory stick, a DVD medium, or a non-removable information recording medium built in the information recording device 12. Good.

<Initial registration process>
First, the initial registration process necessary for using this system will be described.
FIG. 5A is a sequence diagram for explaining the initial registration process of the first embodiment.

  The first registration process is executed independently by each information processing apparatus 11-i constituting this system. First, the key pair generation unit 11d-i of the information processing apparatus 11-i generates a key pair composed of a public key cryptosystem secret key SK (i) and a public key PK (i) (step S101). Specific examples of the public key cryptosystem include RSA and ID-based cryptography, but it is desirable to use a public key cryptosystem that has a smaller computation cost for the encryption computation than the computation cost for the decryption computation. The generated secret key SK (i) is stored in the storage unit 11c-i by the writing unit 11e (step S102). The generated public key PK (i) is output from the output unit 11f-i and input to the input unit 12d of the information recording device 12. The public key PK (i) is stored in the storage unit 12c from the writing unit 12f (step S103).

  By the initial registration process, the secret keys SK (i) corresponding to the respective information processing apparatuses 11-i are stored in the respective storage units 11c-i, and the public keys PK (i) of all the information processing apparatuses 11-i are stored. It is stored in the storage unit 12 c of the information recording device 12.

<Data writing process>
Next, a data writing process in which the information recording device 12 stores data in the information recording medium 13 will be described.
FIG. 6 is a sequence diagram for explaining the data writing process of the first embodiment.

  First, data D is input to the data acquisition unit 12g of the information recording device 12 (FIG. 3) (step S111). This process corresponds to, for example, image shooting, voice input, and the like. The input data D is input to the encoding unit 12h, and the encoding unit 12h encodes the encoded data D to generate encoded data M (step S112).

  The data M is input to the reduced data generation unit 12i, and the reduced data generation unit 12i generates reduced data S that is data related to the data M and has a smaller amount of information than the data M (step S113). Specific examples of the reduced data S are only thumbnails with reduced image quality of data D, mosaic images of data D, attribute information such as the date / time and file name of data D, whether or not shooting or recording was performed. Information indicating The generated reduced data S is stored in the storage unit 12c from the writing unit 12f. The reduced data S is used for confirming an outline of stored data in the information recording device 12. By storing the reduced data S in the storage unit 12c of the information recording device 12 in this way, it is possible to ensure a higher level of safety than when the reduced data S is stored in the storage unit 13a of the information recording medium 13.

  Further, the common key generation unit 12j generates a common key KA of a common key cryptosystem such as AES or Camellia (step S114). For example, the common key generation unit 12j uses a random number having a predetermined bit length as the common key KA. The generated common key KA is input to the data encryption unit 12k, and the data M output from the encoding unit 12h is further input to the data encryption unit 12k. The data encryption unit 12k generates a ciphertext SE (KA, M) obtained by encrypting the data M using the common key KA (step S115). The generated common key KA is also input to the key encryption unit 12n. Further, the reading unit 12m reads each public key PK (i) from the storage unit 12c and sends it to the key encryption unit 12n. The key encryption unit 12n uses each public key PK (i) to generate a ciphertext PE (PK (i), KA) obtained by encrypting the common key KA (step S116).

  The ciphertext SE (KA, M) generated in step S115 and each ciphertext PE (PK (i), KA) generated in step S116 are sent to the output unit 12e, and the output unit 12e The information is stored in the storage unit 13a of the information recording medium 13 (step S117).

<Data reading process>
A data reading process in which the information processing apparatus 11-i reads data from the information recording medium 13 will be described.
FIG. 5B is a sequence diagram for explaining the data reading process of the first embodiment.

  First, the input unit 11g-i of the information processing apparatus 11-i (FIG. 2) receives the ciphertext SE (KA, M) and the ciphertext PE (PK (i), KA) from the storage unit 13a of the information recording medium 13. And the writing unit 11e-i stores them in the storage unit 11c-i (step S131).

  Next, the reading unit 11h-i reads the ciphertext PE (PK (i), KA) and the secret key SK (i) from the storage unit 11c-i, and these are input to the key decryption unit 11i-i. . The key decryption unit 11i-i decrypts the ciphertext PE (PK (i), KA) using the secret key SK (i) and generates a common key KA (step S132). The generated common key KA is input to the data decryption unit 11j-i. Further, the reading unit 11h-i reads the ciphertext SE (KA, M) from the storage unit 11c-i and sends it to the data decryption unit 11j-i. The data decryption unit 11j-i decrypts the ciphertext SE (KA, M) using the common key KA and generates data M (step S133).

  The generated data M is input to the decoding unit 11k-i, where it is decoded (decoded) into data D and output (step S134).

<Display processing>
The information recording device 12 can output a public key PK (i) registered for the first time and a list of stored reduced data S. In this case, the reading unit 12m reads the public key PK (i) and the reduced data S from the storage unit 12c, and the display unit 12p outputs them.

[Features of this embodiment]
The ciphertext SE (KA, M) and the ciphertext PE (PK (i), KA) are stored in the information recording medium 13, and the data M can be decrypted from these ciphertexts. Only the information processing apparatuses 11-i that hold the key SK (i). That is, the information processing apparatus that has not performed the initial registration process cannot acquire the data M from the information recording medium 13. Thereby, even in an environment in which the information recording medium 13 is removed from the information recording device 12, access to the data M stored in the information recording medium 13 can be managed.

  In addition, it is the own secret key SK (i) that each information processing apparatus 11-i of this embodiment needs to register in advance. Therefore, complicated processing such as when a plurality of information processing apparatuses share common secret information is unnecessary.

  Further, the public key encryption operation performed by the information recording apparatus 12 of this embodiment is only an encryption operation, and there is no need to perform a decryption operation. By using a public key cryptosystem in which the computation cost of the encryption computation is smaller than the computation cost of the decryption computation, the computation cost to be executed by the information recording device 12 can be reduced. Therefore, even when the information recording apparatus 12 is not so high in calculation capability as a digital camera or the like, the present system can be executed at high speed.

  The present invention is not limited to the embodiment described above. For example, in the present embodiment, a case where only one information recording device 12 exists has been described, but a plurality of information recording devices 12 (information recording devices RE (j) (j = 1,..., U, u> 1 ) May be present. In this embodiment, the reduced data S and the public key PK (i) are stored in the storage unit 12c of the information recording device 12. However, the public key PK (i) is stored in the storage unit 13a of the information recording medium 13, and the information recording device 12 reads the public key PK (i) from the storage unit 13a of the information recording medium 13 and uses it. Also good. As a result, when there are a plurality of information recording devices 12, it is not necessary to execute the initial registration process for each information recording device 12. In this embodiment, the reduced data S is stored in the storage unit 12c of the information recording device 12. However, the reduced data S may be stored in the storage unit 13a of the information recording medium 13, and the information recording device 12 may read and use the reduced data S from the storage unit 13a of the information recording medium 13. As a result, when there are a plurality of information recording devices 12, the reduced data S generated by one information recording device 12 can be used by another information recording device 12.

  Further, the reduced data S may not be generated, and the data D acquired by the data acquisition unit 12g without encoding may be used as the data M. In this case, decoding is also unnecessary.

  In this embodiment, the key pair of the public key cryptosystem is generated at the time of the initial registration process. However, the initial registration is performed using the key pair of the public key cryptosystem set before the initial registration process. Processing may be performed.

  In addition, the various processes described above are not only executed in time series according to the description, but may be executed in parallel or individually according to the processing capability of the apparatus that executes the processes or as necessary. Needless to say, other modifications are possible without departing from the spirit of the present invention.

[Second Embodiment]
This embodiment is a modification of the first embodiment, in which the information recording device 12 updates the common key. Below, it demonstrates centering around difference with 1st Embodiment.

<Configuration>
FIG. 7 is a block diagram for explaining a functional configuration of the information processing apparatus 21-i (i = 1,..., N, n ≧ 1) according to the second embodiment. FIG. 8 is a block diagram for explaining a functional configuration of the information recording apparatus 22 of the second embodiment. FIG. 9 is a block diagram for explaining a functional configuration of the information recording medium 23 of the second embodiment. In these drawings, the same reference numerals as those used in the first embodiment are used for portions common to the first embodiment, and the description is simplified.

  In the security system of the present embodiment, the information processing device 11-i of the security system 1 of the first embodiment is replaced with the information processing device 21-i, the information recording device 12 is replaced with the information recording device 22, and the information recording medium 13 Is replaced with the information recording medium 23.

  As shown in FIG. 7, the information processing apparatus 21-i of this embodiment includes a control unit 11a-i, a temporary memory 11b-i, a storage unit 11c-i, a key pair generation unit 11d-i, a writing unit 11e-i, It has an output unit 11f-i, an input unit 11g-i, a reading unit 11h-i, a key decryption unit 21i-i, a data decryption unit 21j-i, and a decode unit 11k-i.

  The information processing apparatus 21-i of this embodiment is configured, for example, by loading a predetermined program into a known computer. For example, the key decryption unit 21i-i and the data decryption unit 21j-i are processing units configured by a predetermined program being executed by the CPU.

  As shown in FIG. 8, the information recording device 22 of this embodiment includes a control unit 12a, a temporary memory 12b, a storage unit 12c, an input unit 12d, an output unit 12e, a writing unit 12f, a data acquisition unit 12g, an encoding unit 12h, and a reduction. The data generation unit 12i, the common key generation unit 22j, the data encryption unit 22k, the reading unit 12m, the key encryption unit 22n, and the display unit 12p are included.

  The information recording device 22 of this embodiment is, for example, a digital camera, a video camera, a digital IC recorder, and the like. Each function of the information recording device 22 is configured by reading a predetermined program into a known computer. For example, the common key generation unit 22j, the data encryption unit 22k, and the key encryption unit 22n are processing units configured by a predetermined program being executed by the CPU.

  As shown in FIG. 9, the information recording medium 23 of this embodiment includes a storage unit 23a. The information recording medium 23 may be a removable information recording medium such as a CF card, an SD card, a memory stick, or a DVD medium, or may be a non-removable information recording medium built in the information recording device 22. Good.

<Initial registration process>
Since it is the same as 1st Embodiment, description is abbreviate | omitted.

<Data writing process>
Next, a data writing process in which the information recording device 22 stores data in the information recording medium 23 will be described.
FIG. 10 is a sequence diagram for explaining the data writing process of the second embodiment.

  First, data D is input to the data acquisition unit 12g of the information recording device 22 (FIG. 8) (step S211). Next, the controller 12a sets k = 0 and stores k in the temporary memory 12b (step S211). The data D is input to the encoding unit 12h, and the encoding unit 12h encodes (encodes) the input data D to generate encoded data M (k) = M (0) (step S212).

  The data M (k) is input to the reduced data generation unit 12i, and the reduced data generation unit 12i is data related to the data M (k) and has a smaller amount of information than the data M (k). Is generated (step S213). The generated reduced data S is stored in the storage unit 12c from the writing unit 12f.

  Further, the common key generation unit 22j generates a common key KA (k) of a common key cryptosystem such as AES or Camellia (step S214). Common key generation unit 22j For example, a random number having a predetermined bit length is set as a common key KA (k). The generated common key KA (k) is input to the data encryption unit 22k, and the data M (k) output from the encoding unit 12h is further input to the data encryption unit 22k. The data encryption unit 22k generates a ciphertext SE (KA (k), M (k)) obtained by encrypting the data M (k) using the common key KA (k) (step S215). The generated common key KA (k) is also input to the key encryption unit 22n. Also, the reading unit 12m reads each public key PK (i) from the storage unit 12c and sends it to the key encryption unit 22n. The key encryption unit 22n generates a ciphertext PE (PK (i), KA (k)) obtained by encrypting the common key KA (k) using each public key PK (i) (step S216). .

  The ciphertext SE (KA (k), M (k)) generated in step S215 and each ciphertext PE (PK (i), KA (k)) generated in step S216 are sent to the output unit 12e. The output unit 12e stores them in the storage unit 23a of the information recording medium 23 (step S217).

<Common key update processing>
Next, a common key update process in which the information recording device 22 updates the common key KA (k) will be described. The update of the common key KA may be performed, for example, every time the data D is input to the data acquisition unit 12g, or is performed whenever the information recording device 22 that is in the power-off state is turned on. Also good. In the former case, the safety is further increased, and in the latter case, the number of operations of the information recording device 22 can be reduced.
FIG. 11 is a sequence diagram for explaining the common key update processing of the second embodiment.

When updating the common key KA (k), first, the control unit 12a stores k + 1 as a new k in the temporary memory 12b (step S221). Next, the common key generation unit 22j generates a new common key KA (k) (step S222). For example, the common key generation unit 22j uses a random number having a predetermined bit length as the common key KA (k). The generated common key KA (k) is input to the data encryption unit 22k. Further, the input unit 12d reads the ciphertext SE (KA (k-1), M (k-1)) from the storage unit 23a of the information recording medium 23. The ciphertext SE (KA (k-1), M (k-1)) is input to the data encryption unit 22k as new data M (k). The data encryption unit 22k encrypts new data M (k) using a new common key KA (k) (corresponding to KA _new ) and creates a new ciphertext SE (KA (k), M (k) ) Is generated (step S223).

  The new common key KA (k) is also input to the key encryption unit 22n. Also, the reading unit 12m reads each public key PK (i) from the storage unit 12c and sends it to the key encryption unit 22n. The key encryption unit 22n generates a new ciphertext PE (PK (i), KA (k)) obtained by encrypting each new common key KA (k) using each public key PK (i). (Step S224).

  The new ciphertext SE (KA (k), M (k)) generated in step S223 and the new ciphertext PE (PK (i), KA (k)) generated in step S224 are output. The output unit 12e stores these in the storage unit 23a of the information recording medium 23 (step S225). At this time, in order to prevent decryption with the common key KA (k-1) before the update, the ciphertext SE (KA (k-1), M (k- 1)) is preferably deleted from the storage unit 23a of the information recording medium 23.

<Data reading process>
A data reading process in which the information processing apparatus 21-i reads data from the information recording medium 23 will be described.
FIG. 12 is a sequence diagram for explaining the data reading process of the second embodiment.

  First, the input unit 11g-i of the information processing device 21-i (FIG. 7) reads the ciphertext SE (KA (k), M (k)) from the storage unit 23a of the information recording medium 23, and writes the writing unit 11e-. i stores this in the storage unit 11c-i (step S231). The input unit 11g-i reads the ciphertext PE (PK (i), KA (k)) from the storage unit 23a of the information recording medium 23, and the writing unit 11e-i stores it in the storage unit 11c-i. (Step S232).

  Next, the reading unit 11h-i reads the ciphertext PE (PK (i), KA (k)) and the secret key SK (i) from the storage unit 11c-i, and these read them to the key decryption unit 21i-i. Entered. The key decryption unit 21i-i decrypts the ciphertext PE (PK (i), KA (k)) using the secret key SK (i) and generates a common key KA (k) (step S233). The generated common key KA (k) is input to the data decryption unit 21j-i. Further, the reading unit 11h-i reads the ciphertext SE (KA (k), M (k)) from the storage unit 11c-i and sends it to the data decryption unit 21j-i. The data decryption unit 21j-i decrypts the ciphertext SE (KA (k), M (k)) using the common key KA (k), and generates data M (k) (step S234). Here, when k = 0 is not satisfied, M (k) = SE (KA (k−1), M (k−1)).

  Next, the control unit 11a-i determines whether or not k = 0 (step S235). If k = 0, k-1 is set as a new k, and the data SE (KA generated in step S234 is displayed. The process returns to step S232 with (k-1), M (k-1)) as the new ciphertext SE (KA (k), M (k)). On the other hand, if k = 0, the data M (k) = M (0) is input to the decoding unit 11k-i, where it is decoded (decoded) into data D and output (step S237).

<Display processing>
The same as in the first embodiment.

[Features of this embodiment]
The ciphertext SE (KA (k), M (k)) and ciphertext PE (PK (i), KA (k)) are stored in the information recording medium 23, and data M is obtained from these ciphertexts. (k) can be decrypted only by each information processing device 21-i that holds its own secret key SK (i). That is, an information processing apparatus that has not performed the initial registration process cannot acquire data M (k) from the information recording medium 23. Thereby, even in an environment in which the information recording medium 23 is removed from the information recording device 22, access to the data M (k) stored in the information recording medium 23 can be managed.

  In addition, it is the private key SK (i) that each information processing apparatus 21-i of this embodiment needs to register in advance. Therefore, complicated processing such as when a plurality of information processing apparatuses share common secret information is unnecessary.

  In this embodiment, since the information recording device 22 updates the common key KA (k), the safety can be further improved. For example, an attacker's device that has already acquired the pre-update common key KA (k-1) but has not acquired the post-update common key KA (k) The ciphertext SE (KA (k), M (k)) encrypted with can not be decrypted. Each time the common key KA (k) is updated, the ciphertext SE (KA (k-1), M (k-1)) corresponding to the common key KA (k-1) before the update is stored in the information recording medium 23. If it is deleted from, safety is further improved.

  Further, the public key encryption operation performed by the information recording apparatus 22 of this embodiment is only an encryption operation, and there is no need to perform a decryption operation. By using a public key cryptosystem in which the calculation cost of the encryption calculation is smaller than the calculation cost of the decryption calculation, the calculation cost to be executed by the information recording device 22 can be reduced. Therefore, even when the information recording device 22 is not so high in calculation capability as a digital camera or the like, the present system can be executed at high speed.

  The present invention is not limited to the embodiment described above. For example, in the present embodiment, a case has been described in which only one information recording device 22 exists, but a plurality of information recording devices 22 (information recording devices RE (j) (j = 1,..., U, u> 1 ) May be present. In this embodiment, the reduced data S and the public key PK (i) are stored in the storage unit 12c of the information recording device 22. However, the public key PK (i) is stored in the storage unit 23a of the information recording medium 23, and the information recording device 22 reads and uses the public key PK (i) from the storage unit 23a of the information recording medium 23. Also good. As a result, when there are a plurality of information recording devices 22, it is not necessary to perform the initial registration process for each information recording device 22. In this embodiment, the reduced data S is stored in the storage unit 12c of the information recording device 22. However, the reduced data S may be stored in the storage unit 23a of the information recording medium 23, and the information recording device 22 may read and use the reduced data S from the storage unit 23a of the information recording medium 23. As a result, when there are a plurality of information recording devices 22, the reduced data S generated by one information recording device 22 can be used by another information recording device 22.

  Further, the reduced data S may not be generated, or the data D acquired by the data acquisition unit 22g without encoding may be used as the data M (0). In this case, decoding is also unnecessary.

  In this embodiment, the key pair of the public key cryptosystem is generated at the time of the initial registration process. However, the initial registration is performed using the key pair of the public key cryptosystem set before the initial registration process. Processing may be performed.

  In addition, the various processes described above are not only executed in time series according to the description, but may be executed in parallel or individually according to the processing capability of the apparatus that executes the processes or as necessary. Needless to say, other modifications are possible without departing from the spirit of the present invention.

[Programs]
When the above configuration is realized by a computer, the processing contents of the functions that each device should have are described by a program. The processing functions are realized on the computer by executing the program on the computer.

  The program describing the processing contents can be recorded on a computer-readable recording medium. As the computer-readable recording medium, for example, any recording medium such as a magnetic recording device, an optical disk, a magneto-optical recording medium, and a semiconductor memory may be used.

  The program is distributed by selling, transferring, or lending a portable recording medium such as a DVD or CD-ROM in which the program is recorded. Furthermore, the program may be distributed by storing the program in a storage device of the server computer and transferring the program from the server computer to another computer via a network.

  A computer that executes such a program first stores, for example, a program recorded on a portable recording medium or a program transferred from a server computer in its own storage device. When executing the process, the computer reads a program stored in its own recording medium and executes a process according to the read program. As another execution form of the program, the computer may directly read the program from a portable recording medium and execute processing according to the program, and the program is transferred from the server computer to the computer. Each time, the processing according to the received program may be executed sequentially. Also, the program is not transferred from the server computer to the computer, and the above-described processing is executed by a so-called ASP (Application Service Provider) type service that realizes the processing function only by the execution instruction and result acquisition. It is good. Note that the program in this embodiment includes information that is used for processing by an electronic computer and that conforms to the program (data that is not a direct command to the computer but has a property that defines the processing of the computer).

  In this embodiment, the present apparatus is configured by executing a predetermined program on a computer. However, at least a part of these processing contents may be realized by hardware.

  Examples of the industrial application field of the present invention include digital cameras, video cameras, digital IC recorders, and the like.

DESCRIPTION OF SYMBOLS 1 Security system 11, 21 Information processing apparatus 12, 22 Information recording apparatus 13, 23 Information recording medium

Claims (6)

n (n ≧ 1) information processing devices PC (i) (i = 1,..., n) and u (u ≧ 1) information recording devices RE (j) (j = 1,... ., u) and an information recording medium,
The information processing device PC (i) includes a storage unit that stores a secret key SK (i) of a public key cryptosystem corresponding to the information processing device PC (i),
The information recording device RE (j)
A common key generation unit that generates a common key KA of the common key cryptosystem;
A data encryption unit that generates a ciphertext SE (KA, M) obtained by encrypting the data M using the common key KA;
A public key PK (i) respectively corresponding to the secret key SK (i), and a key encryption unit for generating ciphertext PE (PK (i), KA) obtained by encrypting the common key KA,
A writing unit for storing the ciphertext SE (KA, M) and the ciphertext PE (PK (i), KA) in the information recording medium,
The information processing apparatus PC (i)
Using a secret key SK (i) corresponding to itself, decrypting the ciphertext PE (PK (i), KA) stored in the information recording medium, and generating the common key KA, and
A data decryption unit that decrypts the ciphertext SE (KA, M) stored in the information recording medium using the common key KA, and generates the data M;
When the common key is updated after the ciphertext SE (KA, M) is stored in the information recording medium,
The common key generation unit generates a new common key KA of the common key cryptosystem,
The data encryption unit sets the ciphertext SE (KA, M) as new data M, and a new ciphertext SE (KA, M) obtained by encrypting the new data M using the new common key KA. )
The key encryption unit uses a public key PK (i) corresponding to the secret key SK (i), respectively, and encrypts the new common key KA. KA),
The writing unit stores the new ciphertext SE (KA, M) and the new ciphertext PE (PK (i), KA) in the information recording medium, and updates the new data M. Deleting the previous ciphertext SE (KA, M) from the information recording medium;
Security system characterized by that. The security system of claim 1,
The information recording device RE (j)
A reduced data generation unit that generates reduced data S that is related to the data M and has a smaller amount of information than the data M;
The reduced data S is
Stored in at least one storage unit of the information recording device RE (j) or the information recording medium,
Security system characterized by that. The security system according to claim 1 or 2,
The public key cryptosystem is a scheme in which the operation cost of the encryption operation is smaller than the operation cost of the decryption operation.
Security system characterized by that. A common key generation unit that generates a common key KA of the common key cryptosystem;
A data encryption unit that generates a ciphertext SE (KA, M) obtained by encrypting the data M using the common key KA;
Using public key PK corresponding respectively to the secret key SK (i): (i) respectively, said common key KA each encrypted ciphertext PE (PK (i), KA) and a key encrypting unit for generating,
A writing unit for storing the ciphertext SE (KA, M) and the ciphertext PE (PK (i), KA ) and into the information recording medium,
Have
When the common key is updated after the ciphertext SE (KA, M) is stored in the information recording medium,
The common key generation unit generates a new common key KA of the common key cryptosystem,
The data encryption unit sets the ciphertext SE (KA, M) as new data M, and a new ciphertext SE (KA, M) obtained by encrypting the new data M using the new common key KA. )
The key encryption unit uses a public key PK (i) corresponding to the secret key SK (i), respectively, and encrypts the new common key KA. KA),
The writing unit stores the new ciphertext SE (KA, M) and the new ciphertext PE (PK (i), KA) in the information recording medium, and updates the new data M. Deleting the previous ciphertext SE (KA, M) from the information recording medium;
An information recording apparatus characterized by that. n (n ≧ 1) information processing devices PC (i) (i = 1,..., n) and u (u ≧ 1) information recording devices RE (j) (j = 1,... ., u) and an information recording medium,
The storage unit of the information processing device PC (i) stores a secret key SK (i) of a public key cryptosystem corresponding to the information processing device PC (i),
The information recording device RE (j) generating a common key KA of a common key cryptosystem;
The information recording device RE (j) generates a ciphertext SE (KA, M) obtained by encrypting the data M using the common key KA;
The information recording device RE (j) uses a public key PK (i) corresponding to the secret key SK (i), respectively, and encrypts the common key KA, respectively, and encrypts the encrypted text PE (PK (i), KA )
The information recording device RE (j) storing the ciphertext SE (KA, M) and the ciphertext PE (PK (i), KA) in the information recording medium;
The information processing device PC (i) decrypts the ciphertext PE (PK (i), KA) stored in the information recording medium using a secret key SK (i) corresponding to the information processing device PC (i), and the common key Generating KA; and
The information processing apparatus PC (i) uses the common key KA to decrypt the ciphertext SE (KA, M) stored in the information recording medium and generate the data M;
Run
When the common key is updated after the ciphertext SE (KA, M) is stored in the information recording medium,
The information recording device RE (j) generating a new common key KA of a common key cryptosystem;
The information recording device RE (j) sets the ciphertext SE (KA, M) as new data M, and encrypts the new data M using the new common key KA. KA, M), and
The information recording device RE (j) uses a public key PK (i) corresponding to the secret key SK (i), respectively, and encrypts the new common key KA, respectively. i), KA), and
The information recording device RE (j) stores the new ciphertext SE (KA, M) and the new ciphertext PE (PK (i), KA) in the information recording medium, and the new data Deleting the ciphertext SE (KA, M) before being updated as M from the information recording medium;
Security method to perform.   A program for causing a computer to function as the information recording apparatus according to claim 4.

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