JP2008141368A - Encryption device, data distributor, and data storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an encryption device, a data distributor, and a data storage device capable of increasing hardness in attack and security without enormously increasing processing cost. <P>SOLUTION: A key generation part 12 for generating encryption keys C<SB>1</SB>to C<SB>N</SB>used for encrypting encryption text data Y for the number of destinations of the encryption text data is provided. A dual encryption text data generation part 13 having a function for performing encryption processing easier than the encryption processing at an encryption part 11 encrypts the encryption text data Y generated by the encryption part 11 by using the encryption keys C<SB>1</SB>to C<SB>N</SB>for the number of destinations generated by the key generation part 11 to generate the dual encryption text data Z<SB>1</SB>to Z<SB>N</SB>for the number of destinations from the encryption text data Y. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is an encryption device that encrypts plaintext data and generates ciphertext data from the plaintext data, a data distribution device that distributes ciphertext data generated by the encryption device, and an encryption device. The present invention relates to a data storage device that stores encrypted text data.

Any data can be copied in large numbers through distribution via a communication path or recording on a storage medium.
Even if the data is copied as described above, if the data is encrypted, the plaintext data will not be leaked immediately. However, in the unlikely event, the decryption key used to cancel the encryption of the data If data leakage or encryption compromise occurs, it becomes easy to obtain plaintext data, which is not preferable from the viewpoint of security.

Therefore, every time the encryption device distributes or records data, if the ciphertext data is re-encrypted, even if it is the same plaintext data, different ciphertext data is generated each time, making the attack difficult. Therefore, it is considered that safety is improved (for example, see Patent Document 1).
However, when the encryption device performs double encryption, it requires a large processing cost, so it is difficult to mount it on a server that distributes data to a large number of clients or small devices with limited capabilities. is there.

JP 2002-314525 A (paragraph numbers [0012] to [0021], FIG. 1)

  Since the conventional encryption apparatus is configured as described above, if the ciphertext data is re-encrypted every time data is distributed or recorded, the difficulty and security of the attack can be improved. However, since data encryption processing is expensive, it is practically difficult to perform double encryption processing, and it is difficult to sufficiently increase the difficulty and security of attacks. was there.

  The present invention has been made in order to solve the above-described problems, and an encryption device, a data distribution device, and data storage that can increase the difficulty and security of an attack without causing a large increase in processing cost. The object is to obtain a device.

  The encryption device according to the present invention is provided with key generation means for generating encryption keys used for encryption of ciphertext data for the number of destinations of the ciphertext data, and is simpler than the encryption processing in the encryption means. The double ciphertext data generation means having a function of executing the encryption process encrypts the ciphertext data generated by the encryption means using the encryption keys for the number of destinations generated by the key generation means, Double ciphertext data corresponding to the number of destinations is generated from the ciphertext data.

  According to the present invention, the key generation means for generating the encryption key used for the encryption of the ciphertext data is provided for the number of destinations of the ciphertext data, and the encryption process simpler than the encryption process in the encryption means is provided. The double ciphertext data generation means having a function to execute encrypts the ciphertext data generated by the encryption means using the encryption keys for the number of destinations generated by the key generation means, and the ciphertext Since the double ciphertext data corresponding to the number of destinations is generated from the data, there is an effect that it is possible to increase the difficulty and security of the attack without causing a large increase in processing cost.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a data distribution apparatus according to Embodiment 1 of the present invention.
Data distribution apparatus 1 encrypts the plaintext data X, implements the encryption device 1 for generating a double encrypted data Z ₁ to Z _N from the plaintext data X, the data distribution apparatus, distributing the subject In addition to the plaintext data X which is the contents of the encrypted data, an encryption key A used for encryption of the plaintext data X and a decryption key B (decryption key used for decryption) corresponding to the encryption key A input.

In the figure, the encryption unit 11 of the encryption device 1 has a function of executing advanced encryption processing such as AES (Advanced Encryption Standard), DES (Data Encryption Standard), and RSA (Rivest Shamir Adleman). Then, the plaintext data X is encrypted using the input encryption key A, and the process of generating the ciphertext data Y from the plaintext data X is performed. The encryption unit 11 constitutes an encryption unit.
When there are N destinations of the ciphertext data, the key generation unit 12 of the encryption device 1 generates N encryption keys C _{1 to} C _N used for encryption of the ciphertext data, and the encryption key A process of generating _N decryption keys D _{1 to} D _N corresponding to C _{1 to} C _N is performed. The key generation unit 12 constitutes a key generation unit.

The double ciphertext data generation unit 13 of the encryption device 1 has a function of executing a simpler encryption process than the encryption process in the encryption unit 11, and the encryption keys C ₁ to C ₁ generated by the key generation unit 12. Using C _N , the ciphertext data Y generated by the encryption unit 11 is encrypted, and N double ciphertext data Z _{1 to} Z _N are generated from the ciphertext data Y. That is, the double ciphertext data generation unit 13 performs encryption that calculates the exclusive OR of the encryption keys C _{1 to} C _N generated by the key generation unit 12 and the ciphertext data Y generated by the encryption unit 11. A process is executed to generate _N double ciphertext data Z _{1 to} Z _N from the ciphertext data Y. The double ciphertext data generation unit 13 constitutes a double ciphertext data generation unit.

The data distribution unit 14 receives the input decryption key B, the N decryption keys D _{1 to} D _N generated by the key generation unit 12, and the N duplex keys generated by the double ciphertext data generation unit 13. A process for distributing the ciphertext data Z _{1 to} Z _N to each destination is performed. The data distribution unit 14 constitutes a data distribution unit.
FIG. 2 is a flowchart showing the processing contents of the data distribution apparatus according to Embodiment 1 of the present invention.

Next, the operation will be described.
In the first embodiment, an example in which double encrypted content is distributed to N locations will be described. Note that the content may be generated in real time such as a live image or live audio in addition to a still image or a document.
First, in addition to the plaintext data X that is the content to be distributed, the data distribution apparatus includes an encryption key A used for encrypting the plaintext data X and a decryption key B (encryption key) corresponding to the encryption key A. (Decryption key used for deregistration) is input.

When the plaintext data X and the encryption key A are input, the encryption unit 11 of the encryption device 1 executes advanced encryption processing such as AES, for example.
That is, the encryption unit 11 generates ciphertext data Y from the plaintext data X by encrypting the plaintext data X using the encryption key A in a high-level encryption process such as AES (Step S1). ST1).

When the key generation unit 12 of the encryption device 1 receives information indicating that there are N content destinations from the data distribution unit 14, the key generation unit 12 uses N pieces of ciphertext data Y generated by the encryption unit 11 for encryption. It generates the encryption key C ₁ -C _N of generates N decryption key D ₁ to D _N that correspond to the encryption key C ₁ -C _N (step ST2).
However, in the first embodiment, the encryption key C _n and the decryption key D _n generated by the key generation unit 12 are the same key, and N encryption keys C _n (= D _n ) are mutually connected. It shall be generated randomly so as to be different.
“N” in the above C _n and D _n is a variable indicating any of n = 1, 2, 3,.

The double ciphertext data generation unit 13 of the encryption device 1 encrypts when the encryption unit 11 generates ciphertext data Y and the key generation unit 12 generates N encryption keys C _{1 to} C _N. An encryption process simpler than the encryption process in the unit 11 is executed.
That is, the double ciphertext data generation unit 13 performs exclusive OR of the _N encryption keys C _{1 to} C _N generated by the key generation unit 12 and the ciphertext data Y generated by the encryption unit 11. By executing a simple encryption process, N double ciphertext data Z _{1 to} Z _N are generated from the ciphertext data Y (step ST3).

Here, the double encrypted data generation unit 13, when calculating the exclusive OR of the encrypted data Y and encryption key C _n, when the data length of the ciphertext data Y is longer than the encryption key C _n Then, the length of the encryption key C _n is set as a block length, and the ciphertext data Y is divided into blocks.
Then, the exclusive OR of the entire ciphertext data Y is obtained by calculating the exclusive OR of the individual blocks and the encryption key C _n .
On the other hand, when the data length of the ciphertext data Y is shorter than the encryption key C _n or when the exclusive OR operation is performed on the final block in the exclusive OR operation for each block, the encryption Exclusive OR is performed with the upper bits of the number of encryption keys equal to the data length of the sentence data Y or the final block length.

When the double ciphertext data generation unit 13 generates N pieces of double ciphertext data Z _{1 to} Z _N , for example, the data distribution unit 14 uses the Internet to input the decryption key B and the key The N decryption keys D _{1 to} D _N generated by the generation unit 12 and the N double ciphertext data Z _{1 to} Z _N generated by the double ciphertext data generation unit 13 are used as destinations. Distribute (step ST4).
That is, the data distribution section 14, for example, for a client (1) is a destination, the decryption key B, a decryption key D _1, to deliver a double encrypted data Z _1, is the destination for the client (2), a decoding key B, a decryption key D _2, delivers a double encrypted data Z _2.
Further, the decryption key B, the decryption key _DN, and the double ciphertext data Z _N are distributed to the client (N) that is the destination.

Here, the data distribution unit 14 using the Internet, but a double encrypted data Z _n such as previously mentioned distributed to each destination, using other communication network such as ISDN or PSTN, double the encrypted data Z _n, or the like may be delivered to each destination.
In addition, various means such as transmission through a data link and distribution through a recording medium can be used regardless of wired or wireless, not limited to a communication network.

As is apparent from the above, according to the first embodiment, the key generation unit 12 that generates the encryption keys C _{1 to} C _N used for encrypting the ciphertext data Y is equal to the number of ciphertext data destinations. Provided, and a double ciphertext data generation unit 13 having a function of executing a simpler encryption process than the encryption process in the encryption unit 11 includes encryption keys C ₁ to C as many as the number of destinations generated by the key generation unit 11. with C _N, it encrypts the encrypted data Y generated by the encryption unit 11, and configured to generate the ciphertext data Y number destinations from a fraction double encrypted data Z ₁ to Z _N Therefore, there is an effect that it is possible to increase the difficulty and safety of the attack without causing a large increase in processing cost.

That is, a simple encryption process is performed for calculating the exclusive OR of the _N encryption keys C _{1 to} C _N generated by the key generation unit 12 and the ciphertext data Y generated by the encryption unit 11. As a result, N double ciphertext data Z _{1 to} Z _N are generated from the ciphertext data Y, so that the processing load of the encryption device 1 is not increased (a process for executing a high-level encryption process). Only the encryption unit 11 is required), and double encryption can be performed, and the effect of improving the difficulty and security of the attack can be achieved.

In the first embodiment, the case where the double ciphertext data generation unit 13 calculates an exclusive OR as a simple encryption process is described. However, if the simple encryption process is used, an exclusive OR is performed. However, the present invention is not limited to this calculation, and other encryption processing may be performed.
However, when using asymmetric encryption, it is necessary for the key generation unit 12 to generate the encryption keys C _{1 to} C _N and the decryption keys D _{1 to} D _N in a combination that is effective in the encryption method. is there.

In the first embodiment, the encryption unit 11 encrypts the plaintext data X using the encryption key A. However, the encryption key A may be changed periodically. However, when there is a suspicion that the encryption key A is leaked, the encryption key A may be changed.
If the encryption key A is periodically changed, security can be improved.

In the first embodiment, when the key generation unit 12 of the encryption device 1 receives the information that the number of content destinations is N from the data distribution unit 14, the ciphertext data Y generated by the encryption unit 11 is received. thereby generating N encryption key C ₁ -C _N used for encryption, shown for those generating N decryption key D ₁ to D _N that correspond to the encryption key C ₁ -C _N However, when the destination of content is added from the data distribution unit 14 and, for example, information indicating that the number of destinations of content is N + M is received, the ciphertext data Y generated by the encryption unit 11 is used for encryption. generates the N + M number of encryption keys C ₁ -C N + _M, so as to generate the encrypted key C ₁ -C N + N + M number corresponding to the _M of the decryption key D ₁ to D N + _M To do.

In the first embodiment, the key generation unit 12 of the encryption device 1 generates the encryption keys C _{1 to} C _N used for encryption of the ciphertext data Y by the number of ciphertext data destinations. However, when ciphertext data related to the same plaintext data X as the previous time is transmitted again to the same destination, an encryption key C and a decryption key D different from the previous time may be generated.

Embodiment 2. FIG.
FIG. 3 is a block diagram showing a data storage apparatus according to Embodiment 2 of the present invention.
The data storage device of FIG. 3 is equipped with an encryption device 2 that acquires ciphertext data Y that has already been encrypted and generates double ciphertext data Z _{1 to} Z _N from the ciphertext data Y. In addition to the ciphertext data Y that is the content to be distributed, the data storage device inputs a decryption key B that is used to decrypt the ciphertext data Y.

The data acquisition unit 21 of the encryption device 2 receives, for example, a scrambled broadcast, thereby acquiring the ciphertext data Y that is the scrambled broadcast data, and decrypting the ciphertext data Y for decryption. A process of acquiring the key B is performed. The data acquisition unit 21 constitutes a data acquisition unit.
Here, it is assumed that the ciphertext data Y acquired by the data acquisition unit 21 has been subjected to advanced encryption processing such as AES, DES, and RSA.

The key generation unit 22 of the encryption device 2 generates N encryption keys C _{1 to} C _N used for encryption of the ciphertext data Y when there are N storage locations of the ciphertext data, and the encryption A process of generating _N decryption keys D _{1 to} D _N corresponding to the keys C _{1 to} C _N is performed. The key generator 22 constitutes a key generator.
The double ciphertext data generation unit 23 of the encryption device 2 has a function of executing a simpler encryption process than the encryption process related to the ciphertext data Y acquired by the data acquisition unit 21. Using the generated encryption keys C _{1 to} C _N , the ciphertext data Y acquired by the data acquisition unit 21 is encrypted, and N double ciphertext data Z _{1 to} Z are encrypted from the ciphertext data Y. Implement the process to generate _N. That is, the double ciphertext data generation unit 23 performs encryption that calculates the exclusive OR of the encryption keys C _{1 to} C _N generated by the key generation unit 22 and the ciphertext data Y acquired by the data acquisition unit 21. A process is executed to generate _N double ciphertext data Z _{1 to} Z _N from the ciphertext data Y. The double ciphertext data generation unit 23 constitutes a double ciphertext data generation unit.

The double ciphertext data storage unit 24-n (n = 1, 2, 3,..., N) is a recording device such as a hard disk or a DVD recorder. The double ciphertext data Z _n is recorded.
The decryption key storage unit 25-n (n = 1, 2, 3,..., N) may be a recording device such as a hard disk or a DVD recorder. The decryption key D _n generated by the key generation unit 22 is preferably recorded.
The mapping management unit 26 records that the decryption key B and the decryption key of the ciphertext data Y acquired by the data acquisition unit 21 are the decryption key B, and N pieces of double ciphertext data Z ₁ to Z ₁ . The double ciphertext data storage units 24-1 to 24-N in which Z _N is recorded and the decryption key storage unit 25-1 in which _N decryption keys D _{1 to DN} are recorded The process which manages -25-N is implemented.
The double ciphertext data storage unit 24-n, the decryption key storage unit 25-n, and the mapping management unit 26 constitute data storage means.
FIG. 4 is a flowchart showing the processing contents of the data storage device according to the second embodiment of the present invention.

Next, the operation will be described.
In this second embodiment, an example in which doubly encrypted content is stored in N locations will be described. The content may be, for example, a text file acquired by reading a storage medium, a streaming distribution video such as IP multicast, a content file such as a unicast video or music.
First, in addition to the encrypted ciphertext data Y that is the content to be stored, a decryption key B that is used for decrypting the ciphertext data Y is input to the data storage device.

The data acquisition unit 21 of the encryption device 2 acquires, for example, ciphertext data Y that is scrambled broadcast data by receiving a scrambled broadcast, and uses the ciphertext data Y for decryption. The decryption key B is acquired (step ST11).
The ciphertext data Y acquired by the data acquisition unit 21 is subjected to advanced encryption processing such as AES, DES, and RSA, for example.

The key generation unit 22 of the encryption device 2 uses N pieces of data used for encryption of the ciphertext data Y acquired by the data acquisition unit 21 when there are N storage destinations (for example, a hard disk or a DVD recorder). It generates the encryption key C ₁ -C _N of generates N decryption key D ₁ to D _N that correspond to the encryption key C ₁ -C _N (step ST12).
However, in the second embodiment, the encryption key C _n and the decryption key D _n generated by the key generation unit 22 are the same key, and N encryption keys C _n (= D _n ) are mutually connected. It shall be generated randomly so as to be different.

When the data acquisition unit 21 acquires the ciphertext data Y and the key generation unit 22 generates N encryption keys C _{1 to} C _N , the double ciphertext data generation unit 23 of the encryption device 2 performs the encryption. An encryption process simpler than the encryption process related to the sentence data Y is executed.
That is, the double ciphertext data generation unit 23 performs exclusive OR of the _N encryption keys C _{1 to} C _N generated by the key generation unit 22 and the ciphertext data Y acquired by the data acquisition unit 21. By executing a simple encryption process, N double ciphertext data Z _{1 to} Z _N are generated from the ciphertext data Y (step ST13).

Here, the double encrypted data generation unit 23, when calculating the exclusive OR of the encrypted data Y and encryption key C _n, when the data length of the ciphertext data Y is longer than the encryption key C _n Then, the length of the encryption key C _n is set as a block length, and the ciphertext data Y is divided into blocks.
Then, the exclusive OR of the entire ciphertext data Y is obtained by calculating the exclusive OR of the individual blocks and the encryption key C _n .
On the other hand, when the data length of the ciphertext data Y is shorter than the encryption key C _n or when the exclusive OR operation is performed on the final block in the exclusive OR operation for each block, the encryption Exclusive OR is performed with the upper bits of the number of encryption keys equal to the data length of the sentence data Y or the final block length.

Double encrypted data storage unit 24-n, when the double encrypted data generation unit 23 generates a double encrypted data Z _n, records the double encrypted data Z _n (step ST14).
That is, for example, double-encrypted data storage unit 24-1 records a double encrypted data Z _1, double encrypted data storage unit 24-2 records a double encrypted data Z _2. Further, the double encrypted data storage unit 24-N records a double encrypted data Z _N.
When the key generation unit 22 generates the decryption key D _n , the decryption key storage unit 25-n records the decryption key D _n (step ST15).
Thus, for example, the decryption key storage unit 25-1 records the decryption key D _1, the decryption key storage unit 25-2 records the decryption key D _2. Further, decryption key storage unit 25-N records a decryption key D _N.

The mapping management unit 26 records that the decryption key B and the decryption key of the ciphertext data Y acquired by the data acquisition unit 21 are the decryption key B, and N double ciphertext data Z _1. -Z _N and the storage destinations of _N decryption keys D ₁ -D _N are managed (step ST16).
That is, the mapping management unit 26 manages the double ciphertext data storage units 24-1 to 24-N in which N pieces of double ciphertext data Z _{1 to} Z _N are recorded, and N decryptions. key D ₁ to D _N to manage the decryption key storing unit 25-1 to 25-N recorded.

  Thereby, for example, even if a hard disk constituting the double ciphertext data storage unit 24 is newly connected or the hard disk is replaced, the same double ciphertext data as the other hard disks is stored in the hard disk. Z is not recorded, and the decryption key storage unit 25 is a non-removable embedded internal recording device, so that the hard disk constituting the double ciphertext data storage unit 24 can be Even when connected to an encryption device or a data storage device, the double ciphertext data Z recorded on the hard disk is not analyzed.

As is apparent from the above, according to the second embodiment, the key generation unit 22 that generates the encryption keys C _{1 to} C _N used for encryption of the ciphertext data Y by the number of stored ciphertext data is provided. Provided, and a double ciphertext data generation unit 23 having a function of executing a simpler encryption process than the encryption process related to the ciphertext data Y includes the encryption keys C corresponding to the number of storages generated by the key generation unit 21. using ₁ -C _N, the encrypted data Y obtained by the data obtaining unit 21 encrypts, so as to generate the number saved from encrypted data Y fraction double encrypted data Z ₁ to Z _N Since it comprised, there exists an effect which can raise the difficulty and safety | security of an attack, without causing the increase in a big processing cost.

That is, a simple encryption process is performed to calculate the exclusive OR of the _N encryption keys C _{1 to} C _N generated by the key generation unit 22 and the ciphertext data Y acquired by the data acquisition unit 21. Thus, N pieces of double ciphertext data Z _{1 to} Z _N are generated from the ciphertext data Y, so that the processing load of the encryption device 2 is not increased (a process for executing a high-level encryption process). Part does not exist in the encryption device 2), and it becomes possible to perform double encryption, and there is an effect that it is possible to increase the difficulty and security of the attack.

In the second embodiment, the double ciphertext data generation unit 23 calculates the exclusive OR as a simple encryption process. However, if the simple encryption process is used, the exclusive OR is performed. However, the present invention is not limited to this calculation, and other encryption processing may be performed.
However, when using asymmetric encryption, it is necessary for the key generation unit 22 to generate the encryption keys C _{1 to} C _N and the decryption keys D _{1 to} D _N in a combination that is valid for the encryption method. is there.

  In the second embodiment, the double ciphertext data storage unit 24 and the decryption key storage unit 25 are hard disks and DVD recorders. However, the present invention is not limited to hard disks and DVD recorders. A storage device such as a storage medium or a magnetic storage medium may be used.

It is a block diagram which shows the data delivery apparatus by Embodiment 1 of this invention. It is a flowchart which shows the processing content of the data delivery apparatus by Embodiment 1 of this invention. It is a block diagram which shows the data storage device by Embodiment 2 of this invention. It is a flowchart which shows the processing content of the data storage device by Embodiment 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Encryption apparatus, 2 Encryption apparatus, 11 Encryption part (encryption means), 12 Key generation part (key generation means), 13 Double ciphertext data generation part (double ciphertext data generation means), 14 Data Distribution unit (data distribution unit), 21 data acquisition unit (data acquisition unit), 22 key generation unit (key generation unit), 23 double ciphertext data generation unit (double ciphertext data generation unit), 24-n 2 Double ciphertext data storage unit (data storage unit), 25-n decryption key storage unit (data storage unit), 26 mapping management unit (data storage unit).

Claims (7)

  Encryption means for encrypting plaintext data using the input encryption key and generating ciphertext data from the plaintext data, and encryption used for encrypting the ciphertext data by the number of ciphertext data destinations A key generation means for generating an encryption key, and a function for executing an encryption process simpler than the encryption process in the encryption means, and using the encryption keys for the number of destinations generated by the key generation means An encryption device comprising: double ciphertext data generation means for encrypting ciphertext data generated by the encryption means and generating double ciphertext data for the number of destinations from the ciphertext data.   Data acquisition means for acquiring ciphertext data, key generation means for generating encryption keys to be used for encryption of the ciphertext data for the number of destinations where the ciphertext data is stored, and the ciphertext acquired by the data acquisition means The encryption processing unit has a function of executing a simpler encryption process than the encryption process for sentence data, and uses the encryption keys for the number of storage destinations generated by the key generation unit to obtain the encryption acquired by the data acquisition unit. An encryption device comprising: double ciphertext data generation means for encrypting text data and generating double ciphertext data for the number of storage destinations from the ciphertext data.   The double ciphertext data generation means executes encryption processing for calculating an exclusive OR of the encryption key generated by the key generation means and the ciphertext data, and converts the double ciphertext data from the ciphertext data. The encryption device according to claim 1 or 2, wherein the encryption device is generated.   Encryption means for encrypting plaintext data using the input encryption key and generating ciphertext data from the plaintext data, and encryption used for encrypting the ciphertext data by the number of ciphertext data destinations A key generation unit that generates a decryption key corresponding to the encryption key, and a function that executes a simpler encryption process than the encryption process in the encryption unit, The ciphertext data generated by the encryption means is encrypted using the encryption keys for the number of destinations generated by the means, and double ciphertext data for the number of destinations is generated from the ciphertext data. Generated by the double ciphertext data generation means, the decryption key corresponding to the encryption key input to the encryption means, the decryption key generated by the key generation means, and the double ciphertext data generation means two Data distribution apparatus and a data distribution means for distributing the encrypted data to each destination.   The double ciphertext data generation means executes encryption processing for calculating an exclusive OR of the encryption key generated by the key generation means and the ciphertext data generated by the encryption means, and the ciphertext data 5. The data distribution apparatus according to claim 4, wherein double ciphertext data is generated from the data.   Data acquisition means for acquiring ciphertext data and acquiring a decryption key used for decrypting the ciphertext data, and ciphertext data used for encrypting the ciphertext data corresponding to the number of ciphertext data storage destinations An encryption key is generated, and a key generation unit that generates a decryption key corresponding to the encryption key and an encryption process that is simpler than the encryption process related to the ciphertext data acquired by the data acquisition unit And encrypts the ciphertext data acquired by the data acquisition unit using the encryption keys for the number of storage destinations generated by the key generation unit, and the number of storage destinations from the ciphertext data. The double ciphertext data generating means for generating the double ciphertext data, the decryption key acquired by the data acquisition means, the decryption key generated by the key generation means and the double ciphertext data Data storage apparatus and a data storage means for storing a double encrypted data generated by the formation means.   The double ciphertext data generation means executes an encryption process for calculating an exclusive OR of the encryption key generated by the key generation means and the ciphertext data acquired by the data acquisition means, and the ciphertext data 7. The data storage device according to claim 6, wherein double ciphertext data is generated from the data.

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