JP2013167740A - Encryption device, encryption method, and encryption program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a processing time of an encryption process by a counter mode.SOLUTION: The encryption device includes: expanded key generation means for generating an expanded key from an encryption key; information output means for retaining a first counter value, when data length of encryption data is a predetermined data length or more, outputting a first counter value and retaining a counter value formed by updating the first counter value as a second counter value, when the data length of the encryption data is less than the predetermined data length, retaining the second counter value having the same value as that of the first counter value, and outputting a counter difference between the first counter value and the second counter value that is the updated counter value or is the same value as that of the first counter value; intermediate data generation means for determining a range of intermediate data generated from the expanded key and the first counter value on the basis of the counter difference, and outputting the intermediate data; and data randomizing means for encrypting the output intermediate data using the expanded key.

Description

  The present invention relates to an encryption device, an encryption method, and an encryption program for concealing data during data communication and storage.

  A common key block cipher is a technique for concealing communication data and stored data. Currently, the block size of the proposed block cipher is 64 bits or 128 bits.

When a message longer than the block length is encrypted, the message is divided into block sizes and encryption processing is performed. At this time, a technique called an encryption usage mode is used. One of them is a counter (CTR) mode.
Encryption in CTR mode is

C ₀ = E _K (ctr) + M ₀
C ₁ = E _K (ctr + 1) + M ₁
C ₂ = E _K (ctr + 2) + M ₂
:

Done in Here, E _K is an encryption process using a key K, ctr is a counter initial value, M _i (i is 0 or a positive integer) is a message divided into block sizes, and C _i (i is 0 or a positive integer) is Indicates encrypted data. + Indicates exclusive OR (XOR).

  The counter value should not be used until the key K is changed. When the CTR mode is implemented by software implementation, the counter value is often updated by an arithmetic addition instruction. Here, attention is paid to changes in data due to arithmetic addition.

FIG. 1 shows a change in state when one is added to 4-bit binary data. The bit numbers are 0, 1, 2, and 3 in order from the right of the 4-digit numerical value. Looking at the state change of each bit when +1 is added, the nth bit changes from 0 to 1 or from 1 to 0 every 2 ⁿ times.

  As described above, in many cases, the effect of the carry in the arithmetic addition is local, and the influence of the carry is less likely to occur as the distance from the least significant bit is changed.

  In recent years, the block length of block ciphers is often 64 bits or more, and when such a block cipher is implemented in the CTR mode, the change of the input value (ctr) becomes local.

  As for the technology related to the present application, there is an encryption device disclosed in Patent Documents 1-3. Japanese Patent Application Laid-Open No. 2004-133620 discloses an encryption device including intermediate data control means for performing a change operation for changing necessary intermediate data during execution of encryption processing depending on a random number output from a random number generation device. Patent Document 2 discloses a cryptographic device to which a tamper resistant circuit is added (paragraphs 0017, 0018, etc.). Patent Document 3 discloses an encryption apparatus using a block encryption technique that performs encryption in units of blocks.

JP 2000-305453 A JP 2006-025288 A International Publication No. 2009/034929

  In the data expansion process using the block cipher, the message and the key data are agitated by repeating the round process a number of times determined by the specification. In general, each bit of a message does not spread over the entire block width in a single round process, but spreads over the entire block width by repeating multiple times.

  If the continuous message change is local like the counter value in the CTR mode, the change of the intermediate data by the round process may be local, and the calculation of the intermediate data that is clearly not changed is useless. is there. Such a case is applicable not only to the CTR mode but also to a case where the change of input data is limited to a part.

[Object of invention]
An object of the present invention is to provide an encryption device, an encryption method, and an encryption program in the case where the change of input data is local.

An encryption apparatus according to the present invention includes an extended key generation unit that generates an extended key from an encryption key;
A first counter value based on encrypted data is held, and when the data length of the encrypted data is greater than or equal to a predetermined data length, the first counter value is output and the first counter value is updated Holding the counter value as a second counter value, and holding a second counter value that is the same value as the first counter value when the data length of the encrypted data is less than a predetermined data length; Information output means for outputting a counter difference between the first counter value and the second counter value that is an updated counter value or the same as the first counter value;
Intermediate data generating means for determining a range of intermediate data generated from the extended key and the first counter value based on the counter difference, and outputting the generated intermediate data;
Data agitation means for encrypting and outputting the output intermediate data using the expanded key;
Is an encryption device.

The encryption method of the present invention generates an extended key from an encryption key,
A first counter value based on encrypted data is held, and when the data length of the encrypted data is greater than or equal to a predetermined data length, the first counter value is output and the first counter value is updated Holding the counter value as a second counter value, and holding a second counter value that is the same value as the first counter value when the data length of the encrypted data is less than a predetermined data length; Outputting a counter difference between the first counter value and the second counter value that is an updated counter value or the same as the first counter value;
Based on the counter difference, determine a range of intermediate data to be generated from the extended key and the first counter value, and output the generated intermediate data,
In the encryption method, the output intermediate data is encrypted using the extended key and output.

The encryption program of the present invention is stored in a computer as an encryption device.
A function to generate an extended key from an encryption key;
A first counter value based on encrypted data is held, and when the data length of the encrypted data is greater than or equal to a predetermined data length, the first counter value is output and the first counter value is updated Holding the counter value as a second counter value, and holding a second counter value that is the same value as the first counter value when the data length of the encrypted data is less than a predetermined data length; A function of outputting a counter difference between the first counter value and the second counter value that is an updated counter value or the same as the first counter value;
A function of determining a range of intermediate data to be generated from the extended key and the first counter value based on the counter difference, and outputting the generated intermediate data;
It is an encryption program for executing the function of encrypting and outputting the output intermediate data using the extended key.

  According to the present invention, since it is not necessary to calculate the intermediate data of the part that does not change to the counter value, the calculation time of the encryption process can be shortened.

It is a figure which shows the example of the carry in the addition of binary number data. It is a figure which shows the encryption apparatus of one Embodiment which concerns on this invention. It is a figure which shows a counter update means. It is a figure which shows an example of the data stirring means of an encryption algorithm. It is a figure which shows the processing flow of implementation of this invention. It is a figure which shows the position of intermediate data. It is a figure which shows the intermediate data updated when x1 changes.

  Next, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  Referring to FIG. 2, the encryption device 2 of this embodiment includes an extended key generation unit 20, a data agitation unit 21, an information output unit 22, an intermediate data generation unit 23, and a calculation unit 24. The calculation unit 24 may be provided outside the encryption device.

  The data agitation unit 21 and the expanded key generation unit 20 may use any encryption algorithm. Typical block cipher algorithms include AES (Advanced Encryption Standard) and DES (Data Encryption Standard).

  The information output unit 22 receives the data length (bits) of encrypted data and the counter initial value. The information output unit 22 includes a loop control unit 220, a counter update unit 221, a difference calculation unit 222, a first counter 223, a second counter 224, and a remaining data length storage unit 225.

  The data length is stored in the remaining data length storage unit 225.

  If the remaining data length stored in the remaining data length storage unit 225 is 1 bit or more, the loop control unit 220 issues an update instruction to the counter update unit 221. If the remaining data length is equal to or greater than the block length (N bits), N is output as the encrypted data length, and N is subtracted from the remaining data length stored in the remaining data length storage unit 225.

  If the remaining data length stored in the remaining data length storage unit 225 is less than N (M bits), M is output as the encrypted data length, and the remaining data length is set to zero.

  The initial counter value is stored in the counter 223. Upon receiving an update instruction from the loop control unit 220, the counter update unit 221 outputs the count value of the counter 223, increments the counter value, and stores it in the counter 224.

  The difference calculation unit 222 calculates the difference between the count value of the counter 223 and the count value of the counter 224. Here, the difference means a result of exclusive OR of the counter 223 and the counter 224. If the i-th bit (0 ≦ i ≦ N−1) of the counter 223 and the counter 224 is equal, the difference value is 0, and if they are different, the difference value is 1. After calculating the difference, the counter 223 is updated with the value of the counter 224.

A configuration example of the data agitation unit 21 will be described with reference to FIG. Input data (intermediate data) of 8n (n ≧ 3) bits is divided into eight n-bit data and processed. The F function 3 receives n-bit data and an n-bit extended key ek _ij (1 ≦ i ≦ r, 0 ≦ j ≦ 3), and stirs them to output n-bit data. The output data of the F function is exclusive-ORed with other n-bit data by the exclusive-OR circuit 4 (the symbol “+” in ◯, hereinafter referred to as XOR). The eight n-bit data after the F function processing is cyclically shifted and passed to the next round. The output data is 8n bits obtained by combining the data after r rounds.

  Next, the operation of the present embodiment will be described with reference to the flowcharts of FIGS. 2, 3, 4, and 5.

  First, the extended key generation unit 20 generates an extended key from the encryption key (step S1). In the case of the algorithm shown in FIG. 4, a 4n × r-bit extended key is generated and held in a storage device such as an internal memory. The expanded key generation method is a method defined by the employed encryption algorithm. For example, in the case of AES, a method according to Key Expansion defined by FIPS-197 can be employed.

  Next, the intermediate data generation unit 23 reads the extended key held in the storage device, and generates intermediate data from the extended key and the counter value output from the information output unit 22 (step S2).

  The intermediate data specifically generated by the intermediate data generation unit 23 will be described with reference to FIG.

  The 8n-bit counter value is divided into 8 n-bit data. Assume that x0 is lower and x7 is higher.

  Since x0 is positioned at the lowest position of the counter, it is data in which the counter value always changes.

  The bold line data path represents the path affected by x0, and the F functions 50 to 65 on the bold line path calculate each block. Since x0 affects all the 8 intermediate data of 8 round outputs, all F functions must be calculated after 9 rounds. What is held as intermediate data is (23 × n) bits of output data 500 to 522 of the F function on the thin line data path that is not affected by x0.

  The intermediate data generation unit 23 determines the intermediate data to be updated using the counter difference output from the information output unit 22. In the example of the intermediate data generation unit 23 in FIG. 6, the determination can be made by looking at the position of the most significant bit (referred to as the kth bit) where the counter difference of 1 is set. If k ≦ n−1, the intermediate data does not change, so the update process is not performed. If n ≦ k ≦ 2n−1, it means that x1 is changing. In this case, the intermediate data 500, 502, 505, 508, 510 is updated. At this time, by using the intermediate data 511, 512, and 513, the F function to be recalculated can be only 66 to 69. Further, if 2n ≦ k ≦ 3n−1, it means that x2 and x1 change. In this case, in addition to the intermediate data, the intermediate data 509, 511, 512, and 513 are updated. However, the intermediate data 509, 511, 512, and 513 are updated, and then the intermediate data 500, 502, 505, 508, and 510 are updated. At the start of the encryption process, all intermediate data is calculated by setting, for example, a value of all 1 as the counter difference.

  Next, the data length to be encrypted is set to the remaining data length (step S3).

  The encryption process repeats steps S4 to S7.

  If the remaining data length is 0, it is determined that the encryption process has been completed, and the process ends. If the remaining data length is not 0, the counter value is encrypted (step S4).

In the counter value encryption process up to eight rounds, x0 is input and the thick data path in FIG. 6 is calculated. The procedure is shown below.

1. XOR the intermediate data 500 to x0 (the result of XOR is t0).
2. t0 is agitated with the expanded key ek ₂₀ by the F function 50, and the output data of the F function 50 and the intermediate data 501 are XORed (the result of XOR is t1).
3. XOR the intermediate data 502 at t0 (the result of the XOR is t01).
4). The t1 is agitated with the expanded key ek ₃₀ by the F function 51, and the output data of the F function 51 and the intermediate data 503 are XORed (the result of XOR is t2).
5. The t01 is agitated with the expanded key ek ₄₁ by the F function 52, and the output data of the F function 52 is XORed to t1 (the result of XOR is assumed to be t11).
6). The t2 is agitated with the expanded key ek ₄₀ by the F function 53, and the output data of the F function 53 and the intermediate data 504 are XORed (the result of XOR is t3).
7). XOR the intermediate data 505 at t01 (the result of XOR is t02).
8). t11 is agitated with the expanded key ek ₅₁ by the F function 54, and the output data of the F function 54 is XORed to t2 (the result of XOR is assumed to be t21).
9. t3 is agitated with the expanded key ek ₅₀ by the F function 55, and the output data of the F function 55 and the intermediate data 506 are XORed (the result of XOR is t4).
10. t02 is agitated with the expanded key ek ₆₂ by the F function 56, and the output data of the F function 56 is XORed to t11 (the result of XOR is t12).
11. t21 is agitated with the expanded key ek ₆₁ by the F function 57, and the output data of the F function 57 is XORed to t3 (the result of XOR is t31).
12 t4 is stirred with the expanded key ek ₆₀ by the F function 58, and the output data of the F function 58 and the intermediate data 507 are XORed (the result of the XOR is t5).
13. XOR the intermediate data 508 at t02 (the result of XOR is t03).
14 t12 is agitated with the expanded key ek ₇₂ by the F function 59, and the output data of the F function 59 is XORed to t21 (the result of XOR is assumed to be t22).
15. t31 is agitated with the expanded key ek ₇₁ by the F function 60, and the output data of the F function 60 is XORed to t4 (the result of XOR is assumed to be t41).
16. t5 is agitated with the expanded key ek ₇₀ by the F function 61, and the output data of the F function 61 and the intermediate data 509 are XORed (the result of XOR is t6).
17. The t03 is stirred with the expanded key ek ₈₃ by the F function 62, and the output data of the F function 62 is XORed to t12 (the result of XOR is set to t13).
18. The t22 is stirred with the expanded key ek ₈₂ by the F function 63, and the output data of the F function 63 is XORed to t31 (the result of XOR is set to t32).
19. t41 is agitated with the expanded key ek ₈₁ by the F function 64, and the output data of the F function 64 is XORed to t5 (the result of XOR is assumed to be t51).
20. t6 is stirred with the expanded key ek ₈₀ by the F function 65, and the output data of the F function 65 and the intermediate data 510 are XORed (the result of the XOR is t7).

  Since t03, t13, t22, t32, t41, t51, t6, and t7 calculated in the above procedure become output data of 8 rounds, the remaining (r-8) uses the expanded key to calculate all F functions. I do.

  If the remaining data length is greater than or equal to the block length N, the N-bit data output from the data agitation unit is XORed into plain text. If it is less than N bits, XOR is performed only for the remaining data length.

  Then, the remaining data is updated (step S6). If the remaining data length is N bits or more, N is subtracted, and if it is less than N bits, the remaining data length is set to zero.

Next, the counter value is updated (step S7). At this time, if no carry affecting the intermediate data has occurred, the process returns to step S4 (step S8). If a carry affecting the intermediate data occurs, the intermediate data is updated (step S9).
In the encryption apparatus according to this embodiment, each unit shown in FIG. 2 is configured by hardware such as a dedicated IC. Here, two or more components can be integrated. However, the components shown in FIG. 2 can also be realized by software using a computer.

  The computer comprises a CPU, a disk device such as a hard disk (may be a memory such as a ROM), a memory such as a RAM, a display unit such as a liquid crystal display, an information output unit 22, an intermediate data generation unit 23, and an expanded key generation The operations of the unit 20 and the data agitation unit 21 are described by a program, this program is stored in a disk device such as a hard disk, information (intermediate data, etc.) necessary for the operation is stored in a memory such as a RAM, and the CPU By operating the, the function of the encryption device of the present embodiment can be realized by a program. The program can be read into a computer by recording it on a computer-readable recording medium such as a DVD, CD-ROM, or USB memory and installing it on a hard disk.

  Each of the above-described embodiments is a preferred embodiment of the present invention. However, the scope of the present invention is not limited only to the above-described embodiment, and various modifications are made without departing from the gist of the present invention. Implementation is possible. Therefore, each embodiment mentioned above is only an illustration, and should not be interpreted limitedly. The scope of the present invention is indicated by the claims, and is not restricted by the description or the abstract. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  A part or all of the above embodiment can be described as in the following supplementary notes, but is not limited to the following configuration.

(Appendix 1)
An expanded key generating means for generating an expanded key from the encryption key;
A first counter value based on encrypted data is held, and when the data length of the encrypted data is greater than or equal to a predetermined data length, the first counter value is output and the first counter value is updated Holding the counter value as a second counter value, and holding a second counter value that is the same value as the first counter value when the data length of the encrypted data is less than a predetermined data length; Information output means for outputting a counter difference between the first counter value and the second counter value that is an updated counter value or the same as the first counter value;
Intermediate data generating means for determining a range of intermediate data generated from the extended key and the first counter value based on the counter difference, and outputting the generated intermediate data;
Data agitation means for encrypting and outputting the output intermediate data using the expanded key;
An encryption device comprising:

(Appendix 2)
The encryption apparatus according to attachment 1, wherein the information output unit includes a remaining data length holding unit that holds a data length or a remaining data length of the encrypted data, and a first counter that holds the first counter value. A second counter that holds the second counter value that is the updated counter value or the same as the first counter value, and data of encrypted data held in the remaining data length holding means Control means for instructing update of the first counter value when the length or the remaining data length is equal to or greater than a predetermined data length; and updating the first counter value according to an instruction from the control means to Counter updating means for holding the counter as the second counter value, the first counter value, the updated counter value or the first counter value And a difference calculating means for outputting the counter difference between the second counter value Flip become,
The remaining data length holding means holds the data length of the encrypted data, and outputs the block length when the data length is equal to or greater than the block length, subtracts the block length from the data length, and An encryption apparatus that retains the remaining data length in a length retaining unit.

(Appendix 3)
The encryption apparatus according to appendix 1 or 2, further comprising arithmetic means for performing an exclusive OR of the encrypted intermediate data with plaintext data.

(Appendix 4)
Generate an extended key from the encryption key,
A first counter value based on encrypted data is held, and when the data length of the encrypted data is greater than or equal to a predetermined data length, the first counter value is output and the first counter value is updated Holding the counter value as a second counter value, and holding a second counter value that is the same value as the first counter value when the data length of the encrypted data is less than a predetermined data length; Outputting a counter difference between the first counter value and the second counter value that is an updated counter value or the same as the first counter value;
Based on the counter difference, determine a range of intermediate data to be generated from the extended key and the first counter value, and output the generated intermediate data,
An encryption method for encrypting and outputting the output intermediate data using the extended key.

(Appendix 5)
The encryption method according to appendix 4, wherein the data length or the remaining data length of the encrypted data is held in a remaining data length holding means, the first counter value is held in a first counter, and an updated counter The second counter value that is a value or the same as the first counter value is held in the second counter, and the data length or the remaining data length of the encrypted data held in the remaining data length holding means is When the data length is equal to or longer than a predetermined data length, the first counter value is updated and held in the second counter as the second counter value,
The remaining data length holding means holds the data length of the encrypted data, and outputs the block length when the data length is equal to or greater than the block length, subtracts the block length from the data length, and An encryption method for holding the remaining data length in the long holding means.

(Appendix 6)
6. The encryption method according to appendix 4 or 5, further comprising arithmetic means for exclusive-ORing the encrypted intermediate data with plaintext data.

(Appendix 7)
To a computer as an encryption device,
A function to generate an extended key from an encryption key;
A first counter value based on encrypted data is held, and when the data length of the encrypted data is greater than or equal to a predetermined data length, the first counter value is output and the first counter value is updated Holding the counter value as a second counter value, and holding a second counter value that is the same value as the first counter value when the data length of the encrypted data is less than a predetermined data length; A function of outputting a counter difference between the first counter value and the second counter value that is an updated counter value or the same as the first counter value;
A function of determining a range of intermediate data to be generated from the extended key and the first counter value based on the counter difference, and outputting the generated intermediate data;
An encryption program for executing the function of encrypting and outputting the output intermediate data using the extended key.

(Appendix 8)
In the encryption program described in Appendix 7,
In the computer,
The data length or the remaining data length of the encrypted data is held in the remaining data length holding unit, the first counter value is held in the first counter, and is the updated counter value or the first counter value When the second counter value that is the same as the second counter value is held in the second counter, and the data length or the remaining data length of the encrypted data held in the remaining data length holding means is a predetermined data length or more, A function of updating the first counter value and holding it as the second counter value in the second counter;
The data length of the encrypted data is held in the remaining data length holding means, and when the data length is equal to or greater than the block length, the block length is output, the block length is subtracted from the data length, and the remaining data length An encryption program for causing a holding unit to execute a function of holding the remaining data length.

(Appendix 9)
The encryption program according to appendix 7 or 8, wherein the computer executes an arithmetic function for performing an exclusive OR operation on the encrypted intermediate data with plaintext data.

  The present invention can be applied to uses such as concealment of communication data such as a voice communication terminal and a data communication device, and encryption of data stored on a storage.

DESCRIPTION OF SYMBOLS 2 Encryption apparatus 3 F function 4 Exclusive OR 20 Extended key production | generation part 21 Data stirring part 22 Information output part 23 Intermediate data generation part 500-522 Intermediate data 50-69 F function

Claims (9)

An expanded key generating means for generating an expanded key from the encryption key;
A first counter value based on encrypted data is held, and when the data length of the encrypted data is greater than or equal to a predetermined data length, the first counter value is output and the first counter value is updated Holding the counter value as a second counter value, and holding a second counter value that is the same value as the first counter value when the data length of the encrypted data is less than a predetermined data length; Information output means for outputting a counter difference between the first counter value and the second counter value that is an updated counter value or the same as the first counter value;
Intermediate data generating means for determining a range of intermediate data generated from the extended key and the first counter value based on the counter difference, and outputting the generated intermediate data;
Data agitation means for encrypting and outputting the output intermediate data using the expanded key;
An encryption device comprising: 2. The encryption apparatus according to claim 1, wherein the information output unit includes a remaining data length holding unit that holds a data length or a remaining data length of the encrypted data, and a first counter value that holds the first counter value. A counter, a second counter that holds the second counter value that is the updated counter value or is the same as the first counter value, and the encrypted data held in the remaining data length holding means Control means for instructing update of the first counter value when the data length or the remaining data length is greater than or equal to a predetermined data length, and the second counter value is updated by instructing the control means to update the first counter value. Counter updating means for holding the second counter value as the second counter value, the first counter value and the updated counter value or the first counter value And a difference calculating means for outputting the counter difference between the second counter value is the same,
The remaining data length holding means holds the data length of the encrypted data, and outputs the block length when the data length is equal to or greater than the block length, subtracts the block length from the data length, and An encryption apparatus that retains the remaining data length in a length retaining unit.   3. The encryption apparatus according to claim 1 or 2, further comprising arithmetic means for exclusive ORing the encrypted intermediate data with plain text data. Generate an extended key from the encryption key,
A first counter value based on encrypted data is held, and when the data length of the encrypted data is greater than or equal to a predetermined data length, the first counter value is output and the first counter value is updated Holding the counter value as a second counter value, and holding a second counter value that is the same value as the first counter value when the data length of the encrypted data is less than a predetermined data length; Outputting a counter difference between the first counter value and the second counter value that is an updated counter value or the same as the first counter value;
Based on the counter difference, determine a range of intermediate data to be generated from the extended key and the first counter value, and output the generated intermediate data,
An encryption method for encrypting and outputting the output intermediate data using the extended key. 5. The encryption method according to claim 4, wherein a data length or remaining data length of the encrypted data is held in a remaining data length holding unit, and the first counter value is held in a first counter and updated. The second counter value that is the counter value or the same as the first counter value is held in the second counter, and the data length or the remaining data length of the encrypted data held in the remaining data length holding means Is equal to or longer than a predetermined data length, the first counter value is updated and held in the second counter as the second counter value,
The remaining data length holding means holds the data length of the encrypted data, and outputs the block length when the data length is equal to or greater than the block length, subtracts the block length from the data length, and An encryption method for holding the remaining data length in the long holding means.   6. The encryption method according to claim 4 or 5, further comprising arithmetic means for exclusive ORing the encrypted intermediate data with plain text data. To a computer as an encryption device,
A function to generate an extended key from an encryption key;
A first counter value based on encrypted data is held, and when the data length of the encrypted data is greater than or equal to a predetermined data length, the first counter value is output and the first counter value is updated Holding the counter value as a second counter value, and holding a second counter value that is the same value as the first counter value when the data length of the encrypted data is less than a predetermined data length; A function of outputting a counter difference between the first counter value and the second counter value that is an updated counter value or the same as the first counter value;
A function of determining a range of intermediate data to be generated from the extended key and the first counter value based on the counter difference, and outputting the generated intermediate data;
An encryption program for executing the function of encrypting and outputting the output intermediate data using the extended key. In the encryption program according to claim 7,
In the computer,
The data length or the remaining data length of the encrypted data is held in the remaining data length holding unit, the first counter value is held in the first counter, and is the updated counter value or the first counter value When the second counter value that is the same as the second counter value is held in the second counter, and the data length or the remaining data length of the encrypted data held in the remaining data length holding means is a predetermined data length or more, A function of updating the first counter value and holding it as the second counter value in the second counter;
The data length of the encrypted data is held in the remaining data length holding means, and when the data length is equal to or greater than the block length, the block length is output, the block length is subtracted from the data length, and the remaining data length An encryption program for causing a holding unit to execute a function of holding the remaining data length.   9. The encryption program according to claim 7 or 8, wherein the computer is caused to execute a calculation function for exclusive ORing the encrypted intermediate data with plain text data.

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