JPH10149101A - Cipher converting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the cipher converting device which executes ciphering algorithm performing 4-byte based processing oriented to a 32-bit microcomputer. SOLUTION: The cipher converting device is equipped with a providing means which provides data M of (n)-bit length to be ciphered and a ciphering device which ciphers the data M provided by the providing means into data C of (n)-bit length by using key data K1 and K2 of (n)-bit length. The ciphering device has a means which generates the data C by performing a process including operation prescribed by a function π for the data M by using the key data K1 and K2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a cryptographic conversion device.

[0002]

2. Description of the Related Art Conventional typical encryption algorithms include DES (Data Encryption Standard) and FEAL.
(Fast Encryption Standard) is known and DES
For example, (1) Koyama et al., "Modern Cryptography",
IEICE, pp. 41-49, September 1986, and regarding FEAL, (2) Shimizu et al., "High-speed Data Encryption Algorithm FEAL", IEICE Transactions D, Vol. J70-D. No. 7, pp. 141
3-1423, July 1987, respectively.

First, a non-linear calculation part in the DES process, that is, a process called an S box will be described (see (1) p. 45, FIGS. 3-2 and p 46, FIG.
3). The 32-bit R is first replaced by the extended transposition table shown in Table 1, and some bits are duplicated and expanded to 48 bits.

[0004]

[Table 1]

[0005] The thus obtained 48-bit R
Forms eight sets of 6-bit blocks, each of which is obtained by adding the following two bits for every four bits from the beginning.

R31 r1 r2 r3 r4 r5, r4 r5 r6 r7 r8 r9, r8 r9 r10 r11 r12 r13, r12 r13..., R28 r29, r28 r29 r30 r31 r32 r31 Similarly, an exclusive OR operation with the 48-bit key K is performed, and the result is divided into eight sets of 6 bits each and input to eight S boxes from S1 to S8.
S1 to S8 are called selection functions. These S boxes are
Input 6 bits and output 4 bits.

As an example, Table 2 shows a substitution table for one S box S1.

Table 2 Enlarged transposition table E 32 1 2 3 4 5 4 5 6 7 8 9 8 9 10 11 12 13 12 13 14 15 16 17 16 17 18 19 20 21 20 21 22 23 24 25 24 25 26 27 28 29 28 29 30 31 32 1 One S box has four types (line numbers 0, 1, 2,
3) is prepared, and the substitution table is selected by using the first and last bits of the input 6 bits to determine which of the four types of substitution table is used. Then, the central 4 bits of the 6 bits input according to the selected substitution table are substituted. As a specific example, the binary input pattern is 01 for S1.
If it is 1011, 01 represented by the first 0 and the last 1, that is, row 1 (binary 01 is decimal 1
) Is selected. Next, a column 1 represented by a central 4-bit pattern 1101 (decimal 13)
3 is output, and as a result, the value 5 specified in the row 1 and the column 13, that is, 0101 is output to form a 4-bit substitution pattern. In the DES, a single-stage process is configured using such a process f (R, K), and this is repeated 16 stages.

As can be seen from the above processing example, DES is based on 1-bit unit processing.

Next, a non-linear calculation part in the FEAL process, that is, a part including the function S will be described (see p. 1416 of (2) above, FIGS. 4 and 5).
The non-linear part of FEAL is easier to describe mathematically than the non-linear part of DES. The 32-bit data α is divided into 8-bit data α ⁰ , α ¹ , α ² , α ³ and then divided into 8 bits.
As a bit unit, the key data and the exclusive OR are calculated. After that, processing by a predetermined function S is performed.

Function S: S (x1 + x2 + δ) = Rot2 (w) where w = (x1 + x2 + δ) mod 256 δ = 0 or 1 (constant) Using this process f (α, β), a one-stage process is configured. Repeated eight steps. As seen in the above process,
FEAL is based on 8-bit processing.

[0012]

With the spread and widespread use of computer networks due to advances in information processing and communication technology, data and computers on transmission lines are required to secure information security against unauthorized use or capture of data. It is considered that encrypting the data stored in the server is an effective countermeasure.

DES, established in 1982 by the United States Department of Commerce as a standard for encryption algorithms, is one means of encrypting data.

However, since DES has a large number of processing in bit units, it takes a long time to implement it with microcomputer software based on byte processing, and a practical speed cannot be obtained. .

In order to solve this problem, the FEAL is based on processing in units of 1 byte (8 bits). Therefore, when the FEAL is realized by an 8-bit microcomputer, it is possible to achieve several times higher speed than DES. did it. It is considered that FEAL has made it possible to obtain a practical speed to some extent using software of an 8-bit microcomputer.

However, due to recent advances in microelectronics technology, 16-bit microcomputers have been replaced by 8-bit microcomputers, and 16-bit microcomputers.
32-bit microcomputers have been used rather than bit microcomputers. It is anticipated that the use of 32-bit microcomputers will increase significantly in the near future. In the era of 32-bit microcomputers, higher-speed encryption processing is expected to be required. However, since a 32-bit microcomputer performs processing based on 4-byte data, an F designed for an 8-bit microcomputer based on 1-byte data is used.
Attempting to implement the EAL with a 32-bit microcomputer was inefficient.

Therefore, there has been a demand for an encryption algorithm for a 32-bit microcomputer that performs a 4-byte key processing.

An object of the present invention is to provide a cryptographic conversion device for executing a cryptographic algorithm for performing a 4-byte key processing for a 32-bit microcomputer. In particular, the encryption conversion device of the present invention includes a unit for providing data to be encrypted and an encryption device for performing encryption conversion, and the encryption device alternately performs a substitution process and a cyclic shift process, The first and second cyclic shifts are different in the number of bits.

[0019]

To solve the above problems, the following means are used.

That is, the cipher conversion device of the present invention comprises: a providing means for providing n-bit data M to be encrypted;
An encryption device for encrypting the data M provided from the providing unit into data C having an n-bit length using key data K1 and K2 each having an n-bit length, wherein the encryption device comprises: Substitution processing is performed using key data K1 with π (A) as A, cyclic shift processing is performed using the first number of bits, substitution processing is performed using key data K2, and a second bit number different from the first is used. And a function for outputting the result of performing the cyclic shift process in the first storage means for holding the two key data K1 and K2, and the data M provided by the first providing means, By executing a process including an operation defined by a function π using the key data K1 and K2 held by
And a second holding unit for holding the generated ciphertext C.

As a result, since the 32-bit data is replaced or transposed by one basic instruction using the 32-bit microcomputer, the cryptographic conversion can be performed at high speed.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

 (1) First Embodiment FIG. 1 shows an embodiment of the present invention.

In FIG. 1, a 64-bit plaintext 101 and a 64-bit × 4 = 256-bit key data 100 are 32 bits.
Input to the 32-bit microcomputer 102, and thereafter, are cryptographically converted by the 32-bit microcomputer 102 in the order of the instructions in the program 103.
The 4-bit ciphertext 104 is output.

FIG. 2 shows a flow of a cryptographic conversion process executed by the 32-bit microcomputer 102 and the program 103 in FIG.

201: The input data M is divided into upper 32 bits M1 and lower 32 bits M2.

202: An exclusive OR operation corresponding to the bits of M1 and M2 is performed.

WORK2 ← M1 (+) M2 Hereinafter, (+) indicates the same processing. In the figure, the exclusive OR is indicated by a symbol obtained by superimposing ○ and +.

203: Modulo addition of WORK2 and key data K1 is performed.

X ← WORK2 + K1 Here, x + K1 indicates a modulo addition modulo 2 ^{32 in} which the remainder of the sum of x and K1 is divided by 2 ³² .

Hereinafter, + indicates the same processing.

204: After x is cyclically shifted left by 2 bits, modulo addition of the data and x and 1 is performed.

X ← Rot2 (x) + x + 1 Hereinafter, Rot2 indicates the same processing.

105: After x is cyclically shifted left by 4 bits, exclusive OR of the data and x is obtained.

X ← Rot4 (x) (+) x Hereinafter, Rot4 indicates the same processing.

206: WORK1 ← x (+) M1 207: x ← x + K2 208: x ← Rot2 (x) + x + 1 y ← x209: x ← Rot3 (x) (+) x Here, Rot3 (x) is x Is cyclically shifted left by 8 bits.

210: x ← x + K3 211: x ← Rot2 (x) + x + 1 212: x ← Rot16 (x) + (x∧y) where Rot16 (x) shifts x to the left by 16 bits. Show. In addition, x∧y indicates that a logical AND of x and y corresponding to bits is taken.

213: WORK2 ← x (+) WORK2 214: x ← WORK2 + K4 215: x ← Rot2 (x) + x 216: WORK1 ← WORK1 (+) x 217: WORK2 ← WORK2 (+) WORK1 218: Output data of WORK1 Upper 32 bits of W
ORK2 is output as the lower 32 bits of the output data.

As described above, when the functions π1 to π4 are defined as shown in FIG. 2, this embodiment can be represented by a composite function as follows: C = π1, π4, π3, π2, π1 (M).

The functions πi · πi (i = 1 to 4) all have the property of repeating the same function conversion twice and returning as πi · πi (x) = x.

Therefore, if M = π1, π2, π3, π4, π1 (C) is used as the decryption function, the ciphertext C can be returned to the original plaintext M.

(2) Modification 1 of the embodiment A process obtained by repeating the process corresponding to the conversion functions π1 to π4 twice in the above embodiment may be used as a cryptographic conversion.・ Π3 ・ π2 ・ π1 ・ π4 ・ π3 ・ π2
・ It may be π1 (M).

At this time, the equation of the decoding conversion is M = π1, π2, π3, π4, π1, π2, π3, π4.
Π1 (C)

Similarly, in general, the present embodiment may be repeated n times and used as the cryptographic conversion.

(3) Second Modification of Embodiment FIG. 4 shows another embodiment of the present invention.

401: Input data M is divided into upper 16 bits M1 and lower 16 bits M2.

402: Exclusive OR corresponding to the bits of M1 and M2 is calculated.

WORK2 ← M1 + M2 Hereinafter, + indicates the same processing.

403: Modulo subtraction of x and key data K1 is performed.

X ← x−K1 Here, x−K1 indicates a modulo subtraction modulo 2 ^16, that is, the remainder obtained by dividing the difference between x and K1 by 2 ¹⁶ .

Hereinafter, "-" indicates the same processing.

404: After cyclically shifting x by 2 bits to the left, modulo subtraction of the data and 1 is performed.

X ← Rot (x) −x−1 Hereinafter, Rot2 indicates the same processing.

405: After x is cyclically shifted left by 4 bits, exclusive OR of the data and x is obtained.

X ← Rot4 (x) (+) x Hereinafter, Rot4 indicates the same processing.

406: WORK1 ← x (+) M1 407: x ← x−K2 y ← x 408: x ← Rot2 (x) −x−1 409: Rot8 (x) − (x∧y) where Rot8 (X) indicates that x is cyclically shifted left by 8 bits. In addition, x∧y indicates that a logical AND of x and y corresponding to bits is taken.

410: WORK2 ← x (+) WORK2 411: x ← WORK2-K3 412: x ← Rot2 (x) -x-1 413: WORK1 ← WORK1 (+) x 414: WORK2 ← WORK2 (+) WORK1 415 : WORK1 as upper 16 bits of output data, W
ORK2 is output as the lower 16 bits of the output data.

(4) Third Modification of Embodiment FIG. 5 shows another embodiment of the present invention.

501: Input data M is divided into upper 8 bits M1 and lower 8 bits M2.

502: Exclusive OR of the bits corresponding to M1 and M2 is performed.

WORK2 ← M1 (+) M2 Hereinafter, + indicates the same processing.

503: Modulo addition of x and key data K1 is performed.

X ← WORK2 + K1 y ← x Here, x + K1 indicates a modulo addition modulo 2 ^{8 in} which the difference between x and K1 is divided by 2 ⁸ .

Hereinafter, + indicates the same processing.

504: After cyclically shifting x by 2 bits to the left, modulo addition of the data and x and 1 is performed.

X ← Rot2 (x) + x + 1 Hereinafter, Rot2 indicates the same processing.

505: x ← Rot4 (x) + (x∧y) Here, Rot4 (x) indicates that x is cyclically shifted to the left by 4 bits. In addition, x∧y indicates that a logical AND of x and y corresponding to bits is taken.

506: WORK1 ← WORK1 (+) x 507: x ← WORK1 + K2 508: x ← Rot4 (x) + x + 1 509: WORK2 ← WORK2 (+) x 510: WORK1 ← WORK1 (+) WORK2 511: Output data of WORK1 Upper 8 bits of WO
RK2 is output as the lower 8 bits of the output data.

(5) Fourth Modification of Embodiment FIG. 6 shows another embodiment of the present invention.

(1) Using a message 62 for performing authentication as key data, an arbitrary initial value 61 is encrypted using an algorithm 63 according to the present invention.

(2) The encryption result 64 is encrypted again with the subsequent data of the message used in (1), and this operation is repeated until the end of the message.

(3) The final encryption result is output as the message authentication code 65.

(6) Modification 5 of Embodiment FIG. 7 shows another embodiment of the present invention. This IC card generates an authentication code of the message.

(1) An initial value 76 necessary for message authentication is transmitted to the microcomputer 72 in the IC card 71 through the I / O 74.

(2) A message 77 for performing authentication is sent to (1)
The microcomputer 72 generates the authentication code 78 using the encryption software 75 stored in the memory 73 in the same manner as described above.

[0075]

In the present embodiment, substitution and transposition as shown in FIG. 3 are repeated.

That is, in the embodiment shown in FIG.
04), (207, 208), (210, 211),
The processing of (214, 215) has the form of x ← x + Kix ← Rot2 (x) + (x) +1, which is obtained by dividing 32-bit data into blocks each having 4 bits. Substitution processing for each block is performed by the above two data conversions.
It can be seen that they are going all at once for the block.

Here, 4-bit block data A = (a1, a2, a3, a4), where ai = 1 or 0 (i = 1 to 4), B = (b1, b2, b3, b4) However, the fact that the substitution conversion is made to bi = 1 or 0 (i = 1 to 4) means that the pool algebra operation f
1, f2, f3, and f4 exist; b1 = f1 (a1, a2, a3, a4) b2 = f2 (a1, a2, a3, a4) b3 = f3 (a1, a2, a3, a4) b4 = f4 (a1, a2, a3, a4).

Further, 205, 209 and 212 in FIG. 2 are (1) x ← Rot4 (x) (+) x (2) x ← Rot8 (x) (+) x (3) x ← Rot16 (x ) + (X∧y), which are (1) transposed to perform a 4-bit left circular shift and then further substituted, (2) 8-bit left circular The figure shows a process of performing a transposition after performing a transposition of performing a shift, and a process of performing (3) a 16-bit left circular shift.

As is apparent from FIG. 3, any bit change in the first 32 bits of data is the last 32 bits.
It can be seen that all bits of data are affected.

As a result, it is understood that the present embodiment has an effect of efficiently performing encryption conversion having a high degree of randomness.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a cryptographic conversion device for implementing the present invention.

FIG. 2 is a flowchart showing details of encryption conversion in FIG. 1;

FIG. 3 is an explanatory diagram showing that the embodiment of the present invention efficiently repeats substitution conversion and transposition conversion.

FIG. 4 is a flowchart showing details of cryptographic conversion when a 16-bit microcomputer is used.

FIG. 5 is a flowchart showing details of encryption conversion when an 8-bit microcomputer is used.

FIG. 6 is a flowchart illustrating a method for generating a message authentication code using a cryptographic algorithm according to the present invention.

FIG. 7 is a configuration diagram of an IC card that generates a message authentication code using an encryption algorithm according to the present invention.

[Explanation of symbols]

100: key data, 101: plaintext, 102: 32-bit microcomputer, 103: program, 104:
Ciphertext.

Claims (4)

[Claims] 1. A providing means for providing n-bit length data M to be encrypted, and said data M provided by said providing means is provided with n-bit length data using key data K1 and K2 each having n-bit length. An encryption device for performing encryption conversion to convert the data into the data C, wherein the encryption device performs a substitution process using π (A) for A and the key data K1,
A cyclic shift process is performed with the first bit number, and key data K
2 as a function for performing a substitution process using the second key data and performing a cyclic shift process with a second bit number different from the first bit number, and a first holding unit for holding the two key data K1 and K2; For the data M provided by the first providing means,
The key data K1 and K1 held by the first holding unit
2. A cipher comprising: means for generating the data C by executing a process including an operation defined by a function π by using the function C.2; and second holding means for holding the generated ciphertext C. Conversion device. 2. The apparatus according to claim 1, further comprising means for generating the data C by executing a process including an operation defined by a function π a plurality of times on the data M. Cryptographic converter. 3. A providing means for providing data C having an n-bit length to be decrypted, and said data M provided from said providing means being provided with an n-bit length using key data K1 and K2 each having an n-bit length. And a decryption device for decrypting and converting the data M into the data M. The decryption device performs a substitution process using π (A) as A and key data K1,
A cyclic shift process is performed with the first bit number, and key data K
2 as a function for performing a substitution process using the second key data and performing a cyclic shift process with a second bit number different from the first bit number, and a first holding unit for holding the two key data K1 and K2; For the data M provided by the first providing means,
The key data K1 and K1 held by the first holding unit
2, a means for generating the data M by executing a process including an operation defined by a function π, and a second holding means for holding the generated data M apparatus. 4. The apparatus according to claim 3, further comprising means for generating the data M by executing a process including an operation defined by a function π a plurality of times on the data C. Cryptographic converter.