JP2001013870A - Method of common key enciphering or deciphering, and recording medium with common key ciphering or deciphering program recorded thereon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a common key ciphering method virtually disabling a known plaintext attack and a selected plaintext attack. SOLUTION: The disclosed common key enciphering method enciphers a plaintext by preparing a table of random digits and a reading mechanism 1, an indirect index array 2, and a four-dimensional matrix 4 with constant coefficients beforehand, deciding display start positions of each step of the table of random digits from a secret key 6, calculating (p+q) pieces of original maps by the table of random digits and the reading mechanism 1 every time m-bytes of character string is taken out of a plaintext, generating a 1st indirect index array presenting a composited map of the p-pieces of original lamp numbers and a 2nd indirect index array presenting a composited map of the q-pieces of original map numbers, converting the character string taken out of the plaintext data by the 1st indirect index array, converting the character string of this conversion result by integrating it with m-dimensional matrix with constant coefficients, and storing in the ciphertext a character string obtained by converting the character string of the conversion result by the 2nd indirect index array.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a common key encryption or decryption method using a common secret key for encryption and decryption, and a storage medium storing a common key encryption or decryption program. .

[0002]

2. Description of the Related Art Conventionally, this type of encryption system is designed to secure the security of encrypted data against an attacker who attempts to decrypt a ciphertext without knowing the contents of a secret key. Used for purposes. For example, DES (Data Encryption Standard), which is an encryption standard currently standardized in the United States, is used as a block type encryption system.
Cryptography is widely used. However, in DES, there is a risk of being decrypted by a means called a differential analysis method by a selective plaintext attack and by a means called a linear decryption method by a known plaintext attack. This is because the DES performs only a transformation having a linear property, that is, an exclusive OR, other than the transposition.

[0003] In addition, DES is slow as a program on a computer, but when an attacker uses dedicated hardware, only the attacker has an advantage and the user has a disadvantage. Disadvantage. This is because DES makes heavy use of transposition and exclusive OR for each bit, which are slow in execution speed on a computer. On the other hand, Japanese Patent Application Laid-Open No. Hei 10-123949 (Japanese Patent Application No. 9-217299) discloses a technique in which DES encryption is improved to enhance security against differential analysis. However, this conventional technique still has a problem that the processing is slow as a program on a computer. This is because, even in this conventional technique, a process that is slow in execution speed on a computer, that is, bit transposition, is often used.

On the other hand, as another encryption method, there is a stream type encryption method. For example, Japanese Patent Application Laid-Open No. 9-288565
In Japanese Unexamined Patent Application Publication No. 8-99985, a technique for generating and using a real-valued random number sequence along a chaotic orbit is disclosed. However, this conventional technique has a problem that it is difficult to guarantee the same operation on a plurality of computers having different architectures. This is because the real-valued random number sequence is calculated by repeating the real number operation, so due to a slight difference in the computer architecture,
This is because the generated random number sequence may be different. Further, in the above-described conventional technology, there is a problem that it is not possible to guarantee the avoidance of such a risk with respect to the risk that the random number sequence falls into a short period. This is because, in the real number operation of the self-excited system that generates chaos, it is difficult to find a periodic point, but it does not guarantee that it is not in a short period.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a common key encryption system using a common key for encryption processing and decryption processing. It is an object of the present invention to provide a common key encryption or decryption method and a storage medium recording a common key encryption or decryption program, which makes a known plaintext attack and a selective plaintext attack virtually impossible.

[0006]

Means for Solving the Problems To solve the above problems, the invention according to claim 1 relates to a common key encryption method,
Based on a long-period random number table and the display value of the random number table, (p +
q) (p and q are arbitrary natural numbers; hereinafter, abbreviated) read-out mechanisms for calculating the original mapping numbers, an indirect index array representing each original mapping, and an m-th order matrix of constant coefficients are prepared in advance. When the secret key is designated, the display start position of the random number table is determined from the secret key, and each time an m-byte character string is extracted from the plaintext data, the (p + q) The number of the original mapping is calculated, a first indirect index array representing a composite mapping of the original mappings indicated by the p original mapping numbers in the (p + q) original mapping numbers, and the (p + q) And a second indirect index array representing a composite mapping of the original mappings indicated by the q original mapping numbers in the original mapping numbers, and converting the character string extracted from the plaintext data into the first indirect index array And then convert the resulting string to the constant Converted by multiplication of the number of m-order matrix,
Further, a process of storing a character string obtained by converting the character string obtained as a result of the conversion using the second indirect index array into the ciphertext data as a m-byte character string in the ciphertext data includes: Each time a character string of m bytes is read, plain text is encrypted by repeating the display position of each row of the random number table while shifting it one by one.

According to a second aspect of the present invention, there is provided a common key decryption method, comprising: a long-period random number table; and a reading mechanism for calculating (p + q) original mapping numbers based on the display value of the random number table. An indirect index array representing an inverse mapping of each original mapping and an inverse matrix of an m-th order matrix of constant coefficients are prepared in advance, and when a secret key is designated, a display start position of the random number table is determined from the secret key. After that, every time an m-byte character string is extracted from the ciphertext data, the numbers of the (p + q) original mappings are calculated by the random number table and the reading mechanism, and the (p + q) original mapping numbers are calculated. A first indirect index array representing a composite mapping of the inverse mapping of the order of the original mappings indicated by the p original mapping numbers in the order of the encryption, and q of the (p + q) original mapping numbers Reverse mapping of the array in the reverse order of the encryption of the original mapping indicated by the original mapping number And a second indirect index array representing the composite map of the above is converted, and the character string extracted from the ciphertext data is converted by the second indirect index array. The conversion is performed by multiplying the coefficient by the inverse matrix of the m-th order matrix, and the character string obtained by converting the conversion result using the first indirect index array is represented by m in the plaintext data.
The process of storing the character string of bytes in the plaintext data is such that the display position of each row of the random number table is shifted one by one in the direction opposite to that at the time of encryption every time the character string of m bytes is read from the ciphertext data. It is characterized in that the encryption is decrypted by repeating the above.

According to a third aspect of the present invention, there is provided a symmetric key encryption method, comprising: a long-period random number table; and a reading mechanism for calculating (p + q) original mapping numbers based on display values of the random number table. , An indirect index array representing each original mapping and an m-th order matrix of constant coefficients are prepared in advance, and when a secret key is designated,
After determining the display start position of the random number table from the secret key, every time a vector of a predetermined number of m-byte elements is extracted from the plaintext data, the random number table and the reading mechanism read out the elements several times and read the same. The numbers of the (p + q) original mappings are calculated, and the p original mapping numbers in the (p + q) original mapping numbers used for each element are set to the first.
And the q original mapping numbers in the (p + q) original mapping numbers used for each element are stored in the second working vector, and each element of the vector extracted from the plaintext data is stored. Is converted using an original mapping indicated by the p-th original mapping number included in each element of the first work vector, and then each element of the vector of the conversion result is converted into an m-th order of the constant coefficient. It converts by multiplication with a matrix, and further converts each element of the vector of the conversion result using the original mapping indicated by the q-th original mapping number included in each element of the second work vector. The process of storing the obtained vector in the ciphertext data as a vector of a predetermined number of m-byte elements in the ciphertext data is performed by reading the vector of the predetermined number of m-byte elements from the plaintext data. Of each row of the random number table By repeated while shifting the shown position one by one, it is characterized by performing the encryption of the plaintext.

According to a fourth aspect of the present invention, there is provided a symmetric key decryption method, comprising: a long-period random number table; and a reading mechanism for calculating (p + q) original mapping numbers based on display values of the random number table. An indirect index array representing an inverse mapping of each original mapping and an inverse matrix of an m-th order matrix of constant coefficients are prepared in advance, and when a secret key is designated, a display start position of the random number table is determined from the secret key. After that, every time a vector of a predetermined number of m-byte elements is extracted from the ciphertext data, the random number table and the reading mechanism read out the elements several times and calculate the numbers of the (p + q) original maps. Then, the p original mapping numbers in the (p + q) original mapping numbers used for each element are stored in the first work vector in the reverse order of the encryption, and the (p + q) used for each element is stored. Q) of the original mapping numbers The original mapping numbers are stored in the second work vector in the reverse order of the encryption, and each element of the vector extracted from the ciphertext data is replaced with the q original work numbers included in each element of the second work vector. The conversion is performed using the inverse mapping of the original mapping indicated by the mapping number, and then each element of the vector of the conversion result is converted by multiplication with the inverse matrix of the m-th order matrix of the constant coefficient. A vector obtained by transforming each element using the inverse mapping of the original mappings indicated by the p original mapping numbers included in each element of the first working vector is defined by m bytes in plaintext data. The process of storing in the plaintext data as a vector of a number of elements is performed by reading the display position of each row of the random number table every time a vector of a predetermined number of m-byte elements is read from the ciphertext data. Repeat while shifting one by one in the direction By Succoth, it is characterized by performing decoding of Kurabun.

According to a fifth aspect of the present invention, there is provided a storage medium storing a common key encryption program, and a computer readable storage medium storing a program for executing the common key encryption method according to the first aspect. A long-period random number table, a read-out mechanism for calculating (p + q) original mapping numbers based on display values of the random number table, an indirect index array representing each original mapping, and an m-th order matrix of constant coefficients Are prepared in advance, and when a secret key is designated, a display start position of the random number table is determined from the secret key, and each time an m-byte character string is extracted from the plaintext data, Calculating a number of the (p + q) original mappings, a first indirect index array representing a composite mapping of the original mappings indicated by the p original mapping numbers in the (p + q) original mapping numbers, (P + ) Original mapping numbers, and a second indirect index array representing a composite mapping of the original mappings indicated by the q original mapping numbers, and converting the character string extracted from the plaintext data into the first The conversion is performed using an indirect index array, the converted character string is converted by multiplying the constant coefficient with the m-th order matrix, and the converted character string is further converted using the second indirect index array. The process of storing the character string in the ciphertext data as the m-byte character string in the ciphertext data is performed by reading the display position of each row of the random number table every time the m-byte character string is read from the plaintext data. It is characterized in that a program for encrypting a plaintext is recorded by repeating it while shifting it one by one.

According to a sixth aspect of the present invention, there is provided a storage medium storing a common key decryption program, and a computer readable storage medium storing a program for executing the common key decryption method according to the second aspect. A long-period random number table, a read-out mechanism for calculating (p + q) original mapping numbers based on the display values of the random number table, an indirect index array representing an inverse mapping of each original mapping, and a constant coefficient When an inverse matrix of an m-th order matrix is prepared in advance, and a secret key is designated, a display start position of the random number table is determined from the secret key. The numbers of the (p + q) original mappings are calculated by a random number table and a readout mechanism, and the order of the original mappings indicated by the p original mapping numbers in the (p + q) original mapping numbers is the reverse of that at the time of encryption. Of the inverse map of the array It represents a composite mapping of a first indirect index array representing a mapping and an inverse mapping of an array in an order reverse to that at the time of encryption of the original mapping indicated by the q original mapping numbers in the (p + q) original mapping numbers. A second indirect index array is created, and the character string extracted from the ciphertext data is converted by the second indirect index array. Is converted by multiplication with the inverse matrix of the above, and a character string obtained by converting the character string resulting from the conversion with the first indirect index array is stored in the plaintext data as a m-byte character string in the plaintext data. Each time the m-byte character string is read from the ciphertext data, the process is repeated while shifting the display position of each row of the random number table one by one in a direction opposite to the encryption, thereby decoding the ciphertext. Is recorded.

According to a seventh aspect of the present invention, there is provided a storage medium storing a common key encryption program, and a computer readable storage medium storing a program for executing the common key encryption method according to the third aspect. A long-period random number table, a read-out mechanism for calculating (p + q) original mapping numbers based on display values of the random number table, an indirect index array representing each original mapping, and an m-th order matrix of constant coefficients Are prepared in advance, and when a secret key is designated, the display start position of the random number table is determined from the secret key. Each time a vector of a predetermined number of m bytes is extracted from the plaintext data, the random number table is extracted. And the reading mechanism perform reading of the element several times and calculation of the numbers of the (p + q) original mappings, and the p original mapping numbers in the (p + q) original mapping numbers used for each element Is stored in a first work vector, and q original mapping numbers in the (p + q) original mapping numbers used for each element are stored in a second work vector, and a vector extracted from the plaintext data is stored. Are converted using the original mappings indicated by the p original mapping numbers included in each element of the first work vector, and then each element of the vector of the conversion result is converted to the constant coefficient The conversion is performed by multiplication with the m-th order matrix, and each element of the vector of the conversion result is further converted using the original mapping indicated by the q original mapping numbers included in each element of the second work vector. The process of storing the obtained vector in the ciphertext data as a vector for a predetermined number of m-byte elements in the ciphertext data is performed every time a vector for a predetermined number of m-byte elements is read from the plaintext data. Each of the above random number tables By repeated while shifting the display position of the one by one, it is characterized by recording a program for encrypting plaintext.

The invention according to claim 8 relates to a storage medium storing a common key decryption program, and a computer readable recording medium storing a program for executing the common key decryption method according to claim 4. A long-period random number table, a read-out mechanism for calculating (p + q) original mapping numbers based on the display values of the random number table, an indirect index array representing an inverse mapping of each original mapping, and a constant coefficient When an inverse matrix of an m-th order matrix is prepared in advance and a secret key is specified, a display start position of the random number table is determined from the secret key, and then a vector of a predetermined number of m-byte elements is obtained from the ciphertext data. Each time it is taken out, the above-mentioned random number table and read-out mechanism are used to read out the element several times and calculate the numbers of the (p + q) original mappings, and use the (p + q) for each element.
The p original mapping numbers in the original mapping numbers are stored in the first working vector in the reverse order of the encryption, and the q original mapping numbers in the (p + q) original mapping numbers used for each element are stored. The mapping numbers are stored in the second work vector in the reverse order of the encryption, and each element of the vector extracted from the ciphertext data is replaced with the q original maps included in each element of the second work vector. The conversion is performed using the inverse mapping of the original mapping indicated by the number, and then each element of the vector of the conversion result is converted by multiplication with the inverse matrix of the m-order matrix of the constant coefficient. A vector obtained by transforming an element using the inverse mapping of the original mappings indicated by the p original mapping numbers included in each element of the first work vector is converted into a predetermined number of m bytes in the plaintext data. To store in plaintext data as a vector of Is repeated while shifting the display position of each row of the random number table one by one in a direction opposite to that at the time of encryption every time a vector of a predetermined number of m-byte elements is read from the encrypted data. The program is characterized by recording a program for decrypting.

[0014]

According to the structure of the present invention, when a plaintext is encrypted, a display start position on the random number table and the reading mechanism is determined when a secret key is given. Next, from the plaintext data,
Each time the m-byte character string in the plaintext data is read, the value is read from the random number table and the reading mechanism and used (p +
q) Determine the numbers of the original maps. The m-byte character string in the plaintext data is first converted by an indirect index array, which is a composite mapping of the p original mapping numbers of the original mapping, and then converted by multiplication with an m-th order matrix. The conversion is performed by an indirect index array, which is a composite mapping of q original mapping numbers of the mapping, to generate an m-byte character string in the ciphertext data. Conversely, when decrypting a ciphertext, when a secret key is given, the display start position on the random number table and the reading mechanism is determined. Next, every time an m-byte character string in the ciphertext data is read from the ciphertext data, a value is read from the random number table and the reading mechanism, and the numbers of (p + q) original maps to be used are determined. The m-byte character string in the ciphertext data is first converted by an indirect index array, which is a composite map of the inverse mapping of the q original mapping numbers of the original mapping, and then multiplied by the inverse matrix of the m-th order matrix And finally converted by an indirect index array, which is a composite mapping of the inverse mapping of the p original mapping numbers of the original mapping, to generate an m-byte character string in the plaintext data.

In another configuration of the present invention, when encrypting plaintext, a display start position on a random number table is determined when a secret key is given. Next, from the plaintext data,
Each time a vector of m bytes x a predetermined number of elements in the plaintext data is read, a value is read from the random number table and the reading mechanism,
The number of (p + q) original maps to be used is determined. A vector of m bytes × predetermined number of elements in the plaintext data is first converted (list vector load) using an original mapping of a work vector storing p original mapping numbers used for each element, and then the m-th order vector is loaded. It is converted by multiplication with a matrix, and finally converted (list vector loading) using an original mapping of a work vector storing q original mapping numbers used for each element, and m bytes in the ciphertext data. A vector having a predetermined number of elements is generated. Conversely, when decrypting a ciphertext, when a secret key is given, a display start position on a random number table is determined. Next, from the ciphertext data, m
Each time a vector of byte × predetermined number of elements is read, a value is read from the random number table and the reading mechanism and used (p +
q) Determine the numbers of the original maps. The vector of m bytes × predetermined number of elements in the ciphertext data is first converted (list vector loading) by using the inverse mapping of the work vector stored in the reverse order of q original mapping numbers used for each element. Is converted by multiplication with the inverse matrix of order m, and finally,
The p original mapping numbers used for each element are converted (list vector loaded) using the inverse mapping of the work vector stored in reverse order, and a vector of m bytes in the plaintext data × a predetermined number of elements is generated. .

Therefore, a person who attempts to decrypt the ciphertext according to the present invention without knowing the secret key cannot know the display start position on the random number table and the reading mechanism from the known plaintext attack. In addition, it is not possible to analyze by taking a difference from a combination of a known plaintext and a plaintext or a selected combination of a plaintext and a plaintext. Further, it is practically impossible to repeat the selective plaintext attack and try a brute force of m bytes of plaintext. Also, it is not possible to try a brute force secret key. In addition, it is not possible to try the indirect index array by brute force or the brute force permutation of the original mapping of the indirect index array. As described above, according to the present invention, when encrypting data, a long-period random number table,
A mechanism for changing the permutation of the indirect index array by a random number,
By using a composite mapping that sandwiches the integration with the constant series matrix in the conversion using the indirect index array, the known plaintext attack and the selected plaintext attack can be made virtually impossible.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a mapping mechanism used in an embodiment of the present invention will be briefly described with reference to the drawings.

In post-modern cryptography, it is essential that characters in a target range be associated with numerical values by some method. The range of target characters varies depending on the type of communication channel assumed. The correspondence between characters and numeric values also varies depending on the encryption method used.

FIG. 1 shows an example in which characters and numerical values are associated with each other in a mapping.
2 illustrates a correspondence between a character and a numerical value. The example shown in FIG. 1 shows an example in which 89 types of characters including alphabetic characters, numerals, and some symbols are associated with integer values of 0 to 88. In the following description, 89 types of characters are assumed to be the same as the elements of the cosets modulo 89, and the cosets modulo 89 are denoted as Z | 89 (see equation (1)). Z | 89 = {0, 1,..., 88} (1) In addition, if the modulus of the coset is not a prime number, that is, if the number of target character types is not a prime number, special Attention is necessary.

Next, the mechanism of mapping using the indirect index array used in the present invention will be described. FIG.
FIGS. 4A and 4B illustrate a mechanism of mapping using an indirect index array according to an embodiment of the present invention, wherein FIG. 4A illustrates mapping using an index and an indirect index array, FIG.
(C) shows an example of the combined mapping. FIG.
As shown in (a), an index x is converted to an indirect index array c (j).
When converted by (j = 0 to 88), y = c (x).
The index array x (i) (i = 0 to 3) is replaced with an indirect index array c
When converted by (j) (j = 0 to 88), the array y (i) =
c (x (i)). As shown in FIG. 2B, the index array (50, 60, 70, 80) is replaced with the indirect index array (2
(No. 0), 3, ..., 52 (No. 50), ..., 62 (60
, 88 (86), 0, 1 (88)), it becomes an array (52, 62, 72, 82). Further, as shown in FIG. 2C, the index array (50, 60,
70, 80) by the indirect index array (2 (0th), 3,...,
52 (No. 50), ..., 62 (No. 60), ..., 88 (86
), 0, 1 (88), and indirect index arrays (1 (0), 2, 3, ..., 53 (52), ...,
63 (No. 62), ..., 83 (No. 82), ..., 88, 0
(No. 88)), the array (53, 63, 73,
83).

In the following description of the embodiment of the present invention, an indirect index array is an array of elements of Z | 89 arranged one by one in an arbitrary order. That is, c (j)
When (j = 0 to 88) is an indirect index array, the relationships shown in Expressions (2) and (3) hold. ∀j∈Z | 89 c (j) ∈Z | 89 (2) ∀i, j∈Z | 89 i ≠ j → c (i) ≠ c (j) (3) One indirect index array , Or an array of any number of elements, can be represented as a bijective mapping, replacing another character. Assuming that the character to be converted is x,
Naturally, x∈Z | 89. This is called the indirect index array c
The destination of the mapping converted in (j) is c (x). The indirect index array can also transform some original arrays. For example, if an array of four characters to be converted is x (i) (i = 0 to 3), naturally, 0 ≦ i ≦
For each i in 3, x (i) ∈Z | 89. The destination of the mapping obtained by converting this with the indirect index array c (j) is c (x (i)).

In the following description, the original or original array to be converted is referred to as an index or an index array. This is because the element to be converted is an index indicating the destination as a subscript of the indirect index array. The composite mapping of the mapping by the indirect index array can be represented by the indirect index array. Indirect index arrays c1 (j), c2 (j) (i = 0 to 8
8), the index x is first converted by c1 (j),
Then, the destination of the composite map converted by c2 (j) is c
2 (c1 (x)). A composite mapping that performs conversion by c2 (j) following conversion by c1 (j) is represented by an indirect index array c2 (c1 (j)).

FIG. 3 shows the inverse mapping of the mapping by the indirect index array according to the embodiment of the present invention. FIG. 3A shows the description of the indirect index array representing the inverse mapping.
(B) shows an example of an indirect index array representing an inverse mapping, respectively.

As shown in FIG. 3A, the index array x
(I) (i = 0 to 88) is converted to an indirect index array c (j) (j =
0 to 88) to obtain an array (0, 1,..., 88), the mapping expressed by regarding the array x (i) (i = 0 to 88) as an indirect index array is represented by an array c It is a reverse mapping of the mapping represented by (j).

As shown in FIG. 3B, the index array (8
7,88,0 (2nd), 1, ..., 48 (50th), ...,
58 (No. 60), ..., 85 (No. 87), 86 (88
)) Is replaced with an indirect index array (2 (0), 3,..., 52
(No. 50), ..., 62 (No. 60), ..., 88 (86
), 0, 1 (No. 88)), the array (0,
1, 2, ..., 87, 88).

There is always one inverse mapping in the mapping by the indirect index array. Arbitrary indirect index array c (j) (j =
0 to 88), only one index array x (j) (j
= 0-88), and c (x (j)) = (0, 1,
..., 88). This is because, by definition, an indirect index array is one in which elements of Z | 89 are arranged one by one. Since (0, 1,..., 88) is an identity mapping, in the above case, x (j) is an indirect index array representing an inverse mapping of the conversion by c (j).

FIGS. 4A and 4B show the mechanism of mapping by matrix multiplication in the embodiment of the present invention, wherein FIG. 4A shows a description of mapping by matrix multiplication, and FIG. 4B shows mapping by matrix multiplication. Are respectively shown. FIG.
As shown in (a), an index array x (i) (i = 0 to 3)
Is converted by multiplication with a matrix f (i, j) (i, j = 0 to 3) to obtain an array shown in Expression (4).

[0028]

(Equation 1)

As shown in FIG. 4B, the array (1, 2, 2,
(3, 4) is converted by the product of the matrix shown in equation (5),
The index array (1, 3, 4, 5) represented by Expression (6) is obtained.

[0030]

(Equation 2)

[0031]

(Equation 3)

The mechanism of mapping by multiplication of matrices is as follows. Now, x (i) is an array in which some elements of Z | 89 are arranged, for example, an array having four elements. Fourth-order square matrix f (i, j) (i, j = 0
３3), the product fx of the matrix modulo 89 and the vector is an array in which four elements of Z | 89 are arranged. n
The following square matrix integration is a mapping from an array in which four elements of Z | 89 are arranged to an array in which four elements of Z | 89 are arranged.

FIG. 5 shows the mechanism of the inverse mapping based on the integration of the inverse matrix in the embodiment of the present invention.
(B) shows an example of an inverse matrix representing an inverse mapping, respectively. As shown in FIG. 5A, the matrix g (i, j) (i,
j = 0-3) and a matrix f (i, j) (i, j = 0-3)
Is a unit matrix, the conversion by integration with the matrix g is an inverse mapping of the conversion by integration with the matrix f. FIG.
As shown in (b) and equation (7), when the product of matrix g and matrix f is a unit matrix,

[0034]

(Equation 4)

The conversion by integration with the matrix g is an inverse mapping of the conversion by integration with the matrix f. The mechanism of the inverse mapping by the integration of the inverse matrix is as follows. Now, the matrix f
On the other hand, when the inverse matrix g exists, the mapping based on the integration of the matrix g represents the inverse mapping of the mapping based on the integration of the matrix g.

The inverse matrix does not always exist for any matrix f. In particular, care must be taken when choosing a non-prime number as the modulus of the coset. In the embodiment of the present invention, a combination of the constant coefficient matrix f and the constant coefficient inverse matrix g is used. When an inverse matrix exists for the matrix f, the matrix f is obtained by arranging four elements of Z | 89 from:
This is a bijective mapping to an array in which four elements of Z | 89 are arranged.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The description will be specifically made using an embodiment. FIG. 6 is a diagram for explaining items determined and distributed before the start of use in the common key encryption or decryption method according to the first embodiment of the present invention. FIG. 4 is a diagram for explaining procedures of encryption and decryption in the method of the embodiment. In this example, the random number table and the reading mechanism 1 shown in FIG.
An indirect index array 2 representing the original maps 0 to 67;
7, an indirect index array 3 representing an inverse mapping, a fourth-order matrix f4 of constant coefficients, and an inverse matrix g5 of f are separately determined and distributed before starting to use the common key encryption or decryption method. Shall be

The random number table and the reading mechanism 1 are equipped with a 10-stage random number table containing random integer values. The length of each row of the random number table is 89, 83, 79,.
As shown in FIG. 7, they are relatively prime. The reading mechanism starts reading from an appropriate position, reads one display value from the current display position of each stage, and reads out one display value.
The weighted sums b1 to b10 of the display values of each stage of the types are collected, and the remainder c of each weighted sum modulo 68
1 to c10 are calculated. The weight in this case may be determined appropriately, and a weighted sum is obtained for each type of weight. The reading mechanism shifts the display position in each stage one by one to the right each time reading is performed. The period of this random number table is Π (89, 83,..., 47), and is 1.8.
× ¹⁰ about ^{1 8.} The indirect index array 2 representing the original mappings 0 to 67 is obtained by arranging 68 indirect index arrays.
It is desirable to create the contents of each indirect index array using an appropriate random number. Also, the number of indirect index arrays is, for example, as described later, in the case of an attack method of trying a brute force combination of original maps and in the case of an attack method of trying a brute force display position of a random number table. An appropriate value may be selected in consideration of the number of trials and the execution time.

The indirect index array 3 representing the inverse mapping of the original mappings 0 to 67 is obtained by arranging the indirect index array representing the inverse mapping for each array of the indirect index array 2. In order to create the indirect index array 3, the operation of sorting 89 elements is performed only 68 times. The fourth order matrix f of the constant series and the inverse example g of f are appropriate matrices selected such that one inverse matrix exists. Of course, a unit matrix should not be selected for the fourth-order matrix f of the constant series, but a sparse matrix such as that shown in FIG. 5B is also not preferred, and it is desirable to select a dense matrix. The order of the matrix is not limited to the fourth order, and can be arbitrarily selected, for example, a multiple of the fourth order. In this case, the order of the matrix is equal to the number of bytes of the character string handled in one process. It is necessary to do so.

Next, a procedure for encrypting a plaintext and decrypting a ciphertext by the method of this example will be described with reference to FIGS. First, the sender specifies the secret key 6 to determine the starting position of each stage of the random number table from the secret key 6. When the length of the secret key 6 is specified from, for example, 89 types of characters, it is recommended to input 10 bytes or more. From the secret key 6, weighted sums a1 to a10 with 10 arbitrary weights are collected,
The remainder modulo 89, the remainder modulo 83, respectively
…, Calculate the remainder modulo 47, and in the first row of the random number table,
The display start position of the second tier,..., Tenth tier is determined (procedure S1). First, the character string 7 of 4 bytes is sequentially extracted from the plain text data (step S2). Each time the character string is extracted, the value is read out from the random number table and the reading mechanism 1, and the numbers c1 to c5 of the original mappings to be used , C6 to c10 are determined.

Next, from the indirect index array representing the original mapping 0 to the indirect index array representing the original mapping 67 shown in FIG.
Then, the array of number is taken out, and an indirect index array d1 representing these composite maps is created (step S3). Similarly, arrays c6 to c10 are extracted from the indirect index array 2, and an indirect index array d2 representing a composite map of these is created (procedure S
4). Then, the 4-byte character string in the plaintext data is first converted by the indirect index array d1 (step S5), and then the converted character string is converted by multiplication with the matrix f (step S5).
6) Further, the character string of this conversion result is stored in the indirect index array d.
2 (step S7), and stores the character string resulting from the conversion as a 4-byte character string 8 in the ciphertext data (step S7).
8). Next, the display position of each row of the random number table is moved to the right one by one, the next 4-byte character string is read from the plaintext data, and the same processing as above is repeated thereafter. Regarding the processing of the end portion of the plaintext data of less than 4 bytes, for example, appropriate data may be padded and adjusted so as to be a multiple of 4 bytes, which is irrelevant to the nature of the present invention.

The above-mentioned secret key 6 is also used when the recipient decrypts the encrypted text thus generated.
As in the case of the encryption, the display start position of each row of the random number table is determined. Each time a 4-byte character string is extracted from the ciphertext data, the numbers c1 to c10 of the original maps are obtained in the same manner as in the encryption.
Is calculated. Next, an array of inverse maps c10 to c6 is extracted from the indirect index array representing the inverse mapping of the original mapping 0 to the indirect index array representing the inverse mapping of the original mapping 67 shown in 3 and represents a composite mapping of these. An indirect index array e2 is created (procedure S9). At this time, it should be noted that at the time of encryption, c
6, c7,..., C10, whereas the inverse map is synthesized in the order of c10, c9,.

Next, similarly, an array of inverse mappings of c5 to c1 is extracted from the indirect index array 3, and an indirect index array e1 representing these composite maps is created (step S10). It should be noted that, in this case as well, the composition is performed in the reverse order of the encryption. Either step S9 or step S10 may be performed first. Then, the 4-byte character string 8 in the ciphertext data is first converted by the indirect index array e2 and the procedure S
11) Next, the character string of the conversion result is converted by multiplication with the inverse matrix g (step S12), and the character string of the conversion result is further converted by the indirect index array e1 (step S13). Is stored as a 4-byte character string in the plaintext data (step S14). The processing of the end portion of the encrypted data that is less than 4 bytes may be performed in the same manner as in the case of encrypting the plaintext data.

In the following, the possibility of deciphering the ciphertext by the common key encryption method of this example without knowing the secret key will be examined. Now, the attacker determines that the encryption method other than the secret key, that is, the random number table and the reading mechanism 1, and the indirect index array 2 representing the original maps 0 to 67.
And an indirect index array 3 representing an inverse mapping of the original mappings 0 to 67;
Assuming that the quaternary matrix f4 of the constant coefficient and the inverse matrix g5 of f have been obtained, in this case, the attacker does not know the secret key 6, so that the display on the random number table and the reading mechanism 1 starts. The location cannot be determined directly.

Assuming that the attacker has obtained a combination of plaintext and ciphertext for, for example, the first four bytes, in this case, which and which of the original maps 0 to 67 are c
Since it is not known that the indices are selected as 1 to c10, the indirect index arrays d1 and d2 are mappings unknown to the attacker.
Here, the problem to be solved by the attacker is as follows: “A known 4-byte character string is added to an unknown indirect index array d1 and a known matrix f. Find the indirect index arrays d1 and d2 in the case of a sequence. Find the display position on the random number table. "However, this problem cannot be solved by an analytical method.

Further, the attacker can select a combination of a known plaintext and a plaintext or a selected combination of a plaintext and a plaintext,
Assuming that the analysis is performed by taking the difference, the secret sentence of the present invention is a mapping that is not related to the linear property of the conversion by the indirect index array, and is a form sandwiching the conversion by the integration of the matrix. Therefore, differential analysis is impossible.

Assume that the attacker obtains a large number of combinations of plaintext and encrypted text for the first four bytes, for example, and tries to solve the problem by creating a correspondence table. if simply calculated, it must obtain a combination of degree 89 ⁴ i.e. 62 million or more. The known plaintext attack is established when, for some reason, the plaintext is known and the plaintext obtained by using the same secret key can encrypt the plaintext. It is virtually impossible to expect to use the same secret key a million times.

It is also assumed that the attacker attempts a selective plaintext attack as described below. That is, the whole sentence is constant 4
Plain text data that is a repetition of a byte string, such as "comp", "entr", "conc",
"Symm", "able", "then", "tha
Create plain text data consisting of repeating 4-byte character strings such as "n" and "here". Then, a character string that appears to appear frequently in the plaintext is tried one after another, and the other party is encrypted with the same secret key to obtain a ciphertext. Similarly, plaintext data corresponding to the case where the above-mentioned character string appears at the 1st byte, 2nd byte, or 3rd byte with respect to an integer multiple of 4 bytes is created, and the same secret key is sent to the other party. To obtain the encrypted text.

That is, four types of plaintext data are selected for each character string that appears to appear frequently. Then, when a correspondence table is created and compared with the target ciphertext, if a certain character string appears at a certain position in the target ciphertext, the plaintext at that position is found. However, in order for attacks using this technique to be meaningful, no less than 5
It is considered that zero or more types of character strings x about four or more trials are essential. Selective plaintext attack is to encrypt the plaintext selected by the attacker with the secret key using some form of fraud,
It is established by obtaining the secret sentence. However, the fact that 200 or more selective plaintext attacks can be launched cannot be considered in reality. If you can do that, it would be much easier to get your secret key.

Also, the attacker can use the random number table and the readout mechanism 1
It is assumed that the brute force of the display start position is tried using As described above, the cycle of the random number table is about 1.8 × 10 ¹⁸ . Therefore, even if there is a computer or dedicated hardware capable of performing 100 million trials per second, this trial will take 570 years or more.

It is also assumed that the attacker has attempted a brute force secret key. Assuming that the sender uses a character string of 10 bytes as the length of the secret key and only the length of “10 bytes” is known, a possible combination is 31
It is about × 10 ¹⁸ . Therefore, even if there is a computer or dedicated hardware capable of performing 100 million trials per second, this trial will take 9800 years or more.

Also, if the attacker determines that the indirect index arrays d1, d2
, The factorial of 89 is 1
6 × 10¹³⁵Indirect index array itself
It's absolutely impossible to try each possibility
It is good. Therefore, among the original maps 0 to 67, 10
Possible combinations are selected and synthesized.
A brute force attempt will be made, but possible permutations are 68
¹⁰And 2 × 10 ¹⁸Will be about
The same condition would take over 600 years.

The method of this example is equivalent to “a combination of a polytable encryption having a period of almost infinite length and a spelling / replacement encryption” as compared with a classic encryption method.
In the future, if the execution speed that can be realized by a computer or dedicated hardware is significantly improved and brute force as described in each of the above examples becomes possible, the number of stages in the random number table and the width of each stage, and the composite mapping It can be dealt with only by quantitatively increasing the number of indirect index sequences to be used, and qualitative modification of the encryption method itself is not required.

As described above, according to the common key encryption / decryption method of this example, a long-period random number table, a mechanism for changing the permutation of the indirect index array by using random numbers, and a constant coefficient Since it has a composite map in which the matrix and the multiplication are interposed, the known plaintext attack and the selected plaintext attack can be made virtually impossible.

Second Embodiment FIG. 9 is a diagram for explaining items to be determined and distributed before the start of use in a common key encryption or decryption method according to a second embodiment of the present invention. FIG. 11 is a view for explaining the procedure of encryption and decryption in the method of the embodiment. In this example, the random number table and the reading mechanism 11 shown in FIG.
And an indirect index array 12 representing the original mappings 0 to 67, an indirect index array 13 representing the inverse mapping of the original mappings 0 to 67, a fourth order matrix f14 of constant coefficients, and an inverse matrix g15 of f are a common key. It shall be determined and distributed separately before the use of the encryption or decryption method is started.

Here, a random number table and readout mechanism 11, an indirect index array 12 representing the original mappings 0 to 67, an indirect index array 13 representing the inverse mapping of the original mappings 0 to 67, and a quaternary matrix f of constant coefficients
The inverse matrix g15 of 14 and f is a random number table and a readout mechanism 1, an indirect index array representing the original mappings 0 to 67, and an indirect index array representing the inverse mapping of the original mappings 0 to 67, respectively, shown in FIG. 3, the same as the inverse matrix g5 of the quaternary matrices f4 and f of the constant coefficients, and a detailed description thereof will be omitted below.

Next, a procedure for encrypting a plaintext and decrypting a ciphertext by the method of this example will be described with reference to FIGS. First, the procedure for determining the starting position of each stage of the random number table from the secret key 16 by designating the secret key 16 by the sender is the same as that of the first embodiment shown in FIGS. (Procedure P1). First, a vector 17 of 4 bytes × 256 elements is extracted from the plaintext data (procedure P2), and the random number table and the reading mechanism 11
56 readings and the original mapping numbers c1 to c to be used
10 is calculated, and the original mapping number c1 used for each element
To c5 are stored in the stored work vector 18 (procedure P
3) Store the original mapping numbers c6 to c10 used for each element in the work vector 19 (step P4). Note that the number of bytes extracted from the plaintext data is not limited to 4 bytes as in the case of the first embodiment, and the relationship between this and the order of the matrix is also the same. Also, the number of elements is 256
Not limited to elements, for example, 512 elements may be used.

Next, each element of the vector 17 of 4 bytes × 256 elements in the plain text data is included in each element of the work vector 18 storing the original mapping numbers c1 to c5 used for each element. Is converted using the original mapping pointed to by (step P5). This operation is called a list vector load, and can be executed at high speed by a computer having a vector pipeline operation unit. Next, each element of the vector obtained by the above operation is converted by integration with the matrix f (procedure P6). This operation is a linear operation, and can be executed at high speed by a computer having a vector pipeline operation unit. Next, each element of the vector obtained by the above operation is
Conversion is performed using the original mappings indicated by the original mapping numbers c6 to c10 included in each element of the work vector 19 storing c6 to c10 used for each element (procedure P
7). This operation is a list vector load similarly to the above, and can be executed at high speed by a computer having a vector pipeline arithmetic unit. Then, each element of the vector of the conversion result is stored in the ciphertext data as a vector of 4 bytes × 256 elements in the ciphertext data (procedure P8).

The decryption of the thus-prepared ciphertext can be performed by the same procedure using the inverse mapping and the inverse matrix, as in the first embodiment. As in the case of the encryption, the display start position of each row of the random number table is determined.
Each time the 4-byte × 256-element vector 20 is extracted from the ciphertext data, the random number table and the reading mechanism 11
Number of times of reading and numbers c1 to c10 of original maps to be used
Is calculated, and the original mapping number c10 used for each element is calculated.
To c6 are stored in the stored work vector 21 (procedure P
9) The original mapping numbers c5 to c1 to be used for each element are stored in the work vector 22 which stores them (procedure P10). Either procedure P9 or procedure P10 may be performed first.

Next, each element of the vector 20 of 4 bytes × 256 elements in the ciphertext data is stored in each of the elements of the work vector 21 storing the original mapping numbers c10 to c6 used for each element. Conversion (list vector loading) is performed using the inverse mapping of the original mapping indicated by c6 (procedure P11), and each element of the 4-byte × 256-element vector resulting from the conversion is integrated with the inverse matrix g of the matrix f. Conversion (linear operation) (procedure P12), 4 bytes × 256 of the conversion result
Each element of the element vector is transformed using the inverse mapping of the original mapping pointed to by c5 to c1 included in each element of the work vector 22 storing the original mapping numbers c5 to c1 used for each element (list Vector loading) (procedure P
13) Store the 4-byte × 256-element vector of the conversion result in the plaintext data as a 4-height × 256-element vector in the plaintext data (procedure P14). The processing of the end portion of the encrypted data that is less than 4 bytes may be performed in the same manner as in the case of encrypting the plaintext data.

As described above, according to the common key encryption method of this example, a long-period random number table, a mechanism for changing the permutation of the indirect index array by random numbers, and a constant coefficient matrix by conversion using the indirect index array are used. Since it has a composite map sandwiching the multiplication, the known plaintext attack and the selected plaintext attack can be made virtually impossible.

It is virtually impossible to perform a known plaintext attack and a selective plaintext attack on a ciphertext by the common key encryption method of this example. The reason is the same as that described in the first embodiment, and a detailed description thereof will be omitted.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there may be changes in the design without departing from the gist of the present invention. Even this is included in the present invention. For example, when the present invention is realized by software, an appropriate computer system such as a general-purpose machine, a workstation, a personal computer, or the like is provided as hardware, and a program for executing the method of the present invention is provided therein. Can be easily realized. Furthermore, by preparing such a program in advance in a state in which the program is recorded on a medium of any format that is readable by the processing device, the same method can be universally realized when a similar system is provided. Can be.

[0064]

As described above, according to the present invention, a long-period random number table, a mechanism for changing the order of the indirect index array by random numbers, and integration of a constant coefficient by conversion using the indirect index array are interposed. Since it has a composite map of the form, it is virtually impossible to make known plaintext attacks and selective plaintext attacks.
It is possible to provide a storage medium that records a common key encryption or decryption program while realizing a common key encryption or decryption method.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a case where a character is associated with a numerical value in a mapping.

FIG. 2 is a diagram illustrating a mechanism of mapping using an indirect index array according to an embodiment of the present invention;

FIG. 3 is a diagram showing a reverse mapping of a mapping by an indirect index array according to the embodiment;

FIG. 4 is a diagram showing a mechanism of mapping by multiplication of matrices in the embodiment.

FIG. 5 is a diagram showing a mechanism of inverse mapping by multiplication of an inverse matrix in the embodiment.

FIG. 6 is a diagram for explaining items to be determined and distributed before the start of use in the common key encryption or decryption method according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating the procedure of encryption and decryption in the method of the embodiment.

FIG. 8 is a diagram illustrating the procedure of encryption and decryption in the method of the embodiment.

FIG. 9 is a diagram for explaining items to be determined and distributed before starting use in a common key encryption or decryption method according to a second embodiment of the present invention.

FIG. 10 is a diagram illustrating the procedure of encryption and decryption in the method of the embodiment.

FIG. 11 is a diagram illustrating the procedure of encryption and decryption in the method of the embodiment.

[Explanation of symbols]

1,11 random number table and readout mechanism 2,12 indirect index array representing original mapping 0-67 3,13 indirect index array representing inverse mapping of original mapping 0-67 4,14 fourth order matrix of constant coefficient 5,15 constant Inverse matrix of coefficient fourth order matrix 6, 16 Secret key 7 4-byte character string in plaintext data 8 4-byte character string in plaintext data 17 Vector of 4 bytes x 256 elements in plaintext data 20 4 bytes x 256 element vector

Claims (8)

[Claims] 1. A long-period random number table, a read-out mechanism for calculating (p + q) original mapping numbers based on display values of the random number table, an indirect index array representing each original mapping, and a constant coefficient m The following matrix is prepared in advance, and when a secret key is designated, a display start position of the random number table is determined from the secret key, and each time an m-byte character string is extracted from plaintext data, the random number table and the reading mechanism are read out. Calculating the numbers of the (p + q) original mappings, and the first indirect index array representing the composite mapping of the original mappings indicated by the p original mapping numbers in the (p + q) original mapping numbers And a second indirect index array representing a composite map of the original mappings indicated by the q original mapping numbers in the (p + q) original mapping numbers, and a character string extracted from the plaintext data. Is converted by the first indirect index array, and then The character string resulting from the conversion is converted by multiplication with the m-th order matrix of the constant coefficient, and the character string obtained by converting the character string resulting from the conversion with the second indirect index array is used in the ciphertext data. By repeating the process of storing the m-byte character string in the ciphertext data while reading the m-byte character string from the plaintext data while shifting the display position of each row of the random number table one by one, A common key encryption method, comprising: 2. A long-period random number table, a reading mechanism for calculating (p + q) original mapping numbers based on display values of the random number table, an indirect index array representing a reverse mapping of each original mapping, and a constant When an inverse matrix of an m-th order matrix of coefficients is prepared in advance, and a secret key is designated, after determining the display start position of the random number table from the secret key, every time a m-byte character string is extracted from the ciphertext data, The number of the (p + q) original mappings is calculated by the random number table and the reading mechanism, and when the original mappings indicated by the p original mapping numbers in the (p + q) original mapping numbers are encrypted, A first indirect index array representing a composite map of an inverse mapping of an array in the reverse order to the above, and an array in an order reverse to that at the time of encryption of the original mapping indicated by q original mapping numbers in the (p + q) original mapping numbers And a second indirect index array representing a composite map of the inverse map of The character string extracted from the memorized sentence data is converted by the second indirect index array, and then the converted character string is converted by multiplication with the inverse matrix of the m-order matrix of the constant coefficient. A process of storing a character string obtained by converting the character string of the conversion result using the first indirect index array into the plaintext data as a character string of m bytes in the plaintext data is performed by using m bytes of the ciphertext data. A common key decryption method, wherein a ciphertext is decrypted by repeating the display position of each row of the random number table one by one in a direction opposite to that in the encryption at every reading of the character string. . 3. A long-period random number table, a reading mechanism for calculating (p + q) original mapping numbers based on display values of the random number table, an indirect index array representing each original mapping, and a constant coefficient m The following matrix is prepared in advance, and when a secret key is designated, a display start position of the random number table is determined from the secret key, and every time a vector of a predetermined number of m bytes is extracted from plaintext data, By the random number table and the reading mechanism,
By reading out the element several times and calculating the numbers of the (p + q) original mappings, the (p +
q) The original mapping numbers of the original mapping numbers are stored in the first work vector, and the q original mapping numbers of the (p + q) original mapping numbers used for each element are stored in the first working vector. 2
, And converts each element of the vector extracted from the plaintext data using an original mapping indicated by the p original mapping numbers included in each element of the first work vector. Is converted by multiplying each element of the vector of the conversion result with the m-th order matrix of the constant coefficient, and further, each element of the vector of the conversion result is included in each element of the second work vector, q The process of storing a vector obtained by converting using the original mappings indicated by the original mapping numbers into the ciphertext data as a vector of a predetermined number of m-byte elements in the ciphertext data, A common key encryption method, characterized in that plain text encryption is performed by repeating the display position of each row of the random number table one by one every time a vector of a predetermined number of elements of bytes is read. 4. A long-period random number table, a reading mechanism for calculating (p + q) original mapping numbers based on display values of the random number table, an indirect index array representing inverse mapping of each original mapping, and a constant When an inverse matrix of an m-th order matrix of coefficients is prepared in advance and a secret key is designated, a display start position of the random number table is determined from the secret key. Every time a vector is taken out, the random number table and the reading mechanism
By reading out the element several times and calculating the (p + q) original mapping numbers, the (p +
q) The p original mapping numbers in the original mapping numbers are stored in the first work vector in the reverse order of the encryption, and the q number in the (p + q) original mapping numbers used for each element. Are stored in the second work vector in the reverse order of the time of encryption in the second work vector, and each element of the vector extracted from the ciphertext data is replaced with the q number of elements included in each element of the second work vector. The conversion is performed using the inverse mapping of the original mapping indicated by the original mapping number, and then each element of the vector of the conversion result is converted by multiplication with the inverse matrix of the m-th order matrix of the constant coefficient. Are converted using the inverse mapping of the original mappings indicated by the p original mapping numbers included in each element of the first working vector, and m bytes of the plaintext data are obtained. Store in plaintext data as a vector of a predetermined number of elements The process is repeated by shifting the display position of each row of the random number table one by one in a direction opposite to that at the time of encryption every time a vector of a predetermined number of m-byte elements is read from the ciphertext data. A common key decryption method characterized by decrypting a sentence. 5. A computer-readable recording medium having recorded thereon a program for executing the common key encryption method according to claim 1, wherein (p + q) based on a long-period random number table and a display value of the random number table. Readout mechanism for calculating the number of original mapping numbers, an indirect index array representing each original mapping, and an m-th order matrix of constant coefficients are prepared in advance, and when a secret key is specified, the random number table of the random number table is determined from the secret key. After determining the display start position, each time an m-byte character string is extracted from the plaintext data, the (p +
calculating the numbers of q) original mappings, a first indirect index array representing a composite mapping of the original mappings indicated by p original mapping numbers in the (p + q) original mapping numbers, and and a second indirect index array representing a composite map of the original mappings indicated by the q original mapping numbers in the (p + q) original mapping numbers, and converting the character string extracted from the plaintext data into the first And then convert the character string of the conversion result by multiplication with the m-th order matrix of the constant coefficient, and further convert the character string of the conversion result by the second indirect index array. The process of storing the obtained character string in the ciphertext data as a m-byte character string in the ciphertext data is performed by reading the m-byte character string from the plaintext data every time the m-byte character string is read out. The program that encrypts plaintext by repeating A storage medium storing a common key encrypted program, characterized by recording a. 6. A computer-readable recording medium storing a program for executing the common key decryption method according to claim 2, wherein (p + q) based on a long-period random number table and a display value of the random number table. A readout mechanism for calculating the number of original mappings, an indirect index array representing an inverse mapping of each original mapping, and an inverse matrix of an m-th order matrix of constant coefficients are prepared in advance. After determining the display start position of the random number table from the key, every time an m-byte character string is extracted from the ciphertext data, the random number table and the reading mechanism calculate the numbers of the (p + q) original maps. , A first indirect index array representing a composite map of a reverse mapping of an order reverse to that at the time of encryption of the original mappings indicated by the p original mapping numbers in the (p + q) original mapping numbers, and (p + q Q) elements in the) original mapping numbers A second indirect index array representing a composite mapping of the inverse mapping in the reverse order to that of the encryption of the original mapping indicated by the mapping number, and forming the character string extracted from the ciphertext data into the second The conversion is performed by an indirect index array, and then the converted character string is converted by multiplication with the inverse matrix of the m-th order matrix of the constant coefficient, and the converted character string is further converted by the first indirect index array. The character string obtained by
The process of storing the plaintext data as a byte character string is such that the display position of each row of the random number table is shifted one by one in the direction opposite to that at the time of encryption every time the m-byte character string is read from the ciphertext data. A storage medium storing a common key decryption program characterized by recording a program for decrypting a ciphertext by repeating the above process. 7. A computer-readable recording medium having recorded thereon a program for executing the common key encryption method according to claim 3, wherein (p + q) based on a long-period random number table and a display value of the random number table. Readout mechanism for calculating the number of original mapping numbers, an indirect index array representing each original mapping, and an m-th order matrix of constant coefficients are prepared in advance, and when a secret key is specified, the random number table of the random number table is determined from the secret key. After the display start position is determined, every time a vector of a predetermined number of m bytes of elements is extracted from the plaintext data, the random number table and the reading mechanism read out the elements several times and obtain the (p + q) original maps. Numbers are calculated, and p original mapping numbers in the (p + q) original mapping numbers used for each element are set to the first.
, And the q original mapping numbers in the (p + q) original mapping numbers used for each element are stored in the second working vector, and each element of the vector extracted from the plaintext data is stored. Is converted using the source mappings indicated by the p source mapping numbers included in each element of the first working vector, and then each element of the vector of the conversion result is converted into an m-th order matrix of the constant coefficient. , And each element of the vector of the conversion result is obtained by converting using the original mapping indicated by the q original mapping numbers included in each element of the second work vector. The process of storing a vector in the ciphertext data as a vector of a predetermined number of m-byte elements in the ciphertext data is performed by reading the random number table every time a vector of a predetermined number of m-byte elements is read from plaintext data. Display of each column of By repeated while shifting the location one by one, the storage medium in which a common key encryption program characterized by recording a program for encrypting plaintext. 8. A computer-readable recording medium on which a program for executing the common key decryption method according to claim 4 is recorded, based on a long-period random number table and a display value of the random number table (p + q). A readout mechanism for calculating the number of original mappings, an indirect index array representing an inverse mapping of each original mapping, and an inverse matrix of an m-th order matrix of constant coefficients are prepared in advance. After determining the display start position of the random number table from the key, every time a vector of a predetermined number of m bytes of elements is extracted from the ciphertext data, the random number table and the reading mechanism read out the element several times and execute the ( The numbers of (p + q) original mappings are calculated, and the p original mapping numbers of the (p + q) original mapping numbers used for each element are stored in the first work vector in the reverse order of the encryption. Along with Q original mapping numbers in the (p + q) original mapping numbers used for each element are stored in the second working vector in the reverse order of the encryption, and each element of the vector extracted from the ciphertext data is stored. , Using the inverse mapping of the q original mappings contained in each element of the second working vector, and then converting each element of the vector of the conversion result to the constant coefficient m Inverse transformation of the original mapping indicated by the p original mapping numbers included in each element of the first working vector, wherein each element of the vector resulting from the transformation is converted by integration with the inverse matrix of the next matrix Is stored in the plaintext data as a vector of a predetermined number of m-byte elements in the plaintext data, and a process of storing a vector of a predetermined number of m-byte elements from the ciphertext data is performed. For each read, each stage of the random number table By repeated while shifting the shown position one by one during encryption and backward, storage medium storing a common key decryption program characterized by recording a program for decoding the Kurabun.