JPS5843743B2 - Encryption method - Google Patents

Description

[Detailed Description of the Invention] The present invention provides encryption of data processed by a computer, etc.
Regarding decryption of the encrypted data.

Well-known encryption methods include the substitution method, which uses a password or key to perform an operation that is inverse to the input data, and performs the encryption process; and the substitution method, which performs the encryption process by changing the order within a block of data. There are transliteration methods, etc.

However, using just one of these methods can break the code, and combining several methods makes it almost impossible to guess the key or password.

Therefore, an encryption process that can withstand code breaking is
The disadvantage is that the system becomes complex.

The object of the present invention is to perform M-sequence (Maximum Lengt
hI near Shift register Se
By using a random data generation circuit consisting of a shift register and a logic feedback circuit that generates a pseudo-random number sequence called a quiuce for encryption processing, it is effective enough to break codes, and is simple and inexpensive. The purpose of the present invention is to provide a method for performing cryptographic processing.

In the encryption process, the encryption key usually determines the operation.

For example, EXCLNSIVE- of encryption key and input data
An OR operation is performed, or one block of input data is raised to the power of an encryption key, and the remainder with another encryption key is used as encrypted data.

In the present invention, the cryptographic key does not determine the operation, but rather determines the initial state of the random data generation circuit.

This invention will be explained in detail below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of decoding according to the present invention, FIG. 2 is a block diagram of an embodiment of decoding according to the present invention, and FIG. 3 is an explanatory diagram of the present invention.

In FIG. 1, 11 is an input register, 12 is a random data generation circuit, 13 is a key register, 14 is a function generation circuit, and 15 is an exclusive OR operation circuit.

In FIG. 2, 21 is an input register, 22 is a random data generation circuit, 23 is a key register, 24 is a function generation circuit, and 25 is an exclusive OR operation circuit.

In FIG. 3, b is an explanatory diagram of encryption, and b is an explanatory diagram of decryption.

In FIG. 3, S7. S2...5n-1゜Sn
constitutes a shift register.

In FIG. 1, first, the value of the encryption key register 13 is input to the function generation circuit 14 to generate binary data and initialize the random data generation circuit 12.

Next, the input data, that is, the plain text, is stored in the one-person college register 11.

Then, the data in the input register 11 is passed through the random data generation circuit 12, and the exclusive OR of the pseudo-random sequence and the data in the input register 11 is made into encrypted data by the exclusive OR calculation circuit 15.

In FIG. 2, the initialization of the random data generation circuit 22 is the same as in FIG.

After storing the encrypted data in the input register 21,
By driving the random data generation circuit 22 and calculating the exclusive OR of the pseudorandom sequence generated as a result and the encrypted data of the input register 21 in the exclusive OR operation circuit 25, the original input data, i.e. Plaintext appears and decryption ends.

In FIG. 3, the initial state of both shift registers a and b is set to a value by an encryption key.

*Now, let that value be f (Bo), and the first 2 of the input data
If the decimal value is A, then the binary value generated in circuit a is B, =
A, f(Bo), at this time the final value of the shift register is f
(B1).

Through such a cycle, encrypted data is created from input data.

Next, we will discuss decoding.

Considering the initial state, the initial value of the random data circuit is f(Bo) because it is set by the encryption key.

Therefore, upon input of the first bit of the encrypted data, the output of the circuit b becomes B1.f(Bo) (AI.f(Bo)).f(13o)-A, and decrypted data is obtained.

f is the feedback function of the random data generation circuit, An is the value of the nth bit of the input data, and B is the nth bit of the encrypted data.
n, and the value of the nth bit of the decoded data is Cn.

Next, we will discuss the properties of the M sequence.

This M sequence is a random number sequence with a period of 2 −1 generated by a random data generation circuit composed of an n-stage shift register and a logic feedback circuit.

Here, the period of 2n-1 means the period of the M sequence when a clock pulse is employed as the input signal sequence.

If it is created using a 32-stage shift register, it will have a long period of about 4 Gbits.

Further, the logic feedback circuit determines a pattern that is a binary code within one period, and the initial value of the shift register determines the initial phase of the pattern.

In addition to these various environments, this method uses input data as the input signal sequence, making it extremely difficult to break the code.

Furthermore, the configuration of the circuit that implements this method is also simple.

In the above explanation, bit-
This is a method of preserving the bit correspondence, that is, the one-to-one correspondence between the input signal string and the bits of the M sequence, and performing an exclusive OR operation.
The present invention is not limited to this, and there are arithmetic processing methods such as bit-block correspondence and block-block correspondence.

For bit-block correspondence, IB is used in the random data generation circuit.
IT inputs n-bit 02 from each shift register.
Extract the decimal data, that is, input data also sets n bits to 1.
In this method, a block is set, and a bit at an appropriate position within the block is used as an input signal, and an exclusive OR operation is performed with the output result M sequence of n bits/1 block.

In addition, a block-to-block correspondence method is a method in which the data is n-bit 1 block, n random data generation circuits are provided corresponding to each bit, and encrypted data is created by combining the outputs of these n and the input data. It is.

Note that there is also a method in which the initial state of the random data generation circuit is determined not directly by the cryptographic key but by −sum-converted binary data.

As explained above, the present invention obtains encrypted data using encrypted data initialized by an encryption key and input data, and outputs the random generation circuit using this encrypted data as input.
By encrypting the following input data using repeated exclusive OR operations, it is not only possible to perform encryption that is difficult to break, but also to implement it easily and inexpensively.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of encryption according to the present invention, FIG. 2 is a block diagram of an embodiment of decryption according to the present invention, and FIG. 3 is an explanatory diagram of the present invention. In FIG. 1, 11 is an input register, 12 is a random data generation circuit, 13 is a key register, 14 is a function generation circuit, and 15 is an exclusive OR operation circuit. In FIG. 2, 21 is an input register, 22 is a random data generation circuit, 23 is a key register, 24 is a function generation circuit, and 25 is an exclusive OR operation circuit. In FIG. 3, b is an explanatory diagram of encryption, and b is an explanatory diagram of decryption. In FIG. 3, Sl, S2, sn-, Sn- are shift registers.

Claims (1)

[Claims] 1. When encrypting data, the initial state is determined by the encryption key and generates pseudo-random binary data based on the input data; and its pseudo-random 2
An encryption device includes an exclusive OR circuit that creates encrypted data by performing an exclusive OR operation on binary data and the input data that generated it; A decoding device comprising a random data generation circuit that generates pseudo-random binary data using a method, and an exclusive-OR operation circuit that performs decryption by an exclusive-OR operation of encrypted data and pseudo-random binary data generated from the encrypted data. An encryption method characterized by comprising: