JPS6343754B2 - - Google Patents

Description

[Detailed Description of the Invention] (A) Technical Field of the Invention The present invention relates to a random number mixing circuit, which is used in particular with a random number generator for cryptography. , relates to a random number mixing circuit that performs transposition using random numbers discarded by compression conversion.

(B) Technical background and problems Random number generation methods include, for example, “Mathematical Science No. 203
(May, 1980), p. 77~, there are many types, but the one most often used in cryptographic machines is chained random numbers. Chained random numbers include those based on the central square method, those based on the congruential method, those based on the mixed congruential method, and those based on the Feedback Shift Register. Although these are sufficient as random numbers for general use, they are insufficient as random numbers for cryptographic machines. When looking at a random number sequence, the random number generation algorithm may be analyzed from a part of the random number sequence, so it cannot be used as is.
Therefore, by compressing or transposing the random numbers,
It is thought that this makes random number analysis difficult.

As an example of compression conversion and transposition, we will use the Data Enclosure System (DES) encryption established by the American Bureau of Standards.

FIG. 1 is a diagram for explaining an example of compression conversion, in which a 6-bit random number is compressed and converted into a 4-bit random number. Two bits (0 to 3) of the 6-bit input change the column shown in Figure 1 to the remaining 4 bits.
Select a row using bits (0 to 15) and output a 4-bit random number from 0 to 15 at the intersection.

FIG. 2 is a diagram for explaining an example of transposition.
In the case of transposition, you replace the location of a number, so to speak. For example, numbers 0 to 31 are assigned to 32 signal lines.
Then, when one of the input lines is expressed in quaternary x octal notation, it is connected to the output line shown in FIG. In this way, 32 lines are transposed to the other 32 lines.

Compression conversion and transposition as described above may seem very complicated at first glance, but if a large amount of data is handled with the logic fixed, there is a risk that it will be statistically deciphered. Also, if the encryption machine itself is stolen or
When a code is made public like DES, it only has the effect of slightly increasing the amount of work for codebreakers.

(C) Purpose and Structure of the Invention The present invention aims to solve the above-mentioned problems, and instead of using fixed conversion as in the past, it performs a conversion that changes each time it is used, making it impossible to statistically estimate the conversion algorithm. In addition, it is an object of the present invention to provide a random number mixing circuit that, when used in a cryptographic machine, for example, will not be able to be analyzed even if the cryptographic machine is stolen and the conversion algorithm is known. Therefore, the random number mixing circuit of the present invention is used together with a random number generator, and in the random number mixing circuit that performs compression conversion and/or transposition of the random numbers generated by the random number generator, the random number mixing circuit consists of a digits supplied from the random number generator. b buffer memories for storing random numbers, means for taking out c-digit data from the b buffer memories, and a buffer for outputting a part of the c-digit data and selecting a part for the next time. It is characterized in that it has a means for use in addressing the far memory. Hereinafter, embodiments will be described with reference to the drawings.

(D) Embodiment of the invention FIG. 3 shows the configuration of an embodiment of the invention, and FIG.
FIG. 3 shows a diagram for explaining the operation of the illustrated embodiment.

In the figure, B0 to B9 are buffer memories, 1
is a random number generator, 2 is an address register, 3 is a decoder, and A0 to A19 are AND circuits.

The random number mixing circuit according to the present invention is based on the following principle. The random numbers generated by the random number generator are divided into certain digits and a part of them is output. This itself can be considered to be similar to simple compression conversion. Then, using the random numbers that were not output due to compression conversion, the next division point to be used is selected. That is, processing equivalent to transposition is performed using random numbers discarded by compression conversion.

When part of a random number sequence is discarded, codebreakers have to guess the discarded random numbers and search for an algorithm to generate random numbers, which increases the amount of work they do. The more you throw away, the more work you will have to do. Next, even if the random numbers transposed by random numbers are restored assuming random numbers, there is no clue that the assumption is correct. By combining these two,
Not only can random numbers with high analysis strength be obtained, but also a random number mixing circuit with high utilization efficiency between input random numbers and output random numbers can be obtained.

In FIG. 3, a random number generator 1 generates random numbers in a chain by, for example, the mixed congruence method or the FSR method. Random numbers generated by the random number generator 1 are stored in buffer memories B0 to B9 via AND circuits A0 to A9. address·
Register 2 is a register that specifies one of buffer memories B0 to B9. address·
The address designated by the register 2 is decoded by the decoder 3 and becomes a selection signal for the output and input of the buffer memory.

For example, when address register 2 indicates the address of buffer memory B6, buffer memory B6 is selected by the output of decoder 3,
The contents of buffer memory B6 are AND circuit A16
It is taken out after passing through. At the same time, random number generator 1
The random numbers generated are set by the number of digits in the buffer memory B6 via the AND circuit A6.
A part of the data taken out from buffer memory B6 is used as an output random number, and the rest is set in address register 2 for selection of the next buffer memory B0 to B9. Random numbers are then repeatedly output in the same way.

Next, referring to FIG. 4, an example of random number mixing using the circuit shown in FIG. 3 will be described.

The random number sequence shown in FIG. 4A is generated by the random number generator 1, and is generated based on the following equation.

X _{i +1} ≡581 But “3, 6,
9, 2, 5, ......'', and regularity is found. Furthermore, the middle digit in the lower column is the middle digit in the upper column plus 3, and there is clearly a regularity in this point as well. In order to eliminate this regularity and make analysis difficult, the circuit shown in FIG. 3 is used as follows.

First, the random number generated by random number generator 1 is 2
Initialize buffer memories B0 to B9 digit by digit. As shown in Figure 4B, buffer memory B0
"72" out of "723" is stored in buffer memory B1, "37" which is the combination of the last digit of "723" and the most significant digit of "786" is stored in buffer memory B2, and "37" is stored in buffer memory B2. The values are sequentially set two digits at a time up to buffer memory B9, such as "86" out of "786". Here, assuming that address register 2 is initialized to "0", buffer memory B0 is selected first, and its data "72" is taken out via AND circuit A10. Then, for example, the left digit "7" is set as the output random number, and the right digit "2" is set in the address register 2 to be used for the next address. Note that when data is taken out from the buffer memory B0, the next random number "15" supplied from the random number generator 1 is newly set in the buffer memory B0 via the AND circuit A0.

In the next output, since the value held by address register 2 is "2", buffer memory B2
is selected, and similarly, "8" in the left digit is set as the output random number, and "6" in the right digit is set as the next address.
At this time, the next two-digit random number "04" is newly set in the buffer memory B2. Subsequently, buffer memory B6 is selected and output is repeated in the same manner. That is, as shown in FIG. 4B, the operations are performed in the following order. The output random numbers obtained in this way are as shown in FIG. 4C, and have no regularity.

In the above embodiment, it has been explained that the retrieval of random numbers from the buffer memory and the replenishment of the next random number are performed at the same time, but it is also possible to use a separate circuit for this and to also decide the order of replenishment of random numbers based on the random numbers. good. Further, the number of random number extraction digits and the number of replenishment digits may be changed. Furthermore, it is possible to arbitrarily allocate which part of the random numbers taken out from the buffer memory should be used as output random numbers, which part should be used as addresses, and which part should be discarded. The random number to be supplied is not limited to one random number generator, and it is also possible to supply outputs from two or more random number generators.

(E) Effects of the Invention As explained above, according to the present invention, a random number sequence with high analysis strength can be obtained even from a relatively simple random number sequence. Even if the mixed algorithm is known, it is nearly impossible to analyze the original random number generation algorithm from the resulting random number sequence, and this is particularly effective when applied to cryptographic machines, for example. The circuit is very simple, requires a small number of components, and can be designed economically.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining an example of compression conversion, Fig. 2 is a diagram for explaining an example of transposition, Fig. 3 is a configuration of an embodiment of the present invention, and Fig. 4 is an illustration of the implementation shown in Fig. 3. A diagram for explaining the operation of an example is shown. In the figure, 1 is a random number generator, 2 is an address register, 3 is a decoder, and B0 to B9 are buffer memories.

Claims (1)

[Claims] 1. In a random number mixing circuit that is used with a random number generator and performs compression conversion and/or transposition of random numbers generated by the random number generator, b buffers that store random numbers consisting of a digits supplied from the random number generator. memory and c from the b buffer memories.
A random number mixing circuit comprising means for taking out digit data, and means for outputting a part of the c-digit data and using the part as an address of a buffer memory to be selected next.