JP2755453B2 - Data scrambler - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data scrambler for securing data confidentiality.

2. Description of the Related Art As one of conventional general methods, there is a method in which a pseudo-random code is exclusive-ORed with information data to secure confidentiality of the information data. Since the pseudo-random code is uniquely determined according to the generator polynomial, only those who can know the generator polynomial can restore the data.

FIG. 3 shows a block diagram of a conventional data scrambler based on the above method. 3 is a scramble key generator,
Reference numeral 4 denotes an exclusive-OR calculator (hereinafter referred to as EX-OR), and reference numeral 5 denotes a pseudo-random code generator that generates a pseudo-random code based on an output signal of the scramble key generator 3 and controls the EX-OR 4.

FIG. 4 shows an example of the configuration of the pseudo-random signal generator 5 using a ten-stage shift register. Where 51 is EX-O
R and 52 are D-FFs with an initial value set. The generator polynomial is
Determined by the position of the return tap (EX-OR51 position)
In the case of the figure, G (x) = X ¹⁰ + X ³ +1. With this configuration, the period of the pseudo-random code sequence to be output is 2 ¹⁰ −1 = 1023. That is, 1023
The same code sequence is repeatedly generated in bit units.

Hereinafter, a conventional data scrambler will be described with reference to FIG. The scramble key generator 3 gives an initial value of the shift register of the pseudo random code generator 5.
The output of the pseudo-random code generator 5 starts from this initial value and is specified by the generator polynomial G (X).
It becomes a pseudo-random code sequence having a bit period. The code sequence and the input information data sequence are exclusive-ORed by EX-OR4 and scrambled to obtain the EX-O
The scrambled information data is obtained at the output of R4.

If the scramble key and the time to give the scramble key are given to the authorized receiver of the data in advance, the same pseudo-random code sequence as that generated by the pseudo-random code generator 5 can be generated, and the data can be restored. Becomes

Problems to be Solved by the Invention However, the above configuration has the following problems in securing data confidentiality.

The period of the pseudo random code sequence is determined by the number of stages of the shift register shown in FIG. Also, by observing the received data, there is a high possibility that a generating polynomial of a pseudo-random code sequence is determined from a periodically generated data sequence. Even if the initial value of the shift register is periodically updated, the start position of the code sequence changes but the content of the code sequence does not change, so that the confidentiality of the information data is not significantly improved. If the number of stages of the pseudo-random code generator is relatively small, it is easy to find a generator polynomial for pseudo-random code generation, and the confidentiality of data is reduced. In order to ensure data confidentiality, it is necessary to increase the number of register stages and lengthen the period of the pseudo-random code. For this reason, the conventional technique has a problem that the scale of the realized circuit is enormous.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a data scrambler having a small circuit size of a pseudo-random code generator and ensuring data confidentiality.

Means for Solving the Problems In order to solve the above problems, a data scrambling device of the present invention includes a generator polynomial variable pseudo-random code generator having a plurality of generator polynomials, and a generator polynomial of the pseudo random code generator. Generator polynomial switching order control means for controlling the switching order, scramble key generation means for outputting a scramble key for controlling the generation polynomial switching order control means, an input information data sequence and an output code sequence of the pseudo random code generation means. Exclusive OR operation means for inputting the scramble key, and the order is changed at a time interval shorter than the update cycle of the scramble key, and the order is changed according to the switching order obtained as the output of the generator polynomial switching order control means. Switching the generator polynomial of the pseudo-random code generator And a scrambled information data sequence is obtained at the output of the exclusive OR operation means.

According to the above-described means, even if the pseudo-random code is generated by a shift register having a small number of stages, the secrecy of the scrambled data is ensured. This is because, since the generator polynomial of the pseudo-random code generator changes at a shorter time interval than the scramble key update interval, it is difficult to identify the code generation generator polynomial even when observing the scrambled data, which is equivalent. This is the same as scrambling with a pseudo-random code having a long cycle, and data confidentiality can be secured.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a data scrambler according to one embodiment of the present invention. In FIG. 1, 1 is a pseudo-random code generator capable of generating polynomial switching, 2 is a generator polynomial switching order controller, 3 is a scramble key generator, 4
Is an exclusive-OR operator (EX-OR), and the generator polynomial switching order controller 2 determines the switching order of the switchable pseudo-random code generator 1 in accordance with the output of the scramble key generator 3, The code generator 1 generates a pseudo-random code of a generator polynomial according to this order,
Control EX-OR4.

FIG. 2 shows a configuration example of the pseudo-random code generator 1. Pseudo-random code generator 1 is AND gate 101, EX-OR1
02, composed of 10-stage shift register consisting of D-FF103, and EX-OR102 which is a switch of feedback tap,
The generator polynomial can be switched. The generator polynomial is determined by the position of the feedback tap, and a plurality of generator polynomials are provided. Of these generator polynomials, some of which have the maximum period (in the case of 10 stages; 1023 bits) are selected and used as switching generator polynomials. Now, consider a case in which eight generator polynomials are selected from G1 (X) to G8 (X). The switching order controller 2 outputs a tap position switching signal at specific short time intervals according to the scramble key. Thereby, a pseudo-random code sequence having a different generating polynomial is output to the output of the pseudo-random code generator 1 at short time intervals. The pseudo-random code sequence is EX-ORed with the input information data sequence, and the input data is scrambled.

Since the switching order controller 2 determines the order of the generator polynomials to be switched according to the scramble key, a signal for selecting G1 (X) to G8 (X) at each generator polynomial switching time interval with the scramble key update time at the top. Are sequentially output. This output sequence is prepared independently for the key of the scramble key generator 3. The switching order controller 2 stores, for example, a sequence having a longer cycle than the switching interval in a ROM.
A specific bit is extracted from the M sequence at each switching time and a code is extracted from G1 (X) to G8 at each switching time.
This can be realized by a method of performing code conversion into a feedback tap position switching signal for selecting the generator polynomial of (X).

By the above method, the pseudo-random code generated by the 10-stage shift register is not a sequence having a fixed period of 2 ¹⁰ -1 but a code sequence in which the generating polynomial is sequentially switched at short time intervals. Further, when the scramble key is updated, the generation order of the generator polynomial changes, and the secrecy of data increases. As compared with the case of using a pseudo-random code sequence generated by a specific generator polynomial in this way, it becomes more difficult to identify the generator polynomial used even when observing the scrambled information data, and an equivalently long period is used. An effect of scrambling using the pseudo random code is obtained.

As described above, according to the present invention, according to the present invention, the generator polynomial of the pseudo-random code generating means is switched at a shorter time interval than the update cycle of the scramble key according to the switching order of the generator polynomial determined by the scramble key, and further scrambled. By updating the key, scramble of highly confidential data can be realized with a smaller number of stages.

[Brief description of the drawings]

FIG. 1 is a block diagram of a data scrambler according to an embodiment of the present invention, FIG. 2 is a block diagram showing an example of a pseudo-random code generator capable of switching a generator polynomial in the data scrambler, and FIG. FIG. 4 is a block diagram of a data scrambler, and FIG. 4 is a block diagram of a general pseudo-random code generator in a conventional data scrambler. 1 ... generator polynomial switching variable pseudo-random code generator, 2 ... generator polynomial switching order controller, 3 ... scramble key generator, 4 ... exclusive OR operator, 101 ...
… AND gate, 102… Exclusive OR operator, 103… D-FF with initial value set.

Continuation of the front page (72) Inventor Shunichi Nezu 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-141231 (JP, A) Third Edition (H1-5-20) IEICE P. 25-30

Claims (1)

(57) [Claims] A generator polynomial having a plurality of generator polynomials, a variable pseudo-random code generator, a generator polynomial switching order controller for controlling an order of switching the generator polynomials of the pseudo random code generator, and a generator polynomial switching order. A scramble key generation means for outputting a scramble key for controlling the control means; and an exclusive OR operation means for inputting an input information data sequence and an output code sequence of the pseudo random code generation means, wherein the control is performed by the scramble key. Wherein the generator polynomial of the pseudo-random code generator is switched in accordance with a switching order obtained as an output of the generator polynomial switching order controller, the order being changed at a time interval shorter than the scramble key update cycle. Scrambled at the output of the logical OR operation means Configuration data scrambling apparatus to obtain over data sequence.