JPS60182479A - Descrambler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a descrambler that descrambles scrambled digital data.

(Prior Art and its Problems) As a method of scrambling or descrambling digital data, a method is often used in which a random number is generated and the random number is added modulo 2 to the digital data. In this case, conventional methods can be divided into two types: those in which the random number depends only on the initial value, and those in which the random number depends on the scrambled digital data. However, the method that relies only on the initial value has the disadvantage that the same random number is generated for each square after the initial direct setting, so that the random number is easily exposed to a third party. On the other hand, in the method that relies on scrambled digital data, if the original digital data has periodicity, the scrambled digital data
Periodicity also occurs in the data, and in the case of binary image transmission,
It has the disadvantage that it is possible to infer the original information even from scrambled digital data, or that if an error occurs during transmission, the error will have a long impact after decoding.

(Object of the Invention) An object of the present invention is to provide a descrambler which eliminates the above-mentioned drawbacks.

(Structure of the Invention) According to the present invention, in a descrambler that receives scrambled data and descrambles the scrambled data, pattern generating means generates a digital pattern depending on a predetermined letter key pattern. a storage means for storing a predetermined amount of data in order from the newest data among the scrambled digital data; a comparator for comparing values of the pattern generation means and the storage means; - A descrambler is obtained which is characterized by comprising data and an exclusive OR circuit which outputs digital data descrambled from the output of the comparator.

(Example) The operating principle of the present invention will be explained in detail below using diagrams showing examples.

For simplicity, it is assumed that the digital data is expressed in binary, and that the random number sequence is a sequence of one bit each.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, a shift register 103 sequentially stores binary data input from an input terminal 107, and a pattern generator 102 outputs a binary pattern depending on a key pattern from an input terminal 106. A comparator 104 is connected to the shift register 103 and the pattern generator 1.
Compares the output of 02 and outputs 0 or 1. The exclusive OR circuit 105 outputs the exclusive OR of the output of the comparator 104 and the binary data from the input terminal 107.

FIG. 2 is a block diagram showing an example of a scrambler device that generates scrambled digital data to be input to the descrambler of the device of the present invention. Figure 2 is a block diagram of Figure 1 with the left and right sides reversed, except for connections between some of the components, 202 and 102, 203 and 103.
, 204 and 104, and 205 and 105 have the same function.

In FIG. 2, a shift register 203 sequentially stores binary data outputted from an exclusive OR circuit (to be described later) bit by bit, and a pattern generator 202 stores the binary data outputted from an exclusive OR circuit (to be described later) sequentially, bit by bit.
Outputs a binary pattern depending on the key pattern from. A comparator 204 compares the outputs of the shift register 203 and the pattern generator 202 and outputs 0 or 1. The exclusive OR circuit 205 outputs the exclusive OR of the output of the comparator 204 and the binary data from the input terminal 207.

When the device of the present invention is installed on the receiving side and the device shown in Fig. 2 is installed on the transmitting side, the binary data is scrambled by the device shown in Fig. 2, and then restored to the original binary data by the device of the present invention. Show money. If the key patterns input to input terminals 106 and 206 are the same, pattern generators 102 and 202 will generate the same binary pattern.

At a certain point during operation, shift registers 103 and 2
The contents of 03 are the same binary data pulled from scratch. Also, both pattern generators 102 and 202 generate the same binary pattern. Therefore, the inputs of the same comparators 104 and 204 are the same,
The output will also be the same. The same binary number t- for binary data
Adding twice as a 2'll- method returns the original binary data, so if the device of the present invention and the device shown in Fig. 2 are installed on the receiving and transmitting sides, the binary data can be restored by the device of the present invention. .

Furthermore, even if WAb'i occurs on the shift register 103, it is stochastic that this effect will appear on the output of the comparator 104.
Normally, the expansion of a 1-bit error is suppressed to about 2 bits, so the influence of error υ propagation is small. Also, shift register 20
Since the influence of the pattern 3 above appears stochastically, the periodicity that occurs in the output due to the generation of the periodic pattern is eliminated.

The pattern generator 102 can be configured, for example, by a linear feedback shift register, and its connection state is determined by a key pattern (for linear feedback shift registers, see
Iwadare, Imai, "Coding Theory" Shokodo, published 1973, 1
(See all pages 21-135).

The initial value of the shift register can be determined in accordance with a protocol that is completely determined between transmission and reception, or it can be fixed at the beginning, or it can be changed using a synchronization code.

The comparator can be constructed by regarding each output of the shift register and a plurality of outputs of the pattern generator as multivalued signals, performing subtraction between the two signals, and outputting the sign thereof.

(Effects of the Invention) As explained above in detail, by using the present invention, error propagation can be reduced, and periodic digital data can be decoded by a third party because the periodicity is eliminated. It is possible to descramble digital data that has been scrambled in a difficult manner, and is extremely effective when used in a communication system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a diagram showing an example of a device for generating scrambled digital data input to the device of the present invention. In the figure, 102, 202 are pattern generators, 103
．． 203 is a shift register, 104.20.1 is a comparator, and 105.205 is an exclusive OR circuit. O 1 Figure O 2 Figure

Claims (1)

[Claims] In a descrambler that receives scrambled data and descrambles the scrambled data,
pattern generating means for generating a digital pattern in dependence on a predetermined key pattern; storage means for storing a predetermined amount of data in order from the newest data among the scrambled digital data; a comparator for comparing the values of the pattern generation means and the storage means; and a digital signal descrambled from the scrambled data and the output of the comparator.
Descrambler-0 characterized by consisting of an exclusive OR circuit that outputs data