KR960012504B1 - Scramble & descramble apparatus for catv video signal - Google Patents

Abstract

The device consists of a scramble device and descramble device. The scramble device comprises a scramble window generator for generating a scramble window signal by a picture signal, a GMW sequence generator for supplying GMW sequence value to the encoder by using a pseudo random sequence data and phase. The descramble device is similar to the scramble device except for the picture signal in the scramble window generator.

Description

Video signal scramble and descrambler for cable broadcasting

1 is a schematic diagram of a system to scramble a conventional pay broadcast signal and send it to a subscriber.

2 is an 8-bit M-sequence circuit diagram.

3 is a schematic block diagram of a scrambler according to the present invention.

4 is a schematic block diagram of a descrambler according to the present invention.

5 is an overall multiplication circuit diagram for GMW sequence generation according to the present invention.

6 is a multiplication circuit diagram showing in detail the multiplication circuit of FIG.

7 is a block diagram of a scrambled window generator as applied to FIGS. 3 and 4;

* Explanation of symbols on main parts of the drawings

5, 5 ': Video signal source 8, 8': Synchronous separator

10: encoder 10 ': decoder

11-18: Shift register 20, 30: PN sequence generator

22, 22 ': Micom 24, 24': GMW sequence generator

26, 26 ': PN clock generator 28, 28': scrambled window generator

100, 107: short pulse generator 101-104: first to fourth counter

105, 106: SR flip-flop 108: NAND gate

109: AND gate 110: OR gate

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal scramble and descramble device for wireline broadcasting, and more particularly, to a cable television (CATV) video signal scramble and descramble device capable of improving security and adjusting a scrambled area.

In general, pay-TV is a method in which a viewer receives a broadcast service under a contract with a broadcaster when he / she wants to watch a specific broadcast. In broadcasting by a cable such as CATV, it is illegal by wire tapping. In order to prevent viewing, broadcasts are broadcast using a scramble technique that makes it difficult for an illegal urban listener to view the modified video signal by mixing interference signals with the video signal. In addition, in the radio broadcasting, since the same radio wave reaches the uncontractor, the signal is scrambled so that the uncontractor cannot receive the broadcast. In addition, the contractor may descramble the scramble signal in the reverse order of the scramble technique to watch the desired broadcast.

Conventional scramble techniques include Zenith Co., Ltd.'s Synchronization Suppression and Active Video Inversion (SSAVI), or Scientific Atlanta (SA). The conventional schemes use a pseudorandom sequence (PN sequence) to invert an image signal at an encoder. Such pseudorandom sequences include M-sequences, Kasami-sequences, and Gold-sequences, among which the features and configurations of M-sequences will be described with reference to FIG.

FIG. 1 schematically shows a system for scrambled pay broadcasting signal and sending it to a subscriber. Referring to FIG. 1, the encoder 10 receives an image signal and inverts the image based on the PN sequence value generated from the PN sequence generator 20. The subscriber receiver includes a decoder 10 'and a PN sequence generator 30. Sent to (converter) Then, the PN phase and program tag for generating the PN sequence value by the subscriber side PN sequence generator 30 are transmitted from the headend side PN sequence generator 20 to the descrambler as in-band data. Initialize the PN sequence generator 30. The receiver receiver receives the scrambled video signal and in-band data and outputs a descrambled signal through a descramble process.

The PN sequence generators 20 and 30 typically generate PN sequence signals using M-sequences, Kasami-sequences, and Gold-sequences. Here, the operation of generating M-sequences is described with reference to the M-sequence generator of FIG. Will be described.

First, the M-sequence is defined as follows.

Binary M-sequence S (t) = tr ⁿ ₄ , (α ^t ), 0 ≦ ^t ≦ N-1

However, the period N− ⁿ −1 and α is a primitive element of gallofield GV (2 ⁿ ).

In the 8-bit M-sequence circuit of FIG. 2, when the PN key value is input to the set or reset terminal, the PN sequence having a period of 2 ⁸ -1 is output while being continuously shifted by the shift registers 11-18. The PN sequence value inverts the image in the encoder 10. Although the M-sequence has many other advantages, it has been pointed out that the linear span is very small. Similarly, the Gold-sequence or Kassami-sequence is a prerequisite for correlation, but the disadvantage is that the linear span is too small. Therefore, it is pointed out that such sequences have low linear complexity and low security against the attack of the Berlekamp-Massey algorithm used to determine the whole sequence from the bush sequence. Here, the three XOR gates increase the linear span, linear complexity of the PN sequence output value, lengthen the period, and have a low autocorrelation value.

On the other hand, since the conventional Zenith SSAVI method does not use the window concept because the inversion and non-inversion information is loaded on the data line, the scramble area can be adjusted by designing it because there is no scramble window. Was not.

Therefore, in order to solve the above-mentioned disadvantages, the present invention has the same autocorrelation as the conventional M-sequence and has a very high linear complexity, GMW (a term coined by the first letters of algorithm creators Gorden, Mills, Welch). An object of the present invention is to provide a scrambled and descrambled device for comprehensive cable broadcasting, which has improved security using an algorithm.

Another object of the present invention is to provide a scrambled and descrambled device for comprehensive cable broadcasting, which can increase the viewing effect by enabling an arbitrary area on the screen to be programmed by designing a scrambled window by introducing a window concept.

Therefore, in order to achieve the above objects, the present invention provides a video signal scramble apparatus for wired broadcasting, which scrambles a video signal through an encoder and transmits it to a subscriber side under the control of a microcomputer. A scramble window is used to initialize a predetermined counter value, and to count a predetermined number of composite (CMP) synchronous signals from this video line, and to count after the predetermined number to enable a disk to generate a scrambled window signal. Generator; And receiving the scrambled window signal and receiving a predetermined pseudorandom sequence (PN) key data and PN phase under the control of the microcomputer, so that the binary GMW sequence S (t) = tr ^m ₁ ｛tr ⁿ _m (α ^t )｝ ^r (where 0 ≦ ^t ≦ N−1, 1 ≦ ^r ≦ 2 ^m −1, period N = 2 ⁿ −1, and α is a primitive element of gallofield GF (2 ⁿ ), m , n, r, t are all integers), and a GMW sequence generator for generating a predetermined GMW sequence value and supplying the encoder to the encoder is provided.

Also, in order to achieve the above objects, the present invention provides a video signal descrambling apparatus for cable broadcasting, which descrambles a scrambled video signal transmitted to a subscriber side through a decoder under control of a microcomputer, wherein the video signal descrambler is separated from the scrambled video signal. A scramble window generator for initializing a counter value using the vertical synchronous signal and counting the composite synchronous signal from the video line by a predetermined number, and disabling after counting the predetermined number to generate a scrambled window signal; And receiving the scrambled window signal and receiving predetermined PN key data under the control of the microcomputer, wherein the binary GMW sequence S (t) = tr ^m ₁ , ｛tr ⁿ _m (α ^t )｝ _r (where 0 ≦ t ≦ N-1, 1 ≦ r ≦ 2 ^m −1, α is a source of gallofield GF (2 ⁿ ), and m, n, r, and t are all integers). It provides a video signal descrambling device comprising a GMW sequence generator for generating a value and supplied to the decoder.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to an embodiment of the present invention.

The present invention increases the level of cryptographic security against various attacks by applying the GMW sequence having the same autocorrelation as the M-sequence of the same cycle and having a much higher linear complexity than the M-sequence of the same cycle. To this end, the present invention provides a scrambler and a descrambler as shown in FIGS. 3 and 4.

In FIG. 3, the sync separator 8 receives the video signal from the video signal source 5 to separate the sync signal, and the scramble window generator 28 uses the vertical sync signal separated from the video signal to adjust the counter value. It initializes and enables to count a predetermined number of CMP synchronization signals from this video line, and after counting the predetermined number, is descrambled to generate a scrambled window signal. The generated scramble window signal is transmitted to the PN clock generator 26 and the GMW sequence generator 24 to determine the PN clock generation section and the image inversion section.

The scrambled window generator 28 is configured as shown in FIG. In FIG. 7, the first to fourth counters 104 are 4-bit up-down counters (model 74193), and the counters 101-1 are short pulses of the first short pulse generator 100 using the vertical synchronization signal. Initialize 104).

The initialized first counter 101 and second counter 102 are connected by a borrow to count 28 complex synchronous signals to select line 26 of the image signal, and the second counter generated at this moment is brow. Enables the third counter 103. The third counter 103 and the fourth counter 104 are also connected by a brow to count 234 complex synchronous signals, and then SR flip-flops 105 and 106 with the short pulse of the second short pulse generator 107. The counter operation is stopped by resetting. In this way, a scrambled window can be generated.

In Fig. 7, initial values 1-4 are input to each counter 101-104, respectively.

The output of the NAND gate 108 is connected to the type force of the first counter 101. The composite synchronous signal and the output of the first SR flip-flop 105 are connected to an input of the NAND gate 108. The output of the first counter 101 is connected by the type force of the second counter 102, and the output of the second counter 102 is connected to the set terminal of the second SR flip-flop 106. The output of the AND gate 109 is connected to the type force of the third counter 103. The input of the AND gate 109 is coupled to the composite synchronous signal and the output of the second SR flip-flop 106. The output of the third counter 103 is connected by the type force of the fourth counter 104. The output of the fourth counter 104 is connected to the input of the OR gate 110. The other output of the third counter 103 is connected to the type force of the OR gate 110.

On the other hand, the binary GMW sequence applied to the GMW sequence generators 24 and 24 'of FIGS. 3 and 4 has the following formula: Binary GMW sequence S (t) = tr ^m ₁ ｛tr ⁿ _m (α ^t )｝ ^r (where 0 ≦ ^t ≦ N−1, 1 ≦ ^r ≦ 2 ^m −1, period N = 2 ⁿ −1, and α is a primitive element of gallofield GF (2 ⁿ ), m , n, r, and t are all integers), which is characterized by a very long linear span.

Each GMW sequence generator obtains a GMW sequence by solving its system of equations given the previous series of data from the minimum polynomial M ⁴ _α p (x) of α ^p in GF (2 ⁿ ).

The coefficient β _i of the minimum polynomial M ⁴ _α p (x) is expressed as a 32-fold binary vector when calculated using a combination of elements in the set. The least polynomial M ⁴ _α p (x) develops as follows:

M ⁴ _α p (x) = x ⁸ + β ₁ x ⁷ + β ₂ x ⁶ + β ₃ x ⁵ + β ₄ x ⁴ + ββ ₅ x ₅ + β ₆ x ² + β ₇ x + β ₈

=

In this case, the configuration of the entire multiplication circuit for solving the minimum polynomial is as shown in FIG.

One multiplier of the multiplication circuit shown in FIG. 5 is as shown in FIG. 6 shows a multiplication circuit of β ⁱ and the returned β ^t value. Here, the value of β ⁱ is called PN key data, and this data is stored in the ROM table. The β ^t value fed back from this multiplication circuit is determined by the initial value in the register, which is initialized by inputting to the set and reset terminals of each flip-flop as the PN phase value. Therefore, if the PN key data value and the initial phase value are the same, the same GMW sequence output value can be obtained. The coefficient β ⁱ of each term is represented by a 32-tuple binary vector, and is composed as shown in FIG. 5 when the entire multiplication circuit is constructed by one-to-one correspondence with eight 4-tuple binary vectors.

According to FIG. 6, sixteen pieces of PN key data are stored in a ROM to be calculated. That is, the PN key data values for all β _i are input into the ROM, and the addresses of the eight coefficients β _i calculated from the minimum polynomial M ⁴ _α p (x) are input to the multiplier according to the input p value. .

Referring to the operation of the GMW sequence generator configured as described above, the PN key generator software selects and stores the PN key data in the ROM.

In the scramble block, the PN phase value and the ROM table perform a continuous multiplication operation through feedback to the PN key value. This multiplication operation is traced to obtain the final GMW sequence value.

That is, the GMW sequence generator 24 receives predetermined PN key data, and the binary GMW sequence S (t) = tr ^m ₁ ｛tr ⁿ _m (α ^t )｝ ^r (where 0 ≦ ^t ≦ N-1, 1 ≦ r ≦ 2 ^m −1, period N = 2 ⁿ −1, α is a primitive element of gallofield GF (2 ⁿ ), and m, n, r, t are all integers Generates a predetermined GMW sequence value.

The GMW sequence values output from the GMW sequence generator 24 are sent to the encoder 10 to scramble and output an image signal input according to the GMW sequence values.

As described above, the present embodiment is limited to the scrambler. However, as shown in FIG. 4, the descrambler is also very similar to that of the scrambler, and thus a detailed description thereof will be omitted. However, in the descrambler, it is different that the decoder 10 'is used instead of the encoder. Other operations of the microcomputer 22 ', the scrambled video signal source 5', and the synchronous separator 8 'are the same as those shown in FIG.

As described above, when the scrambler and the descrambler of the present invention have the same autocorrelation as the M-sequence, the security against various attacks is improved by using the GMW algorithm having a large linear complexity. In addition, by adjusting the initial value of the counter of the scrambled window generator, an arbitrary area on the screen can be selected as a scrambled area, thereby increasing the viewing effect. On the other hand, the scramble technique according to the present invention can be applied to other products, in which case it is possible to reduce the system design cost than conventional methods.

Claims (2)

In an integrated cable broadcasting video signal scramble apparatus for scrambled video signals through an encoder under the control of a microcomputer and transmitting them to subscribers, the video signal scrambler is initialized by using a vertical synchronization signal separated from a video signal. A scramble window generator which is enabled to count a complex synchronous signal from a predetermined number, and is disabled after counting the predetermined number of signals to generate a scrambled window signal; And receiving the scrambled window signal, and receiving a pseudorandom sequence (PN) key data and a pseudorandom phase under the control of the microcomputer, and a binary GMW sequence S (t) = tr ^m ₁ ｛tr ⁿ _m (α ^t )｝ ^r (where 0 ≦ ^t ≦ N−1, 1 ≦ ^r ≦ 2 ^m −1, period N = 2 ⁿ −1, and α is a primitive source of gallofield GF (2 ⁿ )) element), wherein m, n, r, and t are all integers, and a GMW sequence generator for generating a predetermined GMW sequence value and supplying it to the encoder. In the integrated cable broadcasting video signal descrambling device which descrambles the scrambled video signal transmitted to the subscriber side under the control of the microcomputer, the counter value is initialized by using the vertical synchronization signal separated from the scrambled video signal, A scramble window generator that is enabled to count a predetermined number of composite synchronization signals from the video line, and is disabled after counting the predetermined number and generates a scrambled window signal; And receiving the scrambled window signal and receiving a predetermined pseudorandom key data and a pseudorandom phase under the control of the microcomputer, so that the binary GMW sequence S (t) = tr ^m ₁ ｛tr ⁿ | _m (α ^t )｝ ^r (where 0 ≦ ^t ≦ N-1, 1 ≦ ^r ≦ 2 ^m −1, period N = 2 ⁿ −1, and α is the source of gallofield GF (2 ⁿ ) , m, n, r, t are all integers; and a GMW sequence generator for generating a predetermined GMW sequence value and supplying the predetermined GMW sequence value to the decoder.