JPH0723367A - Method for scrambling and its device - Google Patents

Abstract

PURPOSE:To obtain a scrambling method capable of attaining scramble with high degree of agitation without generating deterioration in a reproduced picture in respect to a scrambling method to be used for a digital communication system following compression processing. CONSTITUTION:A dividing device 11 divides the video data of an inputted frame into scramble blocks each of which includes at least one minimum data unit for compression processing to be executed by a communication system. An inverting device 12 attains scramble by inverting all picture element signals in a scramble block specified by a random number based upon the intermediate value of a dynamic range. Since the correlation of data in the processing unit for executing compression processing by scramble is not destructed, compression efficiency is not changed and a reproduced picture is not deteriorated.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a digital video signal,
The present invention relates to a scramble method and a scramble apparatus used for secretly communicating in a communication system in which data is compressed by a compression process and then transmitted / received or recorded / reproduced by a wired or wireless or storage medium.

[0002]

2. Description of the Related Art As a conventional scramble system for encrypting and communicating a video signal, for example, it is shown in Chapter 8 of "Cryptography and Information Security" (published by Shokodo Publishing; Shigeo Tsujii et al.). There are various types of conventional scramble systems. For example, the best known methods include an intra-scanning line signal switching system, a scanning line transition system, and a polarity reversal system, and these systems are used alone or in combination.

FIG. 5 specifically shows a conventional intra-scanning line signal switching system in the scrambling system. It shows the processing when one frame in a video signal composed of a plurality of frames is processed. It is a figure which shows an outline. 5A shows the video signal before scramble, and FIG. 5B shows the video signal after scramble.

An outline of the scramble process will be described below with reference to FIG. First, a random number is given to the scanning line a in FIG. 5A, and the scanning line a is, as shown in FIG. 5A, a set A of two pixel signals at a position indicated by the random number.
And B. Next, A and B are left and right interchanged, and the structure shown in the scanning line a in FIG. 5B is obtained.

Similarly, the scanning line b in FIG. 5 (a) is also divided into two pixel signal sets C and D by a given random number, and C and D are transposed to the left and right to scan in FIG. 5 (b). Line b
The configuration is as shown in. Here, in FIG. 5, only the processing for the scanning line a and the scanning line b is shown, but the same processing is actually performed for all the scanning lines.

FIG. 6 specifically shows the scanning line transition method in the scramble method of the conventional example, and shows an outline of processing when one frame in a video signal composed of a plurality of frames is processed. FIG. Figure 6
6A shows a video signal before scramble, and FIG. 6B shows a video signal after scramble. The outline of the scramble process will be described below with reference to FIG. First, a random number is instructed to replace the data at the position of the scanning line a with the position of the scanning line d and the data at the position of the scanning line b with the position of the scanning line c.

Next, assuming that the data of the scanning line a is A and the data of the scanning line b is B, the scrambling process shown in FIG.
As shown in (b), the data of the scanning line c becomes B and the data of the scanning line d becomes A. Here, in FIG. 6, only the process for the data of the scanning line a and the scanning line b is shown, but the same process is actually performed for all the scanning lines.

The polarity inversion method is a method of inverting a signal in the baseband state around a certain reference level, and inversion processing is performed randomly in line units or frame units by random number instructions.

A conventional random number (hereinafter referred to as PN) addition method has been used as an encryption method for encryption and communication of digital signals. Encryption of random number addition of digital audio signals is introduced, for example, in the above-mentioned “Cryptography and Information Security” p.178 to p.179. The random number addition method is a method in which the result of exclusive OR of a random number and a digital signal for each bit is output after encryption.

An example of a digital communication system for compressing the data amount of a digital video signal by a compression process for reducing the correlation between neighboring pixels and transmitting the data through a transmission line is disclosed in Japanese Patent Application No. 5-37691 (Applicant: Matsushita). Denki Sangyo Co., Ltd., Heisei 5
(February 17, 1998) and the special feature "High efficiency coding of images are unified" (p.115-p.142) of Nikkei Electronics 511 (October 15, 1990). There is.

FIG. 7 shows the configuration of a compression device in this conventional digital communication system. In FIG. 7, 71
Is a dividing device, 72 is a converting device, and 73 is a bit allocating device. The operation of the compression device shown in FIG. 7 will be described below.

First, the dividing device 71 converts the input video data into 8
The data is divided into DCT blocks composed of pixels × 8 scanning lines and output. Next, the conversion device 72 converts the DCT block output from the division device 71 into a frequency component by performing data conversion by DCT (discrete cosine transform), and outputs it as conversion data. Next, the bit allocation device 73 allocates an appropriate bit to each frequency component of the converted data output from the conversion device 72, and outputs it as compressed data.
At this time, when bits are allocated in the bit allocation device 73, compression is realized by reducing the allocation of bits to AC components.

The principle of compression processing will be described below. The compression process realizes the reduction of the amount of transmission data by utilizing the high correlation between neighboring pixel signals in the video data. Here, the property that the correlation between pixel signals is high in each DCT block and most of them become a DC component and a low frequency component when converted into a frequency component is used. That is, after conversion into frequency components, the DC component of the data of each frequency component gives many bits,
The AC component realizes compression by reducing the bits given to the higher frequency components.

When a plurality of video signals are compressed by the same compression processing, the degree to which they can be compressed depends on the nature of the video signals. That is, the DCT having a high correlation between pixel signals
As for the block, the high frequency component of the converted data becomes small, and as a result of the compression processing, the data can be represented by a small number of bits. The fact that the data can be represented with a small number of bits by the compression process is called high compression efficiency.

On the contrary, for a DCT block in which the correlation between pixel signals is low, the high frequency component of the converted data becomes large, and as a result of the compression process, many bits are required to represent the data. The compression process requires a large number of bits to represent the data, which means that the compression efficiency is low.

Considering the case where the compressed data is transmitted through a transmission line having a fixed capacity, a DCT having a high compression efficiency.
Since data can be represented by a small number of bits in a block, the transmission path can be transmitted without discarding bits or by discarding only a few bits. Therefore, the difference between the image after compression / expansion and the original image is small. However, since a DCT block with low compression efficiency requires many bits to represent data, a DCT block with high compression efficiency is required to transmit on a transmission line having a determined capacity.
Bits representing more data than T blocks need to be truncated. Therefore, the image after being compressed and expanded is deteriorated as compared with the original image.

[0017]

However, in the conventional scanning line switching system, scanning line transition system, scrambling system by scanning line unit polarity reversal system, and in the conventional encryption system, the digital data with compression processing is used. When applied to a communication system, if scrambling is performed without taking the compression processing into consideration, there is a problem that a reproduced image is deteriorated by the scrambling processing and the descramble processing. The reason is shown below.

In the conventional scramble method, when scrambling is performed on the video signal before being transmitted in the digital communication system for performing the compression processing by DCT shown in the conventional example, in the DCT block in the scrambled video signal. The correlation at is lower than that of the video signal before scrambling. For example, considering the case where scrambling is performed by the scanning line signal switching method of the conventional example, in the scanning line signal switching method, since the cutting point is selected by a random number for each scanning line, the correlation between scanning lines is destroyed by scrambling. Is
The vertical correlation within each DCT block is broken. Further, in the DCT block including the cut point, the correlation in the horizontal direction is also broken.

As described above, in the DCT block in which the correlation between the pixel signals is destroyed, many bits are required to represent the data after the compression process, so the data is truncated and the data after the compression expansion is compressed. The reproduced image deteriorates compared to the original image. Therefore, in the scramble method of the conventional example, when the video signal before being transmitted in the digital communication system that performs the DCT compression processing shown in the conventional example is scrambled, the reproduced image is compared with the original image. to degrade.

Further, the above-mentioned conventional encryption method completely digitizes digital data. Therefore, in the conventional encryption method, when the video signal before being transmitted in the digital communication system which performs the compression process by the DCT shown in the conventional example is encrypted, the DCT in the encrypted video signal Since the correlation within the block is lower than that of the video signal before encryption, the compression efficiency of the compression process decreases,
The reproduced image deteriorates.

Further, the scrambling method based on the polarity reversal method on a frame-by-frame basis has a problem that sufficient safety cannot be obtained. The reason for this is shown below.

In the polarity reversal method on a frame-by-frame basis, since inversion processing is carried out randomly on a frame-by-frame basis according to an instruction of a random number, each frame requires only a 1-bit random number which is inverted or not inverted. Therefore, the image before scramble can be easily estimated, and the safety is not sufficient.

In view of the above points, the present invention provides a scramble method and a scramble device which can realize a scramble that does not cause deterioration in a reproduced image and can obtain sufficient safety when used in a digital communication system involving compression processing. The purpose is to do.

[0024]

According to the present invention, one frame of digital video data is processed, and the one frame of digital video data is compressed by a minimum data unit.
Divide into scramble blocks containing one or more, divide the scramble block into an inversion scramble block and a non-inversion scramble block by the instruction of a random number, and center all the pixel signal values in the inversion scramble block around the intermediate value of the dynamic range Invert the level.

[0025]

According to the present invention, due to the above-mentioned structure, the inversion scramble block is subjected to the inversion process by scrambling, and has a property different from that of the original image.
Inverted scrambled blocks and non-inverted scrambled blocks are randomly mixed in one frame of digital image data after scrambled, so that the image becomes very difficult to view as a whole.

Further, since the inversion scramble block and the non-inversion scramble block are selected by random numbers, it becomes difficult for anyone who does not know the random numbers to decrypt them.
Sufficient safety can be obtained.

Further, since all pixel signals in the scrambled block which has been inverted are inverted, the difference between the pixel signals is only reversed in sign. Therefore, the correlation between the pixel signals in the minimum data unit of each compression process included in the scramble block does not change before and after scramble. This makes it possible to realize scrambling in which the reproduced image does not deteriorate.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a scrambler for realizing a scramble method according to a first embodiment of the present invention.

In FIG. 1, reference numeral 11 is a division device for dividing one frame of digital video data as input data and dividing the input data into scramble blocks containing at least one minimum data unit for compression processing, and outputting the divided scramble blocks. Device 1
The scramble block and the random number output from 1 are input, and the result of level inversion of the values of all the pixel signals in the scramble block indicated by the random number around the intermediate value of the dynamic range is output, An inversion device that directly outputs scrambled blocks that are not instructed, 13 inputs the scrambled blocks output from the inversion device 12, rearranges the scrambled blocks by means reverse to the processing in the dividing device 11, creates digital video data, and outputs it. It is a synthesizer that outputs as data.

The operation of the scrambler according to this embodiment having the above-mentioned structure will be described below. First,
The dividing device 11 inputs one frame of digital video data as input data, divides the input data that has been input,
Output as a scramble block. At this time, the dividing device 11 uses the DCT block, which is the minimum unit of the compression processing in the compression processing shown in FIG. 6, as the scramble block for the input data.

Next, the reversing device 12 inputs a scramble block and a random number corresponding to the scramble block, determines whether to invert or not to invert according to the instruction of the random number, and when it does not invert, inputs it. When the scramble block is output as it is and inverted, all the pixel signals in the scramble block are inverted, and then the scramble block is output. Here, an example of pixel signal inversion processing is shown in FIG.

FIG. 2A shows a dynamic range of 100.
011 indicates the inversion of the pixel signal represented by a 3-bit signed 2's complement integer. Also,
FIG. 2B shows a dynamic range of 000 to 111.
2 shows the inversion of the pixel signal represented by a 3-bit unsigned integer. As described above, the inversion process is a process of selecting an intermediate value between the maximum level and the minimum level of the pixel signal as the reference value and folding each pixel level around the reference value.

Next, the synthesizing device 13 inputs the scramble block output from the inverting device 12, and the dividing device 1
The scramble blocks are rearranged by the means reverse to the processing in 1 to make digital video data and output as output data.

The descrambling device according to the first embodiment has the same structure as the scrambling device according to the first embodiment shown in FIG. 1, and comprises a dividing device 11, an inverting device 12 and a synthesizing device 13.

The operation of the descrambling device in the first embodiment configured as described above will be described. Divider 1
1 and the synthesizing device 13, the dividing device 11 and the synthesizing device 13 in the scrambling device of the first embodiment.
Since the operation is exactly the same as the above, only the operation of the reversing device 12 is shown below.

The inversion device 12 inputs the scramble block and uses the same random number as that used in the inversion device 12 of the scramble device in the first embodiment for each scramble block in the first embodiment. The same process as the process in the reversing device 12 of the scrambler in FIG.

As described above, according to the present embodiment, with respect to the scramble block designated by the random number, the scramble is realized by inverting all the pixel signals in the scramble block by the above-mentioned configuration. As a result, scrambled blocks that have been inverted and scrambled blocks that have not been inverted are mixed in the same frame, so that the video as a whole is very difficult to view and worth listening. Further, the scrambled block to be inverted is selected by a random number, and the scrambled block that has been inverted and the scrambled block that has not been inverted are mixed in one frame. For those who do not know, it is difficult to decipher and sufficient security can be obtained.

Further, in the scrambled block which has been inverted, all the pixel signals therein are inverted, and therefore the difference value between the pixel signals in the scrambled block which has been inverted is simply reversed. is there. Therefore,
The correlation between the pixel signals in the scramble block does not change before and after scrambling. That is, DC
When data such as T is converted, the AC component of the converted data does not change at all. Therefore, since the compression efficiency of the video data after being scrambled by the scrambler of the present embodiment is not reduced, the video data after being scrambled is compressed.
The reproduced image when compressed and decompressed and descrambled does not deteriorate as compared to when the image is not scrambled.

Incidentally, the reversing device 12 in the first embodiment.
Can be realized by the reversing device having the configuration shown in FIG.
In FIG. 4, 41 is an exclusive OR device, and 42 is a switch device.

The operation of the reversing device shown in FIG. 4 will be described below. The switch device 42 determines whether or not to perform the inversion by controlling the random number, outputs 0 as the control signal when the inversion is not performed, and outputs 1 as the control signal when the inversion is not performed. . The exclusive OR device 41 inputs the control signal output from the scramble block and the switch 42, and outputs the result of the exclusive OR of the control signal to all the bits of the scramble block as a scrambled scramble block.

As described above, according to the inverting device shown in FIG. 4, the inverting process in the inverting device of the scrambler of the first embodiment shown in FIG. 2 can be realized.

In the scrambler according to the first embodiment, the pixel signal which is all the numerical values that can express the dynamic range is scrambled. However, the dynamic range of the pixel signal to be processed is Even if it is smaller than the dynamic range shown in the first embodiment, if the pixel signal of the divided block input by the inverting device 12 is inverted at the intermediate value of the dynamic range, it is similarly scrambled. Things can be done with the same effect.

In the scrambler of the first embodiment, the case where the pixel signal represented by 3 bits is scrambled is shown, but the case where the pixel signal represented by 4 bits is scrambled is also shown. This can be realized by the similar inversion processing as shown in 3, and the same effect can be obtained. Here, FIG. 3A shows a state of inversion of a pixel signal represented by a 4-bit signed 2's complement integer with a dynamic range of 1000 to 0111. In addition, FIG. 3B shows that the dynamic range is 000.
0 to 1111 shows the inversion of the pixel signal represented by a 4-bit unsigned integer.

In the scrambler of the first embodiment, the case where the pixel signal represented by 3 bits is scrambled is shown, but an arbitrary positive integer n
Even when scrambling a pixel signal represented by bits, the same effect can be obtained by the same inversion processing.

Although the DCT block is a scramble block in the scrambler of the first embodiment, the same effect can be obtained even if a plurality of DCT blocks are combined into a scramble block.

In the scramble apparatus of the first embodiment, the DCT block is a scramble block in order to adapt to the conventional digital communication system for performing the compression processing shown in FIG. In the case of applying to a digital communication system that performs compression processing, if the configuration is such that one or more minimum data units of the compression processing performed in the applied digital communication system are combined into a scramble block, the same result is obtained. The effect is obtained.

The dividing device 11 in the scrambler of the first embodiment performs a process of dividing the input video signal into DCT blocks. Further, since the same processing is performed in the dividing device 71 in the communication system of the conventional example shown in FIG. 7, the dividing device 11 in the first embodiment is shared with the dividing device 71 in the communication system of the conventional example. With such a configuration, the dividing device 11 in the scrambler of the first embodiment is not needed, and the same effect can be obtained.

Although the inversion device 12 in the scrambler of the first embodiment performs the inversion process on the scramble block indicated by the random number, it performs the inversion process on the scramble block indicated by the fixed sequence. With such a configuration, although the security is slightly inferior, when used in a digital communication system involving compression processing, it is possible to easily realize a scramble system in which a reproduced image does not deteriorate. Furthermore, in this case, it is not necessary to send a random number to the descrambler.

The input data in the scrambler of the first embodiment is supposed to be a digital video signal of one frame, but when digital video signals of a plurality of frames are to be processed, one frame of digital video signal is processed. It goes without saying that if the digital video signal is repeatedly processed, it can be similarly scrambled.

The input data in the scrambler of the first embodiment is assumed to be one frame of digital video signal, but when applied to a digital communication system in which compression processing is performed for each field. The same effect can be obtained by processing a 1-field digital video signal as input data.

[0051]

As described above, according to the present invention,
When used in a digital communication system with compression processing,
It is possible to realize a scramble method that does not cause deterioration in a reproduced image and can obtain sufficient safety, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a scramble device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an outline of an inversion process of a scrambler in the first embodiment.

FIG. 3 is a diagram showing an outline of an inversion process of a scrambler in the first embodiment.

FIG. 4 is a block diagram of an inversion device of the scrambler in the first embodiment of the present invention.

FIG. 5 is a diagram showing an outline of processing by a conventional scanning line signal switching method.

FIG. 6 is a diagram showing an outline of processing by a conventional scanning line replacement method.

FIG. 7 is a block diagram showing a configuration of a compression processing part in a conventional digital communication system.

[Explanation of symbols]

 11 splitting device 12 inverting device 13 combining device 41 exclusive OR device 42 switch device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location H04L 9/10 9/12 (72) Inventor Hironori Murakami 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Within the corporation

Claims (2)

[Claims] 1. A digital video data of one frame is processed, and the digital video data of one frame is divided into scramble blocks including one or more minimum data units of compression processing, and the scramble block is specified by a random number. Is divided into an inversion scramble block and a non-inversion scramble block, and the values of all pixel signals in the inversion scramble block are level-inverted around an intermediate value of the dynamic range. 2. A dividing device for dividing one frame of digital video data as input data and dividing the input data into scramble blocks containing at least one minimum data unit for compression processing, and outputting the divided data. The scramble block which is not designated by the random number, which is the input of the scramble block and the random number, outputs the result of level inversion of the values of all the pixel signals in the scramble block designated by the random number around the intermediate value of the dynamic range. Is a scrambler that consists of a signal inverting device that outputs as is.