JPH07111645A - Scramble device and descramble device - Google Patents

Abstract

PURPOSE:To obtain a scramble device and a descramble device which are capable of performing the scramble processing completed by a packet and obtaining sufficient secrecy of video, in a digital video communication system transmitting a video signal by performing the compression processing by a conversion encoding to the video signal and making the signal in a packet form. CONSTITUTION:A data location 34 to be ciphered as the location of data to be ciphered by a block ciphering system in a ciphering device is surely incorporated with a DC component 32 and a data location 35 which is not to be ciphered is composed of only an AC component 33. Thus, because the DC component affecting largely on a reproduced image is surely ciphered, the reproduced image has sufficient irregularities, and sufficient secrecy is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scramble used for secret communication in a communication system in which a digital video signal or digital data is packetized after being compressed and is transmitted / received or recorded / reproduced by a wired or wireless or storage medium. The present invention relates to a device and its descrambling device.

[0002]

2. Description of the Related Art First, a conventional encryption device for encrypting digital data will be described. As a conventional encryption device,
Those using a block encryption method such as DES and FEAL are well known. These block encryption methods are disclosed in JP-B-59-36463 and JP-A-63-20.
No. 4289 is disclosed. In the encryption processing by these block encryption methods, a certain size of data is processed as one unit. Here, the unit in which this processing is performed is defined as an encrypted block.

As an example, an operation of an encryption device for encrypting data by a block encryption method using an encryption block having a size of 64 bits will be shown. 64 in the encryption process
When bit data is input, 64-bit data that is the result of encryption processing is output. In the decryption process, 64-bit data that is the result of the encryption process is input, and 64-bit data that is the result of the decryption process that is the inverse conversion of the encryption process is output.

Next, a conventional digital video communication system will be shown. In a conventional digital video communication system, a compression-coded digital video signal may be transmitted in packet units. An example of such a digital communication system is disclosed in Japanese Patent Laid-Open No. 5-49002.
The processing in the conventional digital video communication system will be described below. As for the order of description, the compression encoding process will be described first, and then an example of the packet structure will be described.

First, the compression coding will be described. The compression encoding is a process of reducing the amount of transmission by transmitting a digital video signal so that the correlation in the signal is reduced. Typical compression encodings include transform encoding represented by a method using DCT (discrete cosine transform) and variable length encoding represented by Huffman encoding. In transform coding, an image block consisting of multiple pixels is divided into frequency components, and many bits are given to DC components and low-frequency components, but compression is realized by reducing the bits given to high-frequency components of AC components. . In the variable length coding, compression is realized by assigning a small bit code to data having a high appearance probability and assigning a large bit code to data having a low appearance probability.

Next, an example of the structure of a packet packetized after compression coding in a conventional digital video communication system will be described with reference to the drawings. Here, FIG. 8 shows the case where the transform coding is used as the compression coding, and FIG. 9 shows the case where the variable length coding is used as the compression coding.

FIG. 8 shows an example of the structure of a packet that is packetized after transform coding. 81 indicates control data, 82 indicates a DC component, and 83 indicates an AC component. The operation of generating the packet of FIG. 8 will be described below.

First, an image block consisting of a plurality of pixels is divided into frequency components by transform coding, and each component is quantized into a code to form a DC component 82 and an AC component 83. Next, these components are packetized together with the control data 81 used for controlling communication, and the packet shown in FIG. 8 is generated.

FIG. 9 shows an example of the structure of a packet that is packetized after variable length coding, in which 91 is control data, 92 is fixed length data, and 93 is variable length data.
The operation of generating the packet shown in FIG. 9 will be described below.

First, the data to be processed is divided into the fixed length data 92 and the data of the variable length encoded portion, and the data of the variable length encoded portion is compression encoded by the variable length encoding. Then, variable length data 91 is created. Next, fixed length data 92 and variable length data 93
Are packetized together with control data 91 used for controlling communication, and the packet shown in FIG. 9 is generated.
Here, the fixed length data 91 may not be present depending on the system.

Finally, a conventional scrambler for encrypting data that is packetized and transmitted after compression encoding in a conventional digital video communication system by using a conventional encryption device will be described. Here, in the packet data of the digital video communication system of the conventional example, the data to be encrypted is excluded except for the data portion for which it is prohibited to encrypt the control data used for communication control. The data part is defined as the encryption target data. The operation of the conventional scrambler will be described below.

In the conventional scrambler, processing is performed between packets in order to prevent an error from extending between different packets and to match processing in packet units performed in the conventional digital video communication system. The scramble process is performed so that the packet is completed within the packet. That is, a conventional scramble device inputs a packet transmitted by a conventional digital video transmission system, encrypts the data to be encrypted of the input packet by a conventional encryption device by a block encryption method, and outputs the result. It is combined with unencrypted data and output as a scrambled packet.

FIGS. 10 and 11 show the positions of encryption when scrambling the packets transmitted in the conventional digital video communication system shown in FIGS. 8 and 9 in the conventional scrambling device. And 1
01 indicates a data position where encryption is not performed, and 102 indicates an encrypted block. Here, one block of the encryption block 102 corresponds to an encryption block. As shown in the figure, the size of the data to be encrypted is an integral multiple of the size of the encrypted block.

[0014]

As described above, in the conventional scrambler, the size of the data to be encrypted is an integral multiple of the size of the encryption block of the encryption device to be used. However, the size of the data to be encrypted in the digital video communication system and the size of the encryption block in the encryption device are individually determined so as to be optimal for realizing the required functions, performances, and costs. If it is designed so that the size of the data to be encrypted is an integral multiple of the size of the encrypted block, the function, performance, cost, etc. may be impaired.

Further, in one video communication system,
If the size of the data to be encrypted is not constant and the data to be encrypted of different sizes are mixed, the size of the data to be encrypted and an integer multiple of the size of the encryption block of the encryption device used Matching can be achieved in a specific packet but not necessarily in all packets.

For these reasons, the size of the data to be encrypted may not be an integral multiple of the size of the encrypted block. In this case, if the data to be encrypted is simply divided into encryption blocks and scrambled by the same encryption device, the part of the data to be encrypted that cannot be encrypted will remain, and the image will be recorded in the part that cannot be encrypted. If the important data characterizing the above is included, the content can be specified to some extent from the scrambled video, and sufficient confidentiality cannot be obtained.

Therefore, in the present invention, in a digital video communication system in which a digital video signal is compressed and packetized for transmission, an encryption device for encrypting the scramble processing completed in packets by a block encryption method. When using the, it is possible to obtain sufficient video confidentiality even if the size of the data to be encrypted in the packet is not an integral multiple of the size of the encryption block of the encryption device. An object is to provide a scrambler and a descrambler.

[0018]

According to a first aspect of the present invention, a digital video signal divided into packets after compression processing based on frequency conversion is performed is to be processed, and the packets are used as input data. The scrambler is characterized in that the DC component in the packet is encrypted by a block encryption method.

According to a second aspect of the present invention, digital data packetized after being compressed by a variable length code is processed, and at least the first few bits of the variable length code are encrypted by a block encryption method. The scrambler is characterized by the following.

A third aspect of the present invention targets a packet after being scrambled by the scrambler according to the first or second aspect of the invention, and performs block encryption on a portion encrypted by the scrambler. It is a descrambling device characterized by performing decoding by a method.

[0021]

According to the first aspect of the present invention, the DC component having a great influence on the reproduced image in the video signal divided into the frequency components is always subjected to the encryption processing and the random number generation.
Even if the AC component is correct, the reproduced image will be a sufficiently disordered image. Therefore, it is difficult to infer the original image from the scrambled image, and it is possible to obtain sufficient confidentiality.

According to the second aspect of the invention, with the above-mentioned configuration, the encryption process is always performed at the head of the variable length code. If even one bit error is present in the variable-length coded data, in the worst case, the error is propagated until it is refreshed.
Even if there is an unencrypted part in the latter half of the variable length code, there is a high possibility that that part will be determined as an erroneous code. As a result, the effect more than the randomization by the encryption process is actually obtained, and higher confidentiality can be obtained.

According to the third aspect of the invention, with the above configuration, the packet after being scrambled by the scrambler of the first aspect or the second aspect of the invention is decrypted only for the portion encrypted by the scrambler. Since the conversion processing is performed, it is possible to correctly decode.

[0024]

1 is a block diagram of a scrambler according to a first embodiment of the present invention. In FIG.
Reference numeral 11 is a dividing device, 12 is an encrypting device, and 13 is a combining device. The operation of the scrambler according to the first embodiment of the present invention will be described below with reference to the drawings.

As a processing target, it is assumed that a digital video signal packetized after the compression processing is used as input data and is processed for each packet. First, the dividing device 1
1 outputs the data at the position to be encrypted from the input data as the encrypted data. Here, the size of the encrypted data is equal to the size of the encrypted block in the encryption device 12. The dividing device 11 extracts one or more pieces of encrypted data from one packet of the input data so that one piece of encrypted data does not extend over a plurality of packets.

Next, the encryption device 12 inputs the key and the data to be encrypted output from the dividing device 11, performs the encryption by the block encryption method under the control of the input key, and outputs as the encrypted data. Output. Next, the synthesizer 13
Inputs the input data and the encrypted data output from the encryption device 12, combines them, and outputs them as an output video signal. At this time, the synthesizing device 13 synthesizes the encrypted data at the position where the encrypted data is taken out by the input data dividing device 11.

The operation of the scrambler according to the first embodiment will be described below in more detail with reference to the drawings.

FIG. 3 is an explanatory diagram showing a portion to be encrypted in the packet of the input data of the scrambler in the first embodiment. FIG. 3A shows a packet of input data packetized after being compressed by transform coding, and 31 is control data used for controlling communication.
Reference numeral 32 is a DC component, and 33 is an AC component. Here, it is assumed that the AC components 33 are arranged so that the left side is a low frequency component and the right side is a high frequency component. Also, FIG.
(B) shows an encryption processing position, 34 is a data position where encryption is not performed, and 35 is a block showing an encrypted data position.

As shown in FIG. 3, encrypted data position 3
Reference numeral 5 includes all parts of the DC component 32 and part of the AC component 33, and the dividing device 11 divides the data at the encrypted data position 35 from the input data and outputs it as the encrypted data.

As described above, according to the first embodiment, the DC component of the image is always subjected to the encryption process. Therefore, even if the DC component is randomized and there is a portion which is not encrypted, it is It is an AC component only. When an image is formed from data divided into frequency components, the image is formed using the AC component with the DC component as the reference, but in this case, the reference DC component is randomized, so the AC Even if the components are correct, the formed image will be distorted.

Further, the encryption is performed by the block encryption method, and the confidentiality of the encrypted part is sufficient.
Therefore, it is difficult to infer the original image from the scrambled image, and it is possible to realize a scrambler that can obtain sufficient confidentiality.

In the scrambler according to the first embodiment, the DC component 3 as shown in FIG.
2 shows the case where the packet data in which the AC component 33 and the AC component 33 are lined up is processed, but if the configuration is such that all the DC components and some of the AC components are encrypted, It goes without saying that the components 33 may be arranged in any manner and the same effect can be obtained. An example showing the encrypted data position 35 when the DC component 32 and the AC component 33 are arranged differently is shown in FIGS. 4 and 5.

Further, in the scrambler of the first embodiment, the encrypted data position 35 is selected as shown in FIG. 3B, but all of the DC component 32 and part of the AC component 33 are selected. If it is configured to be selected, FIG. 6 (b)
Other positions may be selected as shown in, and the same effect can be obtained.

In the scrambler according to the first embodiment, all of the DC components and some of the AC components are encrypted. However, even if the configuration is such that only the DC components are encrypted, Similar effects are obtained because the components dominate most of the features of the reproduced image.

In the scrambler according to the first embodiment, all the DC components are encrypted, but even if the lower few bits are not encrypted, if the remaining upper bits are encrypted, a little picture is obtained. Is inferior in stirring property,
Almost the same effect can be obtained.

Next, a second embodiment of the present invention will be described with reference to the drawings. The scrambler of the second embodiment has the same configuration as that of the first embodiment shown in FIG. 1, and therefore detailed description thereof will be omitted. However, the input data and the operation of the dividing device 11 will be omitted. Is different from the first embodiment, and this point will be described in detail with reference to the drawings.

FIG. 7 is a diagram showing a portion to be encrypted in the packet of the input data of the scrambler in the second embodiment. FIG. 7A shows a packet of input data packetized after being compressed by variable length coding, and 71 is control data used for communication control,
2 is fixed length data and 73 is variable length data. Here, the left side of the variable length data 73 is the first bit.

FIG. 7B shows an encryption processing position, 74 is a data position where encryption is not performed, and 75 is a block showing an encrypted data position. As shown in FIG. 7, the encrypted data position 75 is the fixed length data 72.
Of the variable length data 73 and the beginning of the variable length data 73.
The data of No. 5 is divided and output as encrypted data.

As described above, according to the second embodiment, all fixed length data and the beginning of variable length data are always encrypted. Variable length coded data has 1 in it
If there is an error in a bit, after the code including the error, in the worst case, the error is propagated until it is refreshed.
The encrypted part of the variable-length code is converted into a random value outside the stipulations of the variable-length code, and is therefore treated like an erroneous code. Therefore, even if there is an unencrypted part in the latter half of the variable-length code, it is highly likely that that part will also be judged as an incorrect code. As a result, the scramble device that can obtain higher confidentiality can be configured.

In the scrambler of the second embodiment, all fixed-length data and variable-length data are encrypted at the beginning, but there is no fixed-length data in the packet to be processed. In this case, it goes without saying that the same effect can be obtained if the variable length data is always encrypted at the beginning.

In the scrambling device of the first and second embodiments, the dividing device 11 and the synthesizing device 13 are provided as separate devices, but the input data transferred at one time is encrypted. If it is smaller than the size of the encrypted block in the device 12, the dividing device 11 and the synthesizing device 13 require a delay device. At this time, if the dividing device and the synthesizing device are configured by one device, the delay device can be shared and the same effect can be obtained.

In the scrambler of the first and second embodiments, the control data is not encrypted, but it is used in the communication path between the scrambler and the descrambler. If the data is not present, it may be encrypted, and the same effect can be obtained, and the effect of further increasing the confidentiality can be obtained.

FIG. 2 shows the configuration of a descrambling device according to the third embodiment of the present invention. In FIG. 2, 21
Is a dividing device, 22 is a decoding device, and 23 is a synthesizing device. The operation of the descrambling device according to the third embodiment will be described below with reference to the drawings.

The object of the processing is the data after the packetized digital video signal is scrambled by the scrambler of the first embodiment or the second embodiment after the compression processing, It is assumed that each packet is processed.

First, the dividing device 21 extracts the data at the position to be decoded from the input video signal as the data to be decoded and outputs it. At this time, the dividing device 21 sets the encrypted data in the synthesizing device 13 in the scramble device shown in FIG. 1 as the decrypted data. Next, the decryption device 22
Receives the key and the decrypted data output from the dividing device 21, performs the decryption process by the block encryption method under the control of the key, and outputs the decrypted data.

At this time, the key input to the decryption device 22 is the same as the key used in the encryption device 12 of the scramble device when the data to be processed is scrambled, and the decryption device The decryption process performed at 22 is an inverse conversion of the encryption process performed on the decrypted data. Next, the synthesizer 23 receives the input data and the divider 21.
The output non-encrypted data is input, and the input data and the decrypted data are combined and output as an output video signal.
At this time, the synthesizing device 23 synthesizes the decoded data at the position where the data to be decoded is taken out by the input data dividing device 21.

As described above, according to the third embodiment, the first
With respect to the packet scrambled by the scrambler according to the first embodiment or the second embodiment, only the part encrypted by the scrambler is decrypted, so that the packet can be correctly decrypted.

In the descrambling device of the third embodiment, the dividing device 21 and the synthesizing device 23 are provided as separate devices. However, if they are configured by one device, the delay device can be shared, Further, the same effect can be obtained.

[0049]

As described above, according to the first aspect of the present invention, the digital video signal packetized after the compression processing by the transform coding is processed and the block cipher processing in the packet is applied. It is possible to configure a scramble device that can obtain sufficient confidentiality, and its practical effect is great.

Further, according to the second aspect of the invention, the digital data packetized after the compression processing by the variable length coding is targeted for processing, and sufficient confidentiality is maintained in the application of the block cipher processing within the packet. The resulting scrambler can be configured.

Further, according to the third invention, it is possible to configure a descrambler capable of correctly decoding the digital video signal scrambled by the scrambler of the first and second inventions.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a scrambler according to a first embodiment and a second embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a descrambling device according to a third embodiment of the present invention.

FIG. 3 is a diagram showing an encryption position of the scrambler in the first embodiment of the present invention.

FIG. 4 is a diagram showing an encryption position of a scrambler in the embodiment.

FIG. 5 is a diagram showing an encryption position of the scrambler in the embodiment.

FIG. 6 is a diagram showing an encryption position of a scrambler in the embodiment.

FIG. 7 is a diagram showing an encryption position of a scrambler in the second embodiment of the present invention.

FIG. 8 is a diagram showing a video packet of a digital video communication system in a conventional example.

FIG. 9 is a diagram showing a video packet of a digital video communication system in a conventional example.

FIG. 10 is a diagram showing an encryption position of a scrambler in a conventional example.

FIG. 11 is a diagram showing an encryption position of a scramble device in a conventional example.

[Explanation of symbols]

 11, 21 Splitting device 12 Encryption device 13, 23 Compositing device 22 Decryption device 31, 71 Control data 32 DC component 33 AC component 34, 74 Unencrypted data position 35, 75 Encrypted data position 72 Fixed length data 73 Variable length data

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hironori Murakami 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] 1. A digital video signal divided into packets after being subjected to compression processing by transform coding is processed, the packets are used as input data, and at least a DC component in the packets is block-encrypted. A scrambler characterized by encryption according to a method. 2. A dividing device for inputting a packet, extracting data to be encrypted from the packet and outputting the packet, and inputting the data to be encrypted, performing encryption processing by a block encryption method, and encrypting the result. An encryption device that outputs as encrypted data; and a synthesizing device that inputs the encrypted data and the packet and replaces the encrypted data of the packet with the encrypted data. 2. The scrambler according to claim 1, wherein the data to be encrypted that is taken out has a size that is an integral multiple of an encryption block that is processed in the encryption device and that includes at least a DC component of a video signal. 3. The scrambler according to claim 1, wherein a part of the low frequency components of the DC component and the AC component in the packet is encrypted by a block encryption method. 4. When the dividing device extracts the encrypted data from the packet, the encrypted data includes a part of the low frequency component of the DC component and the AC component of the video signal. The scrambler according to item 2. 5. The digital data packetized after being compressed by a variable length code is processed, and at least the first few bits of the variable length code are encrypted by a block encryption method. Scrambler. 6. A dividing device for inputting a packet, extracting data to be encrypted from the packet and outputting the packet, and inputting the data to be encrypted, performing encryption processing by a block encryption method, and encrypting the result. It comprises an encryption device for outputting as encrypted data, and a synthesizing device for inputting the encrypted data and the packet and replacing the encrypted data of the packet with the encrypted data. 6. The scrambler according to claim 5, wherein the encrypted data to be encrypted has a size that is an integral multiple of an encrypted block processed in the encryption device, and includes at least some leading bits of a variable length code. apparatus. 7. A packet after being scrambled by the scrambler according to any one of claims 1, 3, and 5 is targeted for processing, and a portion encrypted by the scrambler is A descrambling device, which performs reverse conversion of encryption performed by the scramble device by a block encryption method. 8. A packet after being scrambled by the scrambler according to any one of claims 2, 4, and 6 is targeted for processing, a packet is input, and decoded data is extracted from the packet. A dividing device for extracting and outputting the data to be decrypted, a decryption device for performing decryption processing by a block cipher method and outputting the result as decrypted data, and inputting the decrypted data and the packet Then, the decryption data in the packet is replaced with the decryption data, and the decryption data extracted from the packet in the dividing device corresponds to the encryption data in the scrambler. This is position data, and the decryption process performed by the decryption device is the same as the encryption process performed by the scramble device. Descrambler, which is a transformation.