JPH02128585A - Data transmitting system - Google Patents

Abstract

PURPOSE:To keep the secret of transmitted data without increasing transmitting time in a transmitting system which transmits plural kinds of transmitting data after compressing and extracting the data by ciphering some kinds of transmitting data. CONSTITUTION:The data transmitting device 1 of this data transmitting system is a video telephone set, etc., which performs picture data transmission and reception through, for example, telephone lines 2 and 22, and is provided with a transmitting means 5 which transmits picture data picked up by an image pickup device 3 to the telephone line 2 after encoding and a receiving means 6 which receives the data transmitted from the transmitting means 5 and displays the data in a displaying section 7 after decoding. An encoding circuit 11 performs a compression process on picture data by dividing the picture data into plural sections and selecting the mean value and variance of each section and identification data to be respectively added to plural kinds of representative data selected in connection with the state of data at each section, and the mean values are ciphered. Therefore, the transmitting data can be ciphered and decoded in short time as compared with the case where the ciphering process is performed to all transmitting data.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is suitably implemented in, for example, video telephones,
The present invention relates to a data transmission method that compresses data to be transmitted and extracts and transmits multiple types of transmission data.

2. Description of the Related Art In recent years, technologies for transmitting image data, such as facsimile machines and video telephones, have become increasingly important. However, image data has a high degree of redundancy, and data compression technology is essential for transmitting it in a short time. Also,
In connection with protecting the security of transmitted image data, there is also an increasing demand for confidential communication.

When using the mean value separation normalization vector quantization encoding method, which is one of vector quantization which is an excellent data compression technique, image data is first divided into a plurality of sections.

Three types of encoded data are created and transmitted: average value data for each section, normalized value data that is the variance of each section, and an identification code for specifying a representative vector, which will be described later. Ru. A representative vector is representative data representing a plurality of data types in one section, and an identification code is attached to each representative vector. The correspondence between the identification code and the representative vector is called a codebook or the like.

When performing confidential communication, the three types of encoded data are subjected to encryption processing such as data rearrangement, which is called scrambling, in order to add a security function. On the receiving side, the encrypted data is decoded and the three types of encoded data described above are further decoded. That is, arithmetic processing based on average value data and normalized value data is performed on the representative vector corresponding to the identification code, and an image close to the original image is reproduced.

Problems to be Solved by the Invention In the data transmission system of the prior art described above, all three types of encoded data are encrypted, so the processing time for decoding these three types of encoded data is long. There is a problem in that it takes a long time to restore and reproduce the image.

Therefore, an object of the present invention is to provide a data transmission method that reduces processing time for encrypting transmitted data and improves data transmission speed.

Means for Solving the Problems The present invention provides a method for compressing data to be transmitted, extracting and transmitting a plurality of types of transmission data, and encrypting a portion of the types of data of the plurality of types of transmission data. This is a data transmission method characterized by the following.

Further, in the present invention, the data to be transmitted is image data, the image data is divided into a plurality of sections, and a plurality of sections are selected regarding the average value, variance, etc. of each section, and the data format of each section. This data transmission system is characterized in that compression processing is performed by selecting identification data attached to each type of representative data, and the average value is encrypted.

According to the present invention, in a method of compressing data to be transmitted and extracting and transmitting a plurality of types of transmission data, a portion of the types of data of the plurality of types of transmission data are encrypted. Therefore, it is possible to encrypt and decrypt the transmitted data in a shorter time than when encrypting all the transmitted data.

For example, if the data to be transmitted is image data, the image data is divided into multiple sections. As the transmission data, the average value, variance, etc. in each section, and identification data attached to each of a plurality of types of image data selected regarding the data format of each section are selected.

Compression processing is performed by such selection of transmission data.

According to the present invention, encryption processing is performed on the average value. In such cases, the average value has low redundancy and the actual amount of information is large, so the effect of encryption is large.
Moreover, there is no need to encrypt other types of transmitted data.

Therefore, it is possible to perform encryption and decryption in a short time while maintaining a sufficient security function.

Embodiment FIG. 1 is a block diagram showing the basic configuration of a digital transmission device 1 according to an embodiment of the present invention. Data transmission device 1
is, for example, a video phone that transmits and receives image data via telephone lines 2 and 22, and includes a transmitting means 5 that encodes the image data captured by the imaging device 3 and transmits it to the telephone line 2, and a transmitting means. receiving means 6 for receiving transmission data transmitted from 5, decoding the transmission data, and displaying the decoded data on a display section 7.

In the transmitting means 5, the imaging device 3 is, for example, a CCD.
(Cbarge Coupled Device), has a resolution of, for example, 256 x 25'6 pixels, and outputs image data having 256 levels of gradation in each pixel to the encoding circuit 11.

The encoding circuit 11 converts such image data into a format shown in FIG.
), a plurality of partitions By(y=(i-1)
・Divide into (n+j, i=1 to m, j-1 to n). As shown in FIG. 2 (2), each section By is composed of 4×4 pixels bx (x=1 to 16), and the encoding circuit 11 is configured to adjust the gradation level of the pixels in each section By. The average value data AVy and the variance SDy are calculated, and an identification code idy is selected as described later.

That is, the storage circuit 9 realized by, for example, a read-only memory has 256 representative data formats (hereinafter referred to as "representative vectors") C1] of 8 gradations corresponding to a 4×4 pixel bx. identification code 1].

Furthermore, the encoding circuit 11 selects a representative vector that has the minimum error from the representative vector in the section By by a calculation described later, and outputs an identification code idy corresponding to the representative vector. The identification code idy and the normalized value data SDy, which is the variance, from the encoding circuit 11 are output to the transmitting circuit 16. Also,
The average value data Avy from the encoding circuit 11 is subjected to an encryption process called, for example, scrambling by the encryption circuit 10, and is converted into average value data AVP1. The signal is then output to the transmitting circuit 16.

The transmitting circuit 16 transmits the average value data AVp, normalized value data SDy, and identification code idy to the telephone line 2 as transmission data. The telephone line 2 is connected to a telephone line 22 via an exchange 12 installed at a telephone office or the like, and the transmitted data from the transmitting means 5 is received by the receiving circuit 17 of the receiving means 6. The receiving circuit 17 individually outputs the average value data A V p-5 normalized value data SDy and the identification code idy.
VPy is subjected to decoding processing such as descrambling by the decoding circuit 13, and is provided to the decoding circuit 15 as average value data AV3/. Further, the normalized value data SDy and the identification code idy from the receiving circuit 17 are
It is directly output to the decoding circuit 15.

The memory 14 provided in association with the decoding circuit 15 includes:
The same contents as the memory 9 of the transmitting means 5 described above are stored. The decoding circuit 15 reads the representative vector C1dy from the memory 14 based on the input identification code idy.

For this representative vector Cidy, normalized value data S
Image processing based on Dy and average value data AVy is performed to reproduce an image close to the original image. This image data is provided to a display section 7 realized by, for example, a CR7 display device and displayed on the screen.

The data compression operation in the encoding circuit 11 of the data transmission device 1 will be described below. Figure 6 (1) - Figure 6 (
3) is a histogram showing the relationship between the gradation level of each pixel in each image example and the number of pixels of that gradation level. Each pixel has 256 levels of gradation, and although there are some differences depending on the image, it can be seen that each pixel is distributed over a wide gradation level.

Such image data is divided into sections By by the encoding circuit 11.
In each section By, the average value data AVy is obtained based on the following formula.

(However, in this example, 1=16) Here, (bx)y represents the gradation degree of pixel bx in section By, and is K-16 in this example.

Figures 7(1) to 7(3) correspond individually to Figures 6(1) to 6(3), and in each section By,
Gradation level (bx)y and average value data AVy at each pixel
This is a histogram showing the relationship between the difference (bx)y-AVy and the number of pixels.

In each section By, the gradation level (bx)y of each pixel bx
is a value close to the average value data Avy in the section By, and for example, if all pixels in the section By are reproduced with the average value data AVy, it is possible that an image close to the original image will be reproduced in a simple image. I understand.

The encoding circuit 11 further calculates each section B based on the second equation.
Normalized value data SDy, which is the variance in y, is obtained.

Eh...(2) (However, in this example, K = 16') Figure 8 (1
) to FIG. 8(3) individually correspond to FIG. 7(1) to FIG. 7(3), and the horizontal axis represents the gradation level (b) of each pixel.
x) Difference between y and average value data AVy (bx) y-AVy
is divided by the normalized value data SDy. In this way, by adding the normalized value data SDy representing variations within each section By, it is possible to reproduce an image that is even closer to the original image.

Next, vector quantization processing in the encoding circuit 11 will be explained. The memory 9 stores a codebook, that is, a representative vector ch corresponding to the identification code h. The representative vector Ch individually corresponds to the 16 pixels bx in each section By, and consists of, for example, 3-bit data CX.

The encoding circuit 11 obtains an error (d x ), y expressed by the following equation, based on the average value data AVy obtained by the above-mentioned arithmetic processing and the normalized value data SDy.

Furthermore, with respect to the representative pixel=11 Ch corresponding to each identification code h, the total sum Δh y of errors for each pixel represented by the fourth equation is calculated.

(4) (However, in this embodiment, =16) Here, (c x ) h is the data cx of the representative vector Ch corresponding to the identification code 11.

The encoding circuit 11 outputs the identification code idy corresponding to the smallest representative vector Ci dy of the total error Δatt y to the transmission circuit 16 .

In this way, in the encoding circuit 11, the imaging device 3
The image data from
, and an identification code idy.

Next, the encryption process in the encryption circuit 10 will be explained. In the encryption circuit 10, a permutation table P shown in the following formula is used.
The average value data AV3/ is replaced by , and so-called scrambling is performed.

PL, P2. ..., py, ... are, for example, a predetermined random number sequence, and the encryption circuit 10 uses the average value data A.
Replace Vy with average value data A V p. As a result, the average value data AVy is rearranged and encrypted.

FIG. 4 is a flowchart for explaining the operation of the data transmission device 1 in data transmission.

Referring to FIG. 4, when image data is input from the imaging device 3, the process moves from step n1 to step n2, and the image data input by the encoding circuit 11 is divided into sections B y
Divided into *'.

In step n3, in each section By, the section By
Average value data AV of gradation level (bx)y of pixel bx within
y and normalized value data SDy are calculated.

In step n4, the code book in the memory 9 is referred to and an identification code idy is selected corresponding to each section B)l.

At step n5, the encryption circuit 10 starts scrambling the average value data AVy, that is, rearranging the data for encryption, and at the same time, at step n6, the normalized value data SDy is transmitted. Normalized value data SD
When the transmission of y is completed, the identification code idy is subsequently transmitted in step n7.

A time chart of the processing operations in steps n5 to n7 is shown in FIG. Normalized value data 5I)
l is transmitted during period W1 as shown in FIG. 3(1). In addition, the identification code idy is shown in Figure 3 (2).
It is transmitted during period W2 following period W1 as shown in FIG. During these periods Wl and W2, the average value data A
Encryption processing of vy is performed in parallel. The encrypted average value data A V p- is transmitted in a period W3 following the period W2 in step n8.

When the image shown in FIG. 5(1) is transmitted by such a processing operation, for example, when a third party receives the transmitted data using the receiving means 21 via the line 20 in FIG. Since the average value data Avy has been encrypted, the image is reproduced as shown in FIG. 5(2). According to the inventor's experiments, in the case of image data, the redundancy of the average value data AVy is low;
It turned out that the actual amount of information was large. Therefore, as can be seen from FIG. 5(2), sufficient security can be achieved by encrypting the average value data AVy.

FIG. 9 is a flowchart for explaining the transmission data receiving operation and image displaying operation of the receiving means 6. When the receiving means 6 receives the transmission data from the transmitting means 5,
Moving from step m1 to step m2, descrambling of average value data AVP of the transmission data is started. Furthermore, in step m3, the corresponding representative vector C1dy is read from the memory 14 based on the identification code idy. In step m4, average value data AVy
, the gradation level (ex)y of each pixel bx is calculated by the following equation based on the representative vector C1dy and the normalized value data SDy.

(ex)y-((cx)i dy+AVylXSDy・
(6) In step m5, an image is displayed on the display section 7 based on this gradation (ex)y, and the processing operation is completed.

In this way, in this embodiment, the encryption process is performed only on the average value data AVy of the transmission data, so for example, while the normalized value data SDy and the identification code idy are being transmitted, the average The value data AVy can be encrypted, and substantially no time is required for the encryption process. Therefore, the image data to be transmitted can be encrypted for security protection and transmitted without increasing the transmission time.

In this embodiment, the representative vector ch corresponding to each identification code b is fixed in the memory 9, but it is also possible to create and transmit an optimal representative vector corresponding to each image. Ru. Also, for encryption,
Although we have described the case where scrambling is performed based on permutation table P, multiple random number sequences are prepared, an identification code for selecting one random number sequence from among the random number sequences is transmitted, and a random number corresponding to the identification code is transmitted. It is also possible to configure the column to be used as a replacement table to perform scrambling. Further, the encryption method is not limited to scrambling, and other methods may be used to perform the encryption process, such as adding random number data to average value data, for example.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, in a method for compressing data to be transmitted and extracting and transmitting multiple types of transmission data, security processing can be performed without increasing transmission time. This greatly improves convenience.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a data transmission device 1 according to an embodiment of the present invention, and FIG. 2 shows a plurality of sections of image data By.
FIG. 3 is a time chart when transmitting data in the data transmission device 1, FIG. 4 is a flowchart for explaining the data transmission operation of the data transmission device 1, and FIG. 5 is a time chart before transmission. Figure 6 is a histogram showing the relationship between the gradation of each pixel in each image and the number of pixels, and Figure 7 is a diagram showing an example of an image of each pixel in each image and an image that has been encrypted. Gradation average value data A
A histogram showing the relationship between the difference from vy and the number of pixels,
Figure 8 is a histogram showing the relationship between the mean value separation and normalized gradation of each pixel in each image and the number of pixels.
The figure is a flowchart for explaining the operation of the data transmission device 1 to reproduce an image. 1... Data transmission device, 2, 22... Telephone line, 9
゜14...Memory, 10...Encryption circuit, 11...
・Encoding circuit, 13...Decoding circuit, 15...Decoding circuit, AVy...Average value data, SDy...Normalized value data, idy...Identification code agent Patent attorney Keiichi Nishikyo Department\mouth cccc r town; 1111 rl-1111 ``1-1-1''-m
--1r-1111q) Fight @嬶? Mokajo 8 × S-Yu and ×

Claims (2)

[Claims] (1) A method for compressing data to be transmitted, extracting and transmitting multiple types of transmission data, characterized in that a portion of the types of data of the plurality of types of transmission data are encrypted. Data transmission method. (2) The data to be transmitted is image data, and this image data is divided into multiple sections, and multiple types of data selected regarding the average value, variance, etc. of each section, and the data format of each section are divided into multiple sections. The data transmission method according to claim 1, wherein the compression process is performed by selecting identification data attached to each representative data, and the average value is encrypted. .