JPH088898A - Enciphering device - Google Patents

Abstract

PURPOSE:To reduce the amount of arithmetic operation on both transmission and reception sides without degrading the ciphering secrecy and the cipher intensity by performing encoding only important bits that characterize voice information or the like in encoding an information source, and then performing error detection or the like and the transmission. CONSTITUTION:Appropriate ciphering is performed only to the accoustically characteristic most important bits, CRC codes are calculated and added to them and error correction coding and inter-slot interleave are performed. On the reception side, decoding processings corresponding to the operations are advanced in the opposite order of the encoding and voice data are decoded. Thus, integration is performed while utilizing the features of required low rate encoder, ciphering device and error detection and error correction devices in digital communication and ciphers are made safe and easily realizable. That is, since the ciphering is performed only to the characteristic important bits, making into a hardware is facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encryption device, and more particularly to an encryption and decryption device used for digital communication of voice and images.

[0002]

2. Description of the Related Art Generally, when performing communication of digitized signals, it is often necessary to perform low-rate coding, as well as error detection and correction, interleaving and encryption. The coding side configuration of such a system is generally as shown in FIG. In this method, all bits are often encrypted and decrypted.

That is, as in the example of FIG. 2, VSELP (Vector
20 msec. By a speech coder (200) such as Sum Excited Linear Predictive method. Per 134
The bit-encoded signal is distributed to the following parameters according to importance by the bit distributor (201) based on the characteristics of the audio information.

A) most important bits for hearing: 44 bits b) important bits: 31 bits c) less important bits: 59 bits then a. From the above, a CRC (Cycle Redundancy Check) encoder (202) calculates 7-bit CRC error detection bits, and a. + B. 75 bits and 5 tail bits are combined and convolutionally coded in the (203) section to form a 165-bit signal. And
In part (204) c. After being combined with, the bit is interleaved with other slots in the (205) part. Then, all the data of 224 bits per slot as a result of this is subjected to predetermined encryption in the (206) section in the subsequent stage. On the receiving side, in the reverse order of this operation, the ciphertext is first decrypted into plaintext, and then deinterleaved, error corrected, error detected, and voice decoded.

FIG. 3 illustrates an encoding procedure according to this conventional method. As shown here, after calculating the CRC bits, error correction coding and bit interleaving between slots are performed, and all bits of the output data are encrypted.

[0006]

In the above-described encryption, when a 224-bit plaintext per slot is subjected to, for example, DES or FEAL encryption / decryption, a 64-bit unit calculation is required. Since it has to be performed once, the amount of calculation becomes large, which is disadvantageous for application to a system that requires real-time processing. Moreover, since the CRC code for error detection is calculated after encryption for the most important bits, there is a risk that this CRC error detection code will be used as auxiliary information when decrypting the code, and this is a factor that deteriorates the encryption strength. Becomes

[0007]

The present invention has been made to solve the above problems. Utilizing the characteristics of coded digital signals of voice and images, the amount of calculation is small,
In addition, it is to provide a highly secure encryption device.

That is, in the encryption device according to the present invention, only the important bits that characterize voice and image information in the encoded information source are encrypted, and then the CRC or FEC is used.
By performing error detection and error correction coding as described above and transmitting, the amount of calculation on both the transmitting and receiving sides is reduced without deterioration of the encryption confidentiality and encryption strength.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 is a block diagram showing an embodiment of the present invention, and assumes the case where VSELP is used as a voice encoding system. However, it corresponds to the inside of the baseband coding apparatus in FIG. 1 in the entire system.

20 mse of the output of the speech encoder (400)
c. Similar to the conventional method, the 134 bits per hit are first set by the bit distributor (401) by a (4
It is divided into 4 bits), b (31 bits), and c (59 bits). This a. First, the encryption is applied in the (406) part. As the encryption algorithm at this time, DES, FEAL, or the like can be applied, and normally, in addition to the purpose in a specific bit unit in CFB (Cipher Feedback Mode) mode as shown in FIG. 6 or OFB (Output Feedback Mode). Encrypt in chain mode according to the purpose. Next, regarding this encrypted output, the CRC bits of 7 bits are calculated in the (402) section, and b. Together with the total of 75 bits of information and 5 bits of tail bits, error correction coding such as convolutional coding is performed in the (403) section to obtain 165 bits. Then, in section (404), c.
Is bit-combined to form 224 bits, and bit interleaving is performed on a slot-by-slot basis in the (405) section and output.

FIG. 5 is a diagram showing a processing procedure executed in the example of FIG. That is, first, appropriate encryption is performed only on the most important bit that is auditory characteristic, and a CRC code is calculated and added to this, and error correction encoding and inter-slot interleaving are applied. .

On the receiving side, the decoding process corresponding to each of the above operations is carried out in the reverse order of encoding to decode the audio data.

The above description is for one example, and the present invention is not limited to this. That is, the number of bits and the bit allocation in each frame are not limited to the above, and the case where the bit distributor is provided in the audio encoder is also targeted, and the encoding method, the encryption method, the encryption method, and the encryption method of the voice, etc. Whether or not the chain mode is applied, its type, and applicable bit range are not limited. Further, the types of error detection codes and error correction coding systems, the bits to which they are applied, the presence or absence of interleaving, and the way of applying them are not limited.

[0014]

EFFECTS OF THE INVENTION By using the present invention, in digital communication such as voice or image, the low rate encoder, the encryption device, the error detector and the error corrector are integrated while making the most of them. It is a device that is secure and easy to implement as encryption. That is, it is advantageous in the following points as compared with the conventional device.

1. This check bit cannot be used as decryption information to calculate the error detection code after encryption.

2. Since only the important bits that are characteristic of voice and image information are encrypted, the amount of calculation required for the encryption and decryption is small, hardware is ready, and the feasibility for a system that requires real-time performance high.

3. The total number of keys does not change in encryption. Moreover, since the number of bits to be encrypted per key is reduced, the attack against the ciphertext is stronger. Further, when adopting a chain technique such as OFB and CFB, the encryption strength can be further increased by changing the initial value of the register in the inside at an appropriate frequency.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a voice digital communication system.

FIG. 2 shows a relationship between a configuration of a conventional speech encoding device and an encryption device.

FIG. 3 shows an encoding processing procedure by conventional voice encoding and encryption.

FIG. 4 illustrates the relationship between the configuration of a voice encoding device according to the present invention and an encryption device.

FIG. 5 shows a coding processing procedure by voice coding and encryption according to the present invention.

FIG. 6 illustrates a general chaining technique in encryption.

[Explanation of symbols]

200,400 Speech coder (VSELP etc.) 201,401 Bit distributor 202,402 CRC coder 203,403 Convolutional coder 204,404 Bit combiner 205,405 Inter-slot bit interleaver 206, 406 Encryption device 210,410 Channel coder

Claims (9)

[Claims] 1. An encryption device for encrypting digital data: distribution means for distributing predetermined data to be encrypted of the digital data and residual data other than the digital data, and the data to be encrypted. An apparatus comprising: an encryption means for performing encryption processing on the encrypted data and outputting encrypted data; and a channel coder including means for combining the encrypted data and data other than the above. 2. A plurality of voice parameters are calculated from a signal obtained by encoding a voice signal into digital data, and only the bits determined from the plurality of voice parameters are extracted to be encrypted and the predetermined number is determined from the plurality of voice parameters. A voice encoding device having a function of distributing residual data with bits removed, an encryption means for performing an encryption process on the data to be encrypted and outputting the encrypted data, and following this output, this encryption A voice encoding / decoding device for performing an encryption process, comprising a channel coder including means for combining data and the residual data. 3. An encryption device for performing an encryption process on digital data, comprising: a separation means for separating predetermined encryption technique data from the digital data and other data, and the encryption device. An encryption device comprising: an encryption unit that performs an encryption process on data to be output and outputs the encrypted data; and a combining unit that combines the encrypted data and the other data. 4. A plurality of voice parameters are calculated from a voice digital signal obtained by converting a voice signal into a digital signal, and the data to be encrypted by extracting a predetermined bit from the plurality of voice parameters and the plurality of voice parameters. A speech coder that separates the remaining data from which the predetermined bits have been removed, an encryption unit that performs an encryption process on the data to be voiced, and outputs encrypted data, the encrypted data and the A vector sum excitation linear predictive coding device having an encryption device, characterized in that it comprises a channel coder for combining arithmetic and data. 5. An apparatus as claimed in claim 1 or 2, wherein the channel coder comprises means for adding a CRC code to the combined data. 6. The encryption device according to claim 1, wherein the channel coder includes means for further FEC (error correction) encoding the CRC code added data. apparatus. 7. The channel coder performs FEC (error correction) coding on the data to which the CRC code is added,
Device for coupling to an encryption device according to claim 1 or 2, characterized in that it further comprises bit interleaving means. 8. The apparatus of claim 4, wherein the channel coder includes means for adding a CRC code to the combined data. 9. The apparatus of claim 8, wherein the channel coder comprises means for further convolutionally encoding the CRC coded data.