JPH10257031A - Enciphered communication method and equipment therefor and enciphered communication transmitter-receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve secrecy by transmitting key signals at the time of ciphering source signals and the ciphered signals of the source signals by respectively different modulation systems, respectively receiving and demodulating them and decoding and reproducing the ciphered signals by the key signals. SOLUTION: Signals Dd for which analog input source signals to be transmitted are converted by an A/D converter are divided for respective bits, turned to block units and numbered. After they are rearranged and ciphered in a rearrangement part and serial/parallel converted in an S/P change part as the signals Dd', even-numbered and odd-numbered block data strings are set to carrier frequencies f11 and f12 and they are transmitted through ASK modulation parts 11 and 12 whose modulation degree is controlled at random in a control part. In the meantime, the key signals KY at the time of rearranging the digital signals Dd to the signals Dd' are transmitted by sending even- numbered blocks to an FSK modulation part 21 and odd-numbered blocks to the FSK modulation part 22 set to the different carrier frequencies f21 and f22 through the control part and an S/P conversion part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a confidential communication method capable of imparting confidentiality to transmission / reception signals. The present invention relates to a device and a secret signal transmitting / receiving device.

[0002]

2. Description of the Related Art Conventionally, a scramble system or a spread spectrum system has been used as a concealment system for transmitting and receiving signals wirelessly. As another method, for example, as disclosed in Japanese Patent Laid-Open No. 4-304727, a baseband frequency is changed in accordance with an encryption rule, this is phase-modulated and frequency-modulated, and an encryption rule is phase-modulated. There is a method in which a single carrier is added to each frame and transmitted. FIG. 7 shows the configuration of Japanese Patent Application Laid-Open No. 4-304727. The data input from the data input unit is encrypted by changing a clock frequency for forming a baseband signal according to a rule (encryption unit), and the PSK (Phas
e Shift Keying) Performs modulation and further FSK
(Frequency Shift Keying)
The signal is modulated by SK, combined, and transmitted on a single carrier.

[0003]

In the above-mentioned conventional concealment method, confidentiality is ensured by using a key signal for demodulating a scrambled signal and a PN code serving as a key for demodulating a spread spectrum signal. Or multiplex-modulate a baseband signal or a key serving as an encryption rule to ensure confidentiality.

[0004] However, since each system has a single carrier, there is a problem that if the carrier is intercepted, it may be decoded later because of a signal processing problem.

[0005] An object of the present invention is to provide a confidential communication method that enhances confidentiality by transmitting an original signal to be transmitted and a key signal using different modulation schemes. An object of the present invention is to provide a device and a secret signal transmitting / receiving device.

[0006]

FIG. 1 shows a basic configuration diagram of a secret communication device according to the present invention.

[0007] The original signal to be transmitted is encrypted by the key signal. The encrypted signal is modulated by the first modulator and transmitted, and the key signal is modulated by the second modulator and transmitted. At this time, the modulation schemes of the first modulation unit and the second modulation unit are different from each other. On the other hand, the receiving side receives and demodulates the transmitted signals of different modulation schemes, decrypts the received encrypted signal based on the demodulated key signal, and reproduces the original signal.

As described above, by transmitting the encrypted signal and the key signal using different modulation schemes, a receiving apparatus capable of demodulating the modulated signal by recognizing the modulation scheme for reproducing the original signal. Is needed. For this reason, confidentiality is significantly improved.

The encryption of the original signal can be performed by rearranging the original signal. For example, if the original signal to be transmitted is a data sequence, the data is rearranged for each specific block. The data representing the contents of the rearrangement at this time is used as key data.

Further, by multiplexing one or both of the transmission frequencies of the encrypted signal and the key signal, the confidentiality can be further enhanced. For example, the encrypted data is divided into blocks, the even blocks are transmitted at the first frequency, the odd blocks are transmitted at the second frequency, the key data corresponding to the even blocks are transmitted at the third frequency, and the key data corresponding to the odd blocks are transmitted. By transmitting on the fourth frequency,
Four frequencies are used in all, and the confidentiality is further improved.

[0011] The encryption of the original signal to be transmitted further includes changing the modulation factor at the time of transmission. The key signal in that case is a signal indicating the change in the modulation factor. If the degree of modulation at the time of transmission is changed and the rearrangement of the original signals is performed at the same time, the confidentiality is further improved.

[0012]

FIG. 2 shows a block diagram on the transmitting side and a block diagram on the receiving side of the secure communication device according to the present invention.

Assuming that an original signal to be transmitted is analog data, the input analog data is converted into an analog signal by an A / D converter.
The data is D-converted, and the data is further divided into bits to form a block unit, and numbering of each bit is performed for each block. FIG. 3A shows a, b, c,.
FIG. 3B shows a state in which a data string divided for each bit is numbered from 1 for each block of 4 bits. Next, the numbered data strings are rearranged randomly. FIG.
(C) shows the state after the rearrangement. By this rearrangement, the first encryption is performed. The rearranged encrypted signal is subjected to ASK (Amplitude Shift Keying) modulation after being subjected to serial / parallel conversion in the S / P changing unit and transmitted. In this embodiment, even-numbered blocks (even
The block) data string is sent to the ASK modulation section 11, and the odd block (odd block) data string is sent to the ASK modulation section 12.
Sent to The carrier frequencies of the ASK modulators 11 and 12 are set to different values (f11, f12). The modulation degree in each of the ASK modulators 11 and 12 is randomly controlled by the controller. As described above, the second encryption is performed by providing two stages of the ASK modulation unit and multiplexing the transmission frequency, and the control unit changes the degree of modulation in each ASK modulation unit at random, thereby obtaining the third encryption. Encryption.

The information for rearranging the digital signal Dd to Dd 'in the rearranging section is input to the control section as a key signal KY. The key signal KY is obtained by picking up only the number of each bit shown in FIG. The controller sends this key signal KY to the S / P converter, where the same key signal is subjected to serial / parallel conversion, and the key signal corresponding to the even-numbered block is sent to the FSK modulator 21 to generate a key corresponding to the odd-numbered block. The signal is sent to FSK modulation section 22.
The carrier frequencies of the FSK modulators 21 and 22 are set to different values (f21, f22). The control unit further converts the signal representing the change in the modulation degree set by the ASK modulation units 11 and 12 into a digital signal and sends the digital signal to the S / P conversion unit, and the modulation degree change signal corresponding to the even-numbered block is transmitted to the FSK modulation unit 21. The FSK modulator 22 modulates the modulation degree change signals corresponding to the even-numbered blocks and transmits the modulated signals.

As described above, the analog data to be transmitted is first encrypted by rearrangement, secondly by frequency multiplexing, and thirdly by encryption degree change. I am trying to do it. And
Since the key signal for decrypting the encryption is transmitted by FSK modulation, which is a modulation method different from ASK modulation, which is a modulation method for transmitting the encrypted signal, confidentiality is extremely enhanced.

In the receiving section shown in FIG. 2B, the encrypted signal is demodulated by demodulating sections (DEM) 11 and 12, and the key signal is demodulated by demodulating sections (DEM) 21 and 22, respectively. Is done. At this time, each demodulation unit needs to correspond to the modulation unit in the transmission unit. That is, DE
M11 and M12 need to be able to demodulate an ASK-modulated encrypted signal.
It is necessary to have a configuration capable of demodulating the SK-modulated key signal. Note that ASK modulation is the same as normal AM modulation, and FSK modulation is the same as normal FM modulation. Therefore, each DEM can use a known DEM. D
The key signals demodulated by the EMs 21 and 22 are parallel-serialized by the P / S converter and passed to the controller. If the demodulated key signal is control data representing a change in the modulation factor, the control unit demodulates the encrypted signals received by the DEMs 11 and 12 using the change signal in the modulation factor. If the modulation degree change signal at this time corresponds to an even block, the modulation degree change signal is passed to the DEM 11, and if the modulation degree change signal corresponds to an odd block, it is passed to the DEM 12. On the other hand, the encrypted signal demodulated in this manner is subjected to parallel / serial conversion in the P / S conversion unit, and is converted into a signal Dd ', which is guided to the rearrangement unit. The rearranging unit includes a memory M, and waits for a certain amount of the signal Dd 'to be stored in the memory M. On the other hand, if the key signal is a signal indicating the content of the rearrangement, that is, a control signal for the rearrangement,
The signal is guided to the reordering unit via the control unit. The rearrangement control data is also sequentially stored until a predetermined amount is stored in the memory M. At a stage where a certain amount is accumulated, the signals Dd 'are rearranged based on the rearrangement control data. That is, the bits are rearranged so that the number added to the head of each bit is 1, 2, 3, and 4, and the data is returned to the original data string shown in FIG. The signal Dd thus returned to the original state is output as the original analog data Da after being D / A converted by the D / A converter.

FIG. 4 is a flowchart showing a transmission procedure on the transmission side shown in FIG.

That is, when analog data Da, which is an original signal to be transmitted, is input, the signal is A / D converted, and numbering and rearrangement are performed for each bit.
(ST2). The rearrangement control data at this time is transmitted by the FSK modulation method after the S / P conversion (ST5). The signal Dd 'encrypted by the rearrangement is S / P
After the conversion, each block of the data sequence is modulated by the ASK modulator 11 or 12 and transmitted. Further, the modulation degree at that time is randomly changed by the control unit, and the control data of the modulation degree, which is a signal indicating the change in the modulation degree, is subjected to S / P conversion, then FSK modulated, and transmitted (ST12). ).

FIG. 5 is a flowchart showing the operation on the receiving side.

On the receiving side, the DEMs 21 and 22 receive rearrangement control data, which is a signal representing the contents of the rearrangement,
After demodulation, the signal is P / S converted and stored in the memory M of the rearrangement unit (ST22). The encrypted signal is D
When received by the EMs 11 and 12 (ST23), control data of the modulation is also received by the DEMs 21 and 22 (ST2).
9), while synchronizing with the P / S converted version,
The encrypted signal is demodulated based on the control data of the modulation factor (ST24). Further, this demodulated signal is represented by P /
The signal is converted into a signal Dd 'by S conversion, and the signal is stored in the memory M of the rearranging unit (ST26). When a predetermined amount of the signal Dd 'and the rearrangement control data are accumulated in the memory M, the data Dd' is synchronized with the data Dd 'based on the control data.
Is returned to the original state (ST27). After the above processing is completed, the data is D / A converted and then reproduced and output as original analog data Da (ST28).

In the above embodiment, since the rearrangement, the multiplexing of the frequency, and the triple encryption by changing the modulation factor are performed, the confidentiality is extremely high. Just adopting one encryption method,
As long as the modulation scheme of the encrypted signal and the key signal is changed, it is possible to obtain considerably high confidentiality. Further, in the embodiment, the frequency multiplexing is performed by providing two stages of each modulation unit. The data sequence of the even-numbered block is modulated by the ASK modulation unit 11, and the data sequence of the odd-numbered block is modulated by the ASK modulation unit 12. This is set randomly, and the set content is transmitted to the key signal. It is also possible to transmit to the receiving side. In this case, since the encryption is further enhanced, the confidentiality is further enhanced. Further, the device shown in FIG. 2 is a communication device in which a transmitting unit and a receiving unit are integrated, but FIG.
Or the configuration shown in FIG. The former is a secret signal transmitting device, and the latter is a secret signal receiving device.

Further, although the confidential communication device shown in FIG. 2 handles digital signals, it can also be configured to handle analog signals as shown in FIG. That is, in FIG. 6, while the analog input signal is modulated by the first modulation method, FM modulation (frequency modulation), and output, the modulation degree is changed at random or at a predetermined change rate, and the modulation degree is changed. A signal representing the change is subjected to PM modulation (phase modulation) as a key signal and transmitted. The carrier of the FM modulator is f1, PN
The carrier of the modulation unit is f2. The receiving side receives the encrypted signal and the key signal, respectively, and demodulates the decrypted encrypted signal.

[0023]

According to the present invention, since the modulation scheme of the encrypted signal and the key signal are made different, even if another person receives this, the first condition for decoding the content is that Since it is necessary to demodulate at least two types of unknown signals, the confidentiality is extremely high as compared with the conventional method of demodulating one type of signal.

In addition, the original signal to be transmitted is rearranged, the frequency is multiplexed, and the modulation is changed by changing the degree of modulation at the time of transmission. There is an advantage that can be raised.

[Brief description of the drawings]

FIG. 1 shows a basic configuration diagram of a secret communication device according to the present invention.

FIGS. 2A and 2B are a block diagram on the transmitting side and a block diagram on the receiving side, respectively, of the secure communication device according to the embodiment of the present invention;

FIGS. 3A to 3C show signals before and after encryption by rearrangement, respectively.

FIG. 4 is a flowchart showing an operation on the transmission side of the secret communication device.

FIG. 5 is a flowchart showing an operation on the receiving side of the secret communication device.

FIG. 6 shows a configuration diagram of a secret signal transmitting apparatus and a receiving apparatus according to another embodiment of the present invention.

FIG. 7 shows a configuration diagram of a conventional secret signal transmission / reception device.

Claims (14)

[Claims] An encrypted signal obtained by encrypting an original signal to be transmitted and a key signal for the encryption are respectively transmitted by different modulation methods, and these signals are separately received and demodulated. 2. A confidential communication method comprising: decrypting an encrypted signal by using the method to reproduce an original signal. 2. The confidential communication method according to claim 1, wherein the encryption is performed by rearranging the original signal, and the key signal is a signal representing the contents of the rearrangement. 3. The transmission frequency of one or both of an encrypted signal and a key signal is multiplexed.
Or the confidential communication method described in 2. 4. The method according to claim 1, wherein encryption is performed by changing a modulation factor at the time of transmission, and the key signal is a signal representing the change in the modulation factor. Secret communication method. 5. An encrypted signal transmitting unit for encrypting an original signal to be transmitted and transmitting the encrypted signal by a first modulation method, wherein the encrypted key signal is transmitted to a second signal. A secret signal transmission device comprising: a key signal transmission unit that transmits a signal by a modulation method. 6. The encrypted signal transmitting section rearranges an original signal to be transmitted to perform encryption, and the key signal transmitting section transmits the rearranged content as a key signal. The confidential signal transmitting device according to claim 5. 7. The secret signal transmitting apparatus according to claim 5, wherein one or both of the encrypted signal transmitting section and the key signal transmitting section have multiplexed transmission frequencies. 8. The encryption signal transmission section performs encryption by changing a modulation degree of the transmission section, and the key signal transmission section transmits a signal representing the change in the modulation degree as a key signal. The secret signal transmission device according to claim 5, wherein 9. An encrypted signal receiving section for receiving and demodulating an encrypted signal and a key signal, respectively, and an encrypted signal received by using the received key signal. A secret signal receiving device comprising: a decoding unit for decoding and reproducing an original signal. 10. When the encrypted signal is a signal obtained by rearranging the original signal, means for accumulating and storing the encrypted signal and the key signal until the reception amount of the encrypted signal and the key signal become a fixed amount are provided. The secret signal receiving apparatus according to claim 9, wherein the original signal is reproduced by synchronizing those signals. 11. A confidential signal transmitting apparatus according to claim 5 and claim 9.
And a confidential signal receiving device. 12. A confidential signal transmitting apparatus according to claim 6 and claim 1.
A confidential communication device comprising a confidential signal receiving device of 0. 13. The confidential communication device according to claim 11, wherein one or both of the encrypted signal transmitting unit and the key signal transmitting unit are multiplexed transmission frequencies. 14. The encryption signal transmission unit performs encryption by changing a modulation factor at the time of transmission, and the key signal transmission unit transmits a signal representing the change in the modulation factor as a key signal, The confidential communication device according to claim 11, wherein the reproducing unit decrypts an encrypted signal using the signal indicating the change in the modulation factor to reproduce an original signal.