JP2005110223A - Information transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems of a conventional system that a computing unit with a large scale circuit is required, much time is required for the calculations and the authentication time is extended because complicated (sophisticated) calculations are needed for transmission / reception of an encryption key and an authentication method or the like. <P>SOLUTION: A comparator 38 compares an initial vector produced by a receiver and outputted from a converter 37 with an initial vector obtained from a received signal as to whether or not the initial vectors have an identical value, and when the values of the initial vectors are identical to each other, it can be discriminated that the encryption key obtained after that is the same as that of a transmission apparatus. An initial vector outputted from a register 40 is fed to an encryption unit 41 as a first word, encrypted by using an encryption key from an encryption key storage device 39, part of an output of the encryption unit 41 is returned to the register 40 to form a publicly-known OFB mode for a succeeding word, and the output of the encryption unit 41 is fed to an adder 34 as an encryption key to decrypt the encrypted received signal from a synchronization detector 31. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an information transmission method, and more particularly to an information transmission method for transmitting arbitrary digital information while ensuring confidentiality to an arbitrary device.

  In the case of transmitting arbitrary digital information to an arbitrary device, transmission is generally performed in a signal format as shown in FIG. In the figure, a synchronization bit 1 for identifying the first bit of transmission information is added immediately before data 2 which is digital information transmitted every predetermined transmission signal unit, and a parity for detecting an error in data 2 3 is added after the data 2.

  However, when digital information (data) is transmitted in a predetermined transmission signal unit in such a signal format, anyone can wiretap the data 2 once the format is known. Therefore, in order to conceal the data 2 in order to ensure the confidentiality of the data 2, it is generally encrypted. When performing this encryption, DES (Data Encryption Standard) is the most frequently used cipher. Since DES is a block cipher, even if a 1-bit error occurs in the transmission path, for example, 64 bits in the entire block result in an error, resulting in a problem that the correction capability is significantly impaired.

  Therefore, the OFS (output feedback) mode of DES is used in an application where digital information is transmitted through a transmission path in which bit errors are likely to occur. In the OFB mode, the DES output is set as a pseudo random number by setting the DES output as the DES input of the next block, and the transmission information is concealed by taking the exclusive OR of the DES output and the transmission information. Yes (for example, see Non-Patent Document 1). In this way, when performing encryption and transmitting information, it is necessary to send / receive and share the encryption key. To send / receive and share the encryption key, an authentication method that requires complicated operations is used. It is common to do.

Okamoto Tatsuaki and Yamamoto Hiroshi, “Contemporary Cryptography”, first edition, Sangyo Tosho Co., Ltd., June 1997, p. 73-75

  However, the conventional information transmission method requires complicated (advanced) computation for encryption key transmission / reception and authentication, etc., so that a computation device with a large circuit scale is required or computation takes time. Inconveniences such as long authentication time. Furthermore, in order to improve confidentiality, it is common to update the encryption key frequently, and there is a disadvantage that an authentication method having a complicated calculation must be used each time. Further, in the DES-OFB mode, an operation for changing the scramble pattern is performed by changing the initial value. For this change of the initial value, it is necessary to use an authentication method that requires complicated calculation each time. There are also inconveniences.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide an information transmission method capable of updating an encryption key at a low cost and transmitting information by performing encryption with high concealment capability. And

In order to achieve the above-mentioned object, the present invention achieves the above-described object by the transmitting apparatus to encrypt the first synchronization signal and the second synchronization signal having a fixed period and transmitted in a plurality of periods within one period of the first synchronization signal. An information transmission method for transmitting information, detecting first and second synchronization signals in a received signal by a receiving device, and decrypting desired encrypted information,
Each of the transmission device and the reception device generates a pseudo random signal by the shift operation of the linear shift register synchronized with the second synchronization signal, and performs the shift operation of the linear shift register for a predetermined period in synchronization with the first synchronization signal. The first and second initial values using different one-way functions are generated separately based on the pseudo-random signal generating means that pauses and the pseudo-random signal generated by the pseudo-random signal generating means. And the second initial value generation means and the pseudo random signal generated by the pseudo random signal generation means in synchronization with the second synchronization signal, encryption keys having different values in synchronization with the second synchronization signal. And a key generation means for generating,
The transmitting apparatus encrypts desired information using the encryption key from the key generation means and the second initial value from the second initial value generation means, and converts the desired information encrypted into the first and second information. And generating a transmission signal obtained by synthesizing the first initial value with the output of the encryption means during a predetermined period during which the shift operation of the pseudo random signal generation means is suspended and the encryption means that is output together with the synchronization signal. The reception apparatus further includes a transmission signal generation means, and the reception device compares the received value of the first initial value in the received transmission signal with the first initial value generated by the first initial value generation means of itself. In the received transmission signal, the comparison means for checking the synchronization relationship between the transmission side and the reception side, the encryption key from the key generation means, and the second initial value from the second initial value generation means are used. And a decryption means for decrypting the encrypted desired information. Those were.

  In this invention, the transmission device and the reception device each generate the first and second initial values and the encryption key based on the pseudo random signal generated by the single pseudo random signal generation unit. The encrypted desired information generated by encrypting the desired information using the encryption key updated in synchronization with the synchronization signal and the second initial value is multiplexed with the first and second synchronization signals. In addition, the transmission signal formed by synthesizing the first initial value instead of the desired information is transmitted during a predetermined period in which the shift operation of the pseudo random signal generating means synchronized with the first synchronization signal is suspended. Without transmitting the encryption key and the second initial value, it is possible to transmit desired information frequently encrypted with a different encryption key in synchronization with the second synchronization signal. Further, in the receiving device, the first initial value in the received transmission signal is compared with the first initial value generated by the receiving device itself, thereby checking the synchronization relationship between the transmitting side and the receiving side, When it is confirmed that there is a synchronization relationship, in the received transmission signal using the encryption key and the second initial value generated by the receiver itself in synchronization with the second synchronizing signal in the received transmission signal. The encrypted desired information can be decrypted (decrypted).

  In order to achieve the above object, according to the present invention, the first synchronizing signal is a vertical synchronizing signal, the second synchronizing signal is a horizontal synchronizing signal, and the pseudo-random signal generating means The shift operation of the linear shift register is paused in the blanking area for a predetermined period, and the shift operation of the linear shift register is performed for each horizontal synchronization signal input in the data area period after the blanking area. The first initial value is generated at the time when the horizontal synchronizing signal is input in the blanking area, and the encrypting means and the second initial value generating means are provided for each horizontal synchronizing signal input in the data area period after the blanking area. The encryption key and the second initial value are updated in synchronization with the shift operation of the linear shift register of the pseudo-random signal generation means, and the encryption means encrypts desired information within the data area period. In encrypted decryption means it is characterized by decrypting the desired information encrypted in the data area period encryption key.

  In the present invention, the desired information that is encrypted and transmitted in the data area period in the transmitting device is encrypted based on the second initial value and the encryption key that are updated every time the horizontal synchronization signal is input, and the receiving device The first initial value in the blanking area in the received transmission signal is compared with the first initial value generated by the receiving device itself, and the encryption key generated by the receiving device itself in the data area period and Using the second initial value, the encrypted information can be decrypted.

  Further, in order to achieve the above object, according to the present invention, when the number of second synchronization signals transmitted within one cycle of the first synchronization signal is not a predetermined number, And a function of correcting so that the number of shift operations within one cycle of the first synchronization signal becomes a specified value within a predetermined period during which the shift operation of the linear shift register is suspended after the synchronization signal is input. And

  According to the present invention, in the transmission device, by transmitting a transmission signal obtained by synthesizing the first initial value during a predetermined period in which the shift operation of the pseudo random signal generating means synchronized with the first synchronization signal is suspended. Since the desired information frequently encrypted with the different encryption key is transmitted in synchronization with the second synchronization signal without transmitting the encryption key and the second initial value, the encryption key and the second Compared to the case where the initial value is synchronized with the second synchronization signal and transmitted each time, the encryption transmission is more efficient and the concealment capability is higher. Further, since the first initial value to be transmitted is a value generated using a one-way function, the value of the linear shift register, the second initial value, the cipher even if the first initial value is intercepted due to unauthorized reception. The key value is never inferred.

  Further, according to the present invention, each of the transmission device and the reception device can encrypt desired information based on a pseudo random signal generated by a single pseudo random signal generation unit, or can encrypt an encrypted desired signal in a received signal. Therefore, the transmitting apparatus having the encrypting means and the receiving apparatus having the decrypting means can be configured at low cost.

  Further, according to the present invention, the receiving device compares the received value of the first initial value in the received transmission signal with the first initial value generated by its own first initial value generating means. Since the synchronization relationship between the transmitting side and the receiving side is checked, a more reliable information transmission system operation can be realized.

  Furthermore, according to the present invention, the pseudo random signal generating means in the receiving device has a function of correcting the number of shift operations within one cycle of the first synchronization signal so as to become a specified value. Asynchrony between the transmission side and the reception side due to a detection error can be prevented.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a transmitting apparatus according to an embodiment of an information transmission system according to the present invention, FIG. 2 is a signal format diagram of an embodiment of a transmission signal transmitted by the information transmission system according to the present invention, and FIG. The block diagram of the receiver of one Embodiment of the information transmission system which becomes this invention is shown.

  First, the transmission apparatus will be described with reference to FIG. An input signal to be transmitted (a signal made up of stream data such as a horizontal synchronization signal, a vertical synchronization signal, a blanking signal, and video data) is supplied to the synchronization detector 11 to detect a horizontal synchronization signal and a vertical synchronization signal. . The detection signal output of the synchronization detector 11 is supplied to the M-sequence generator 12 and the 64-bit register 13, respectively. The input signal is supplied to an adder 14 which will be described later.

  Here, the M-sequence generator 12 is a random number generator (pseudo-random signal generating means) composed of a well-known linear shift register, and the block after the vertical synchronization signal detection signal is input from the synchronization detector 11. The shift operation is stopped in the ranking area, and after the blanking area, 1-bit shift is performed together with the 64-bit register 13 every time the horizontal synchronization signal detection signal is input. In the initial state, the M-sequence generator 12 is in a standby state in which it is transmitted in advance or is loaded with a predetermined initial value.

  The 64-bit register 13 holds the output signal of the M-sequence generator 12 and at the same time supplies the values held in the converters 15, 16 and 17, respectively. The converters 15, 16 and 17 are converters based on a one-way function, and convert the values supplied from the 64-bit register 13 into different values. The value obtained by conversion by the first converter 15 is temporarily stored in the encryption key storage 18 as a DES key.

  The value of the 64-bit register 13 output when the last horizontal synchronization signal detection signal in the blanking area is input is converted by the third converter 17 and then supplied as an initial vector to the combiner 21 described later. The Further, in the data area period in which the stream data after the blanking area is transmitted, 1-bit shift of the M-sequence generator 12 and the 64-bit register 13 is performed every time the horizontal synchronization signal is detected. The value output from the second converter 16 that converts the value is supplied to the register 19 as an initial vector.

  The register 19, the encryptor 20 and the adder 14 constitute a known OFB mode encryption circuit, and supplies the initial vector (initial value) output from the register 19 to the encryptor 20 as the first word. Then, encryption is performed using the encryption key from the encryption key storage unit 18, and the output of the encryption unit 20 is returned to the register 19 to form a known OFB mode as the next word, while the output of the encryption unit 20 is supplied to the adder 14. Supply.

  As a result, the signal from the synchronization detector 11 is subjected to an exclusive OR operation with the output signal of the encryptor 20 by the adder 14, thereby encrypting the portion excluding the horizontal / vertical synchronization signal and the blanking signal. It is taken out and supplied to the combiner 21 where it is combined with the initial vector in the blanking area from the converter 17 in time series.

  Note that the synchronization detector 11 detects the vertical synchronization signal to detect the beginning of the frame, and the shift operation of the M-sequence generator 12 is stopped in the blanking area following the vertical synchronization signal.

  In this way, a transmission signal having a signal format of one frame (or one field) as shown in FIG. 2 is extracted from the combiner 21 and transmitted to the information receiving apparatus. Here, in FIG. 2, V synchronization 23 indicates a vertical synchronization signal, and H synchronization 24 indicates a horizontal synchronization signal. Further, the initial vector 26 output from the converter 17 is synthesized in time series following the last horizontal synchronizing signal in the blanking area 25.

  Further, the stream data in the data area 27 is encrypted as described above, but for each horizontal synchronization signal section, the M-sequence generator 12 and the 64-bit register are used based on the leading horizontal synchronization signal (H synchronization). 13 is shifted by 1 bit, and the initial vector output from the converter 16 and input to the OFB mode encryption circuit and the encryption key output from the converter 15 are also changed. The value to be changed is also changed to another value for each horizontal sync signal interval.

  That is, according to the present embodiment, the stream data in the data area 27 is encrypted with a different encryption key for each horizontal synchronization signal section, and the initial vector 26 for synchronization detection is time-sequentially placed in the blanking area 25. The transmission signal that is synthesized is transmitted, and the initial value (first word) of the encryption key and the encryption key itself are not transmitted. It should be noted that the parity 28 in the transmission signal format shown in FIG. 2 is generated and added based on the signal of each horizontal synchronization signal section by an error check code generation circuit (not shown in FIG. 1).

  Next, the receiving apparatus will be described with reference to FIG. The receiving apparatus has substantially the same configuration as that of the transmitting apparatus in FIG. 1 except that a comparator 38 is added. In FIG. 3, the received signal having the signal format shown in FIG. 2 is supplied to the synchronization detector 31 to detect the vertical synchronization signal and the horizontal synchronization signal, and the detection signal output is the M-sequence generator 32 and 64 bits. While being supplied to each of the registers 33, the input signal is supplied to an adder 34 described later.

  Here, the M-sequence generator 32 has the same configuration as the M-sequence generator 12 on the transmission side, and stops the shift operation in the blanking area after the vertical synchronization signal detection signal is input from the synchronization detector 31. After the blanking area, a 1-bit shift is performed together with the 64-bit register 33 every time a horizontal synchronization signal detection signal is input. If a synchronization undetected error occurs in the data area, the prescribed number of shift operations of the M-sequence generator 12 are performed in the blanking area of the next frame, and the number of shifts in one frame is always the prescribed value. Correct so that That is, since the total number of shifts of the M-sequence generator 12 performed every time the horizontal synchronization signal is detected in one frame is a known specified value, if it is not this specified value, the shift is performed within the blanking area and Adjust so that

  The 64-bit register 33 holds the output signal of the M-sequence generator 32 and simultaneously supplies the values to the converters 35, 36 and 37, respectively. The converters 35, 36 and 37 are converters based on a one-way function, and convert the values supplied from the 64-bit register 33 into different values.

  However, the converters 35, 36, and 37 have the same configuration as the corresponding converters 15, 16, and 17 on the transmission side, and the output conversion values of the converter 35 and the converter 15 have the same value with respect to the same input value. Similarly, the conversion values are output, and the output conversion values of the converter 36 and the converter 16 and the output conversion values of the converter 37 and the converter 17 output the same conversion value for the same input value. The value obtained by the conversion by the first converter 35 is temporarily stored in the encryption key storage 39 as a DES key.

  Here, the value of the 64-bit register 33 output when the last horizontal synchronizing signal detection signal in the blanking area is input is converted by the third converter 37 and generated as an initial vector. The generator 32 has the same configuration as that of the M-sequence generator 12 on the transmission side, and when there is no transmission error, the value of this initial vector is the reception of the signal format shown in FIG. It becomes the same value as the initial vector 26 in the signal.

  Therefore, in the present embodiment, the comparator 38 determines whether or not the initial vector generated by the receiving device output from the converter 37 is the same value as the initial vector 26 obtained from the received signal. If compared, if it is the same, it can be determined that the encryption key (decryption key) obtained thereafter is the same as that of the transmitting device, so the operation described below is continued, but when different, the encryption key (decryption key) is Since it can be determined that it is not the same as that of the transmitting apparatus, a signal indicating that is transmitted to the transmitting apparatus, and the M-sequence generator 32 is initially reset. The M-sequence generator 12 in the transmission device is also initially reset by the transmission signal.

  When the same comparison result is obtained by the comparator 38, in the data area period in which the stream data after the blanking area of the received signal is transmitted, the M sequence generator 32 The 64-bit register 33 is shifted by 1 bit, and the value output from the second converter 36 that converts the output value of the 64-bit register 33 at that time is supplied to the register 40 as an initial vector.

  The register 40, the encryptor 41, and the adder 34 constitute a known OFB mode encryption circuit, and supplies the initial vector (initial value) output from the register 40 to the encryptor 41 as the first word. The encryption key is encrypted using the encryption key from the encryption key storage device 39, and the output of the encryption device 41 is returned to the register 40 to form a known OFB mode as the next word, while the output signal of the encryption device 41 is added to the adder 34. To supply.

  Here, in the present embodiment, the transmitting device and the receiving device generate initial vectors in synchronization with each other, and therefore the OFB mode encryption circuit and decryption circuit are the transmission device and the reception device, respectively, as shown in FIGS. As shown in FIG. As a result, the received signal from the synchronization detector 31 is subjected to an exclusive OR operation with the same encryption key as that of the transmission side by the adder 34, and is decrypted (decrypted) and taken out. The decrypted stream data and parity extracted from the adder 34 are supplied to the error detector 42, where an error check is performed based on the parity, and output.

  As described above, according to the present embodiment, the initial vector is transmitted for each frame (or field) period, and the initial vector generated for each frame (or field) on the receiving side is compared with the received initial vector to match. By checking that the encryption key generated on the transmission side and the encryption key generated on the reception side are the same for each frame (or field), In the data area, the initial value (first word) and encryption key of the encryption circuit are generated on the receiving side by the converters 36 and 35 for each horizontal synchronizing signal section, and the same values as those on the transmitting side are generated for each horizontal synchronizing signal section. Data streams encrypted with different encryption keys can be decrypted.

  When a synchronization undetected error occurs in the data area, the M-sequence generator 32 performs a specified number of shift operations in the blanking area of the received signal that is not originally shifted by the M-sequence generator 32. The correction is always performed so that the number of shifts in one frame becomes a specified value. This prevents asynchronization between the transmission side and the reception side due to a synchronization non-detection error.

  Therefore, according to the present embodiment, it is possible to provide an encryption method with high concealment capability by frequently changing the initial value (first word) of the encryption key and the encryption circuit to a different value for each horizontal synchronization signal section, In addition, since the encryption key and the initial value (first word) of the encryption circuit are not transmitted and are generated synchronously on the transmission side and the reception side, the efficiency of transmitting them is low. It is possible to prevent the attacker from giving the information of the encryption attack, and by checking the synchronization relationship between the transmission side and the reception side, an efficient and inexpensive encryption method can be provided.

  Next, the best mode for carrying out the second invention will be described with reference to the drawings. FIG. 4 is a block diagram of a transmitting apparatus according to another embodiment of the information transmission method according to the present invention. FIG. 5 is a signal format diagram of another embodiment of a transmission signal transmitted by the information transmission method according to the present invention. 6 shows a block diagram of a receiving apparatus according to another embodiment of the information transmission system according to the present invention. In each figure, the same components as those in FIG. 1, FIG. 2, or FIG.

  First, the transmission apparatus will be described with reference to FIG. The operations other than the synchronization detector 45, the encryption key storage 46, the encryption key storage 47, and the encryption key selector 48 are the same as the operations of the transmission apparatus shown in FIG. In FIG. 4, an input signal to be transmitted is a signal composed of stream data such as a horizontal synchronization signal, a vertical synchronization signal, a blanking signal, and video data. In this embodiment, the synchronization signal of the input signal is Unlike the above-described embodiment, the vertical synchronization signal has one pattern as in the above embodiment, whereas the horizontal synchronization signal has two patterns (horizontal synchronization signal A and horizontal synchronization signal B).

  When the synchronization detector 45 detects the horizontal synchronization signal A from the input signal, the encryption key selector 48 to which the detection signal is supplied selects the encryption key of the encryption key storage 46 and supplies it to the encryptor 20 for encryption. The unit 20 generates a cipher stream in a known OFB mode and supplies the output to the adder 14. As a result, the signal from the synchronization detector 45 is subjected to an exclusive OR operation with the output signal of the encryptor 20 by the adder 14, thereby encrypting the portion excluding the horizontal / vertical synchronization signal and the blanking signal. It is taken out and supplied to the combiner 21 where it is combined with the initial vector in the blanking area from the converter 17 in time series.

  Similarly, when the synchronization detector 45 detects the horizontal synchronization signal B from the input signal, the encryption key selector 48 to which the detection signal is supplied selects the encryption key in the encryption key storage 47 and supplies it to the encryptor 20. Then, the encryptor 20 generates an encrypted stream in a known OFB mode and supplies the output to the adder 14. As a result, the signal from the synchronization detector 45 is subjected to an exclusive OR operation with the output signal of the encryptor 20 by the adder 14, thereby encrypting the portion excluding the horizontal / vertical synchronization signal and the blanking signal. It is taken out and supplied to the combiner 21 where it is combined with the initial vector in the blanking area from the converter 17 in time series.

  Further, when detecting the vertical synchronization signal, the synchronization detector 45 outputs a storage command to the encryption key storage 46 or the encryption key storage 47 and stores the output value of the converter 15 at that time. When the encryption key selector 48 selects the encryption key of the encryption key storage 46, the encryption key storage 47 is encrypted. When the encryption key selector 48 selects the encryption key of the encryption key storage 47, the encryption key is stored. The key memory 46 stores the new value.

  Thus, by selecting the arrangement of the horizontal synchronization signal A and the horizontal synchronization signal B of the input signal, the encryption key switching point can be freely set. An example of the arrangement of the horizontal synchronizing signal A and the horizontal synchronizing signal B of the input signal is shown in FIG. In the figure, the same parts as those in FIG. In FIG. 5, H synchronization A 51 indicates horizontal synchronization signal A, H synchronization B 52 indicates horizontal synchronization signal B, and data area 53 is provided in an area following horizontal synchronization signal A or B other than blanking area 25. In the blanking area 25, as in the above embodiment, the value of the 64-bit register 13 is not updated, and the video signal is not encrypted.

  In this embodiment, at the time when the synchronization detector 45 detects the vertical synchronization signal, the encryption key from the converter 15 is written in which of the two encryption key storage units 46 and 47. , Since the encryption key selector 48 at that time is written in the non-selected storage device of the two encryption key storage devices 46 and 47, the encryption key storage devices 46 and 47 alternately The encryption key is not always written. Further, since the horizontal synchronization signal pattern (horizontal synchronization signal A, horizontal synchronization signal B) also changes irregularly, the obtained encryption key changes irregularly.

  Next, the receiving apparatus will be described with reference to FIG. In the figure, the same components as in FIG. In FIG. 6, operations other than the synchronization detector 55, the encryption key storage 56, the encryption key storage 57, and the encryption key selector 58 are the same as the operations of the receiving apparatus shown in FIG.

  In FIG. 6, the received signal is supplied to the synchronization detector 55 in the same manner as the transmitting device, and the horizontal synchronization signal A, the horizontal synchronization signal B, and the vertical synchronization signal are detected. When the horizontal synchronization signal A is detected, the encryption key selector 58 selects the encryption key of the encryption key storage 56 and supplies it to the encryption device 41. The encryption device 41 receives the encryption stream in a known OFB mode. And the output is supplied to the adder 34. As a result, the signal from the synchronization detector 55 is subjected to an exclusive OR operation with the output signal of the encryptor 41 by the adder 34, so that the portion excluding the horizontal / vertical sync signal and the blanking signal is decrypted. The data is taken out and supplied to the error detector 42. The error is checked based on the parity and output.

  Similarly, when the horizontal synchronization signal A is detected by the synchronization detector 55, the encryption key selector 58 selects the encryption key of the encryption key storage 57 and supplies it to the encryption device 41. The encryption device 41 An encrypted stream is generated in a known OFB mode, and the output is supplied to the adder 34. As a result, the signal from the synchronization detector 55 is subjected to an exclusive OR operation with the output signal of the encryptor 41 by the adder 34, and the portion excluding the horizontal / vertical synchronization signal and the blanking signal is decrypted. The data is taken out and supplied to the error detector 42. The error is checked based on the parity and output.

  When the synchronization detector 55 detects the vertical synchronization signal, it outputs a storage command to the encryption key storage 56 or the encryption key storage 57, and stores the output value of the converter 35 at that time. When the encryption key selector 58 selects the encryption key of the encryption key storage device 56, the encryption key storage device 57 selects the encryption key. When the encryption key selector 58 selects the encryption key of the encryption key storage device 57, encryption is performed. The key memory 56 stores the new value. Thus, the encryption of the data in the data area 53 is decrypted based on the horizontal synchronization signal A and the horizontal synchronization signal B which are freely arranged as in the format of FIG.

  According to the present embodiment, by properly setting the switching timing of two horizontal synchronization signal patterns (horizontal synchronization signal A and horizontal synchronization signal B), the sequence decoding of the M-sequence generator 12 shown in FIG. Can be difficult.

  In the above embodiment, the encryption circuit and the decryption circuit employ the DES OFB mode. However, the present invention is not limited to this, and other encryption schemes can be used even in a normal DES. But it is applicable to all ciphers that use initial values.

  In the above embodiment, the encryption key and the initial value of the encryption circuit are updated synchronously. However, the present invention is not limited to this, and the encryption key has an encryption key storage unit. Therefore, it goes without saying that, for example, the initial value of the encryption circuit is updated by the incoming of the vertical synchronizing signal, and the initial value of the encryption circuit is updated by the incoming of the horizontal synchronizing signal.

  In the above embodiment, the information transmitting / receiving apparatus has been described. However, the present invention is not limited to this, and can be used for a recording / reproducing apparatus. In the recording / reproducing apparatus, even if the information is output without being decrypted in the reproducing apparatus, since there is no encryption key switching information in the output stream, it is more difficult to decrypt even if the information is reproduced by an unauthorized reproducing apparatus. A safe information recording apparatus can be provided.

It is a block diagram of a transmitting apparatus according to an embodiment of the present invention. It is a signal format figure of one Embodiment of the transmission signal transmitted with this invention system. It is a block diagram of the receiver of one embodiment of the system of the present invention. It is a block diagram of the transmission apparatus of other embodiment of this invention system. It is a signal format figure of other embodiment of the transmission signal transmitted by this invention system. It is a block diagram of the receiver of other embodiment of this invention system. It is a signal format figure of an example of the transmission signal transmitted with a conventional system.

Explanation of symbols

11, 31, 45, 55 Sync detector 12, 32 M-sequence generator 13, 33 64-bit register 14, 34 Adder 15, 16, 17, 35, 36, 37 Converter 18, 39, 46, 47, 56 57 Encryption key storage 19, 40 Register 20, 41 Encryption 21 Synthesizer 23 Vertical synchronization signal (V synchronization)
24 Horizontal sync signal (H sync)
25 Blanking area 26 Initial vector 27 Data area 38 Comparator 48, 58 Encryption key selector

Claims (3)

The transmitting device transmits the desired information encrypted together with the first synchronizing signal and the second synchronizing signal having a fixed period transmitted within one cycle of the first synchronizing signal, and the receiving device receives the received signal. An information transmission method for detecting the first and second synchronization signals in the medium and decrypting the encrypted desired information,
The transmitting device and the receiving device each generate a pseudo-random signal by a shift operation of a linear shift register synchronized with the second synchronization signal, and perform the linear shift for a predetermined period in synchronization with the first synchronization signal. A pseudo-random signal generating means for pausing the shift operation of the register;
First and second initial value generating means for separately generating the first and second initial values based on the pseudo random signal generated by the pseudo random signal generating means;
Key generation means for generating encryption keys having different values in synchronization with the second synchronization signal based on the pseudo random signal generated in synchronization with the second synchronization signal by the pseudo random signal generation means; And having
The transmitting apparatus encrypts the desired information by using the encryption key from the key generation unit and the second initial value from the second initial value generation unit, and the encrypted desired information. Encryption means for outputting together with the first and second synchronization signals;
Transmission signal generating means for generating and transmitting a transmission signal obtained by synthesizing the first initial value with the output of the encryption means during the predetermined period during which the shift operation of the pseudo random signal generation means is suspended; In addition,
The receiving device compares the received value of the first initial value in the received transmission signal with the first initial value generated by the first initial value generating means of its own, And comparison means for checking the synchronization relationship between the receiver and the receiver,
Decryption for decrypting the encrypted desired information in the received transmission signal using the encryption key from the key generation means and the second initial value from the second initial value generation means And an information transmission method.   The first synchronizing signal is a vertical synchronizing signal, the second synchronizing signal is a horizontal synchronizing signal, and the pseudo-random signal generating means is configured so that the blanking area in the predetermined period after the vertical synchronizing signal is input The shift operation of the linear shift register is paused, the shift operation of the linear shift register is performed every time the horizontal synchronization signal is input in the data area period after the blanking area, and the first initial value generating means includes the blanking The first initial value is generated at the time of input of the horizontal synchronization signal in the area, and the encryption means and the second initial value generation means are configured to generate the horizontal synchronization within the data area period after the blanking area. Each time a signal is input, the encryption key and the second initial value are updated in synchronization with the shift operation of the linear shift register of the pseudo random signal generation means, The encryption means encrypts the desired information with the encryption key within the data area period, and the decryption means decrypts the encrypted desired information with the encryption key within the data area period. The information transmission system according to claim 1, wherein: The pseudo-random signal generating means in the receiving device is configured to receive a signal after the first synchronization signal is input when the number of the second synchronization signals transmitted within one period of the first synchronization signal is not a predetermined number. And a function of correcting the number of shift operations within one cycle of the first synchronization signal within a predetermined period during which the shift operation of the linear shift register is suspended. Item 1. The information transmission method according to item 1 or 2.

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