JP4729888B2 - Information transmission method, transmitter and receiver - Google Patents

Description

  The present invention relates to an information transmission method, a transmission device, and a reception device, and more particularly, to an information transmission method, a transmission device, and a reception device that transmit 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 (see Non-Patent Document 1, for example). 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, an information transmission method, a transmission apparatus, and a reception apparatus that can update an encryption key at low cost and can transmit information by performing encryption with high concealment capability. The purpose is to provide.

  Another object of the present invention is to delete the encryption key switching information from the stream information and add an additional bit, which conventionally required to transmit the switching information together with the encryption information when frequently updating the encryption key. It is an object of the present invention to provide an information transmission method, a transmission device, and a reception device that can efficiently transmit encryption key switching information without using the device.

In order to achieve the above object, an information transmission system according to a first aspect of the present invention provides desired information together with a vertical synchronization signal and a horizontal synchronization signal of the first and second patterns transmitted by a transmission device at a predetermined interval. encrypt and send, to detect a vertical synchronizing signal and a horizontal synchronizing signal in the received signal by the receiving device, an information transmission method to decrypt the desired information is encrypted,
Transmission equipment generates a first detection means and the first pseudo random signal in accordance with the detected horizontal synchronizing signal by the first detection means for detecting a vertical synchronizing signal and a horizontal synchronizing signal from the incoming signal A first pseudo-random signal generating means that generates a different encryption key for each horizontal synchronization signal section based on the first pseudo-random signal, and each time the first detection means detects a vertical synchronization signal, The encryption key is written in either the storage device or the second storage device, and depending on whether the first detection means detects the horizontal synchronization signal of the first pattern or the horizontal synchronization signal of the second pattern, The encryption key stored in the first storage device and the encryption key stored in the second storage device are selected, the desired information is encrypted using the selected encryption key, and the encrypted desired to send information along with vertical and horizontal synchronization signals And an encryption unit,
Receiving device generates a second pseudo random signal in response to the second detection means and the detected horizontal synchronizing signal by the second detection means for detecting a vertical synchronizing signal and a horizontal synchronizing signal from the received signal A different pseudo key is generated for each horizontal synchronizing signal section based on the second pseudo random signal generating means and the second pseudo random signal, and the first memory is detected each time the first detecting means detects the vertical synchronizing signal. Depending on whether the first detection means detects the horizontal sync signal of the first pattern or the horizontal sync signal of the second pattern. 1 select a storage encryption key stored in the device and the encryption key stored in the second storage device, the desired information is encrypted in the received signal in the selected encryption key to decrypt decryption And a means for generating data.

  The present invention is characterized in that the transmitting apparatus transmits desired information frequently encrypted with a different encryption key in synchronization with the synchronization signal without transmitting the encryption key and the initial value. In the present invention, since different encryption keys are used according to the type of the synchronization signal, the encryption key can be switched by switching the type of the synchronization signal at any time without additional information.

In order to achieve the above object, the transmission device of the second invention encrypts desired information together with a vertical synchronization signal transmitted in a plurality at predetermined intervals and horizontal synchronization signals of the first and second patterns. A transmission apparatus for transmitting, wherein a detection means for detecting a vertical synchronization signal and a horizontal synchronization signal from an incoming signal, and a pseudo random signal by a shift operation of a linear shift register synchronized with the horizontal synchronization signal detected by the detection means And a pseudo random signal generating means for generating a different encryption key for each horizontal synchronization signal section based on the pseudo random signal, and a first storage and a second storage each time the detection means detects a vertical synchronization signal. An encryption key is written in one of the storage devices and stored in the first storage device depending on whether the detection means detects the horizontal synchronization signal of the first pattern or the horizontal synchronization signal of the second pattern. Select the an encryption key and encryption key stored in the second storage device, it encrypts the desired information using the selected encryption key, encrypted desired information vertical sync signal and has And encryption means for sending out together with the horizontal synchronizing signal .

In order to achieve the above object, the transmitting apparatus of the third invention further includes an initial value generating means for generating an initial value based on a pseudo random signal generated by the pseudo random signal generating means, and the encrypting means includes: Encryption of desired information is started using an initial value that is generated by an initial value generating means and changes every time a linear shift register performs a shift operation.

In order to achieve the above object, a receiving device according to a fourth aspect of the invention includes a vertical synchronizing signal transmitted by a transmitting device and transmitted in a plurality at predetermined intervals, and horizontal synchronizing signals of first and second patterns , Receives a multiplexed signal composed of desired information encrypted with different encryption keys according to the horizontal synchronization signal pattern , detects the vertical synchronization signal and the horizontal synchronization signal from the received signal, and encrypts the desired information A detecting device for detecting a vertical synchronizing signal and a horizontal synchronizing signal from a received signal, and a pseudo random signal by a shift operation of a linear shift register synchronized with the horizontal synchronizing signal detected by the detecting device a pseudo random signal generating means for generating, to generate different encryption keys for each horizontal synchronizing signal period on the basis of a pseudo-random signal, first each time the detecting means detects a vertical synchronization signal The encryption key is written in either the storage device or the second storage device, and the detection means detects whether the first pattern horizontal synchronization signal or the second pattern horizontal synchronization signal is detected. And a decryption unit that selects an encryption key stored in the storage device and an encryption key stored in the second storage device, and decrypts desired information using the selected encryption key. To do.

In order to achieve the above object, the receiving apparatus according to the fifth aspect of the present invention further comprises an initial value generating means for generating an initial value based on a pseudo random signal generated by the pseudo random signal generating means, and the decoding means comprises: Decryption of desired information is started using an initial value generated by an initial value generating means and changing every time a linear shift register performs a shift operation.

  According to the present invention, the encryption key is switched by switching the type of the synchronization signal at any time without additional information by using different encryption keys according to the type of the synchronization signal. High information transmission can be realized.

  Further, according to the present invention, the sequence decoding of the pseudo random signal can be made more difficult by appropriately setting the switching timing of the type of the synchronization signal.

  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 B 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 (5)

The transmission device encrypts and transmits the desired information together with the vertical synchronization signal transmitted in a plurality of intervals at predetermined intervals and the horizontal synchronization signals of the first and second patterns, and the reception device transmits the vertical synchronization signal in the reception signal and wherein detecting a horizontal synchronizing signal, an information transmission method for decrypting said desired information is encrypted,
The transmitter is
First detecting means for detecting the vertical synchronizing signal and the horizontal synchronizing signal from an incoming signal;
First pseudo random signal generation means for generating a first pseudo random signal in response to the horizontal synchronization signal detected by the first detection means;
A different encryption key is generated for each of the horizontal synchronization signal sections based on the first pseudo-random signal, and each time the first detection means detects the vertical synchronization signal, a first memory and a second memory are generated. An encryption key is written in any of the first and second detectors, and the first detecting means detects the first pattern horizontal synchronizing signal or the second pattern horizontal synchronizing signal. select stored in the storage unit cryptographic key and a cryptographic key stored in the second storage device, encrypts the desired information using the selected encryption key, the desired encrypted Encryption means for sending information together with the vertical synchronization signal and the horizontal synchronization signal ;
The receiving device is:
Second detection means for detecting the vertical synchronization signal and the horizontal synchronization signal from the received signal;
Second pseudo random signal generating means for generating a second pseudo random signal in response to the horizontal synchronization signal detected by the second detection means;
A different encryption key is generated for each of the horizontal synchronization signal sections based on the second pseudo-random signal, and each time the first detection means detects the vertical synchronization signal, a first memory and a second memory are generated. An encryption key is written in any of the first and second detectors, and the first detecting means detects the first pattern horizontal synchronizing signal or the second pattern horizontal synchronizing signal. select stored in the storage unit cryptographic key and a cryptographic key stored in the second storage unit, the encrypted said desired information is in said received signal in the selected encryption key to decrypt An information transmission system characterized by comprising a decoding means. A transmission device that encrypts and transmits desired information together with a vertical synchronization signal transmitted in a plurality at a predetermined interval and horizontal synchronization signals of first and second patterns ,
Detecting means for detecting the vertical synchronizing signal and the horizontal synchronizing signal from incoming signals;
A pseudo-random signal generating means for generating a pseudo-random signal by a shift operation of a linear shift register synchronized with the horizontal synchronizing signal detected by the detecting means;
A different encryption key is generated for each horizontal synchronization signal section based on the pseudo-random signal, and each time the detection unit detects the vertical synchronization signal, the encryption key is set to one of the first storage device and the second storage device. An encryption key is written, and depending on whether the detection means detects the horizontal synchronization signal of the first pattern or the horizontal synchronization signal of the second pattern, the encryption key stored in the first storage device and It said second selecting an encryption key stored in the storage device, encrypts the desired information using the selected encryption key, the vertical synchronizing signal and the said desired information is encrypted And an encryption means for sending out together with the horizontal synchronizing signal . An initial value generating means for generating an initial value based on the pseudo random signal generated by the pseudo random signal generating means;
The encryption means starts encryption of the desired information using the initial value generated by the initial value generation means, and the value is changed for each shift operation of the linear shift register. The transmission device according to claim 2 . A plurality of vertical synchronization signals transmitted by the transmission apparatus and transmitted at predetermined intervals, horizontal synchronization signals of the first and second patterns, and a desired encryption key encrypted according to a pattern of the horizontal synchronization signal. receiving a multiplexed signal composed of information, detects the vertical synchronization signal and the horizontal synchronizing signal from the received signal, the desired information encrypted a receiver for decryption,
Detecting means for detecting the vertical synchronizing signal and the horizontal synchronizing signal from the received signal;
A pseudo-random signal generating means for generating a pseudo-random signal by a shift operation of a linear shift register synchronized with the horizontal synchronizing signal detected by the detecting means;
A different encryption key is generated for each horizontal synchronization signal section based on the pseudo-random signal, and each time the detection unit detects the vertical synchronization signal, the encryption key is set to one of the first storage device and the second storage device. An encryption key is written, and depending on whether the detection means detects the horizontal synchronization signal of the first pattern or the horizontal synchronization signal of the second pattern, the encryption key stored in the first storage device and A receiving apparatus comprising: decryption means for selecting an encryption key stored in the second storage device and decrypting the desired information using the selected encryption key. An initial value generating means for generating an initial value based on the pseudo random signal generated by the pseudo random signal generating means;
The decrypting means starts decrypting the desired information using the initial value generated by the initial value generating means and changing every time a shift operation of the linear shift register is performed. The receiving device according to claim 4 .

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