JPH0437611B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an encryption/decryption device having a function of obtaining a key for decrypting encrypted digital data from digital data sent from a transmitting side.

When a broadcast program is memorized and broadcast, key distribution is required. Conventionally, two key delivery methods have been considered. One method is to allocate a master key to each terminal and encrypt the key to be distributed using the master key. This method has the disadvantage that as the number of receiving terminals increases, the amount of transmission by the broadcast station increases. Another method is to install a remote switch on the receiver that cannot be accessed even by the owner of the receiver, and for the broadcasting station to control the remote switch using broadcasting means. This method requires less transmission than the previous method, but it also allows you to store previously received signals and input them into the receiver later, or when a broadcast station sends a signal to turn off a remote switch. The disadvantage is that it is weak against the method of turning off the power to the receiver.

The object of the present invention is to provide an encryption/decryption device that eliminates the above-mentioned drawbacks.

The above objective can be achieved with an encryption/decryption device having the following configuration. That is, according to the first aspect of the present invention, in an encryption/decryption device having a function of obtaining a key for decoding encrypted digital data from digital data sent from a transmitting side, a key input to an input terminal is used. pattern determining means for receiving a digital pattern and determining whether or not the digital pattern belongs to a predetermined pattern group; code conversion means for converting the code of digital data inputted to the input terminal; and switch means for sending the output of the code conversion means to an output terminal or to an extraction means described later depending on the determination result of the pattern determination means. ,
extracting means that extracts a part of the output or extracts nothing depending on the output of the switching means; the pattern determining means, the code converting means, and the extracting means through channels other than the input terminal and the output terminal; The present invention is constructed as an encryption/decryption device characterized by comprising a protection means for preventing access to the switch means. Further, according to the second aspect of the present invention, in an encryption/decryption device having a function of obtaining a key for decrypting encrypted digital data from digital data sent from a transmitting side, the digital data input to the input terminal is - pattern determining means for receiving a pattern and determining whether or not the digital pattern belongs to a predetermined group of patterns, and converting the code of the digital pattern depending on the determination result of the pattern determining means; a first code conversion means for extracting a portion of the output or not extracting any of the output depending on the output of the first code conversion means; a second code conversion means for converting the code of digital data input to the input terminal; the pattern determination means, the first code conversion means, and the second code conversion through a circuit other than the input terminal and the output terminal; and a protection means for preventing access to the extraction means.

Hereinafter, the present invention will be explained in detail using block diagrams showing embodiments. FIG. 1 is a block diagram showing an embodiment of the first invention. Input terminal 101
Digital data for key distribution and digital data for information transmission are input to . The pattern determiner 102 outputs 1 if a predetermined pattern exists in the digital data input to the input terminal 101, and otherwise outputs 0. Let this predetermined pattern be P. The decoder 103 decodes the digital data input to the input terminal 101 using a digital pattern from the selector 108 described later as a key. A switch 104 sends the output of the decoder 103 to an extractor 105 (described later) if the output of the pattern determiner 102 is 1, and outputs it to an output terminal 109 if it is 0. The extractor 105 outputs a portion of the digital pattern from the switch 104 if a 1 is present in a predetermined position, and does not output if it is a 0. A first memory 106 is one of the extractors.
05, and a second memory 107 stores a predetermined digital pattern MK. If the output of the pattern determiner 102 is 1, the selector 108 outputs the digital pattern stored in the second memory, and if the output is 0, it outputs the digital pattern stored in the first memory. The protection device 110 connects the input terminal 101
and the pattern determiner 102, the decoder 103, the switch 104, the extractor 105, the first memory 106, the second memory 107, and the selector 108 can be accessed only through the output terminal 109. It is for.

FIG. 2 is a block diagram showing an embodiment of the second invention. The pattern determiner 202 has an input terminal 201
If a predetermined pattern P exists in the digital data input to the , it outputs 1, and if it does not exist, it outputs 0. Code converter 2
03 converts the code of the digital data input to the input terminal 201 if the output of the pattern determiner 202 is 1. The extractor 204 detects when a 1 is present in a predetermined position of the digital pattern from the transcoder 203;
A portion of the digital pattern is output. A decoder 205 decodes the digital data input to the input terminal 201 using the output of the extractor 204 as a key, and outputs the decoded data to an output terminal 206. The protection device 207 is for making it possible to access the pattern determiner 202, the code converter 203, the extractor 204, and the decoder 205 only through the input terminal 201 and the output terminal 206.

The operating principle of the first invention will be explained using the block diagram of the embodiment shown in FIG. The sending side encrypts digital data for key distribution using a predetermined key MK and sends it. Decoder 10
3 is a decoder for the cipher. FIG. 3 shows an example of the frame structure of the digital pattern for key distribution.
In the figure, pattern P is a predetermined pattern, and it is determined from this that it is digital data for key distribution. on/off/
The pattern is a pattern that indicates whether each receiver is qualified to receive a broadcast program.An address is specified for each receiver in advance, and according to the address, if it is qualified to receive it, it will be set to 1, and if it is not, it will be set to 1. If not, arrange the 0s in an on-off pattern. Key K is the key to be delivered. The key is not for delivery.Ordinary data is encrypted with the previously delivered key and sent. The principle of key distribution will be explained below with reference to FIG. Second memory 107
stores the key MK. Assume that the sending side sends digital data for key distribution. At this time, on the receiving side, the pattern determiner 102 detects pattern P and outputs 1. Since the output of the pattern determiner 102 is 1, the selector 108 outputs the content MK of the second memory 107. Decoder 103
uses the output MK of the selector 108 to restore the on/off pattern of the digital data for key distribution and the key K. Since the output of the pattern determiner 102 is 1, the switch 104 sends the output of the decoder 103 to the extractor 105 and does not output it to the output terminal 109. The extractor 105 stores the key K in the first memory 106 only when the bit at the position corresponding to the address of the receiver in the on-off pattern is 1, and does not store it when it is 0. When the transmitting side encrypts data that is not for key distribution with the key K and transmits it, the pattern determiner 102 outputs 0 on the receiving side. At this time, since the output of the pattern determiner 102 is 0, the selector 108 outputs the content K of the first memory 106. The decoder 103 decodes the data using K. Since the output of the pattern determiner 102 is 0, the switch 104 is activated by the decoder 10.
3 is output to the output terminal 109. The protection device 110 prevents anyone on the receiving side from knowing the MK and K, so the data cannot be decoded unless the bit at the position corresponding to the address of the receiver in the on-off pattern is 1. That is,
This bit acts as a remote switch from the sending side. If the key is changed to a new key K', it becomes useless for the receiving side to input the previous digital data for key distribution into the receiver, or to turn off the power to the receiver when transmitting the digital data for key distribution. This is because subsequent broadcast programs will be encrypted with K' and sent. Since the on/off pattern is only assigned one bit to one receiver, this method is more convenient for key distribution than the method of determining a master key for each receiver and encrypting the key K with the master key and sending it. Less digital data is required.

In the embodiment shown in FIG. 2, code converter 203 performs the operation of decoding the key distribution digital data with pattern MK, and decoder 205 performs the operation of decoding the data with key K. Similar to the embodiment of the first invention, the digital key distribution
Upon receiving the data, the code converter 203 restores the on/off pattern and the key K, and the extractor 204 outputs the key K if the bit in the on/off pattern corresponding to the address of the receiver is 1; If it is 0, it will not be output. The decoder 205 decodes the digital data input to the input terminal 201 using the key K. The protection device 207 functions similarly to the protection device 110 of the first invention. Therefore, the bits in the on-off pattern corresponding to the address of the protection device 207 and the receiver concerned are remote
An explanation of how the switch works will be omitted. Also, the pointlessness of re-entering previous key delivery digital data or turning off the receiver while key delivery digital data is being sent;
The reason why the key distribution digital data is shorter than before is the same as the first invention, so the explanation will be omitted.

FIG. 4 is a block diagram illustrating one embodiment of pattern determiners 102 and 202. In the figure,
Shift register 401 sequentially stores input digital data. The memory 403 stores the pattern P. An exclusive OR element 402 performs exclusive OR on each bit of the contents of the shift register 401 and the memory 403, and when the result is 0, the converter 404 outputs 1, and when the result is other than 0, it outputs 0. Output.

Decoders 103, 205 and code converter 203
To do this, a decryptor is used to decrypt the data sent by the sender after encrypting the key distribution digital data and other data.

The extractors 105, 204 can be configured with memory. That is, a key distribution digital pattern is stored, and from the on/off pattern therein, the bit at the position corresponding to the address of the receiver is 1.
When , the key part should be read, and when it is 0, it should not be read.

For example, the protective devices 110 and 207 may be sealed except for the input terminals and output terminals, and covered with a material that will destroy the contents if destroyed.

That is, the protection devices 110 and 207 are connected to the circuits (102 to 108 in FIG. 1, 202 to 2 in FIG.
05) is a box that is completely covered with a metal plate and the seams are welded without using screws, and the above memory is used as a battery backup random access memory, so that if the box is broken, the current from the battery to the memory is cut off. configured so that To do this, tighten a thread between two or more places on the inside of the metal plate and the battery.
A method is used in which when the metal plate is broken, the threads pull on the battery and come off.

In the above embodiment, the outputs of the pattern determiners 102 and 202 were set to 1.0, but the outputs may be other than 1.0 as long as they are two distinguishable symbols. Further, the frame structure is not limited to the structure shown in FIG. 3, but may be a different structure as long as it is determined in advance by the transmitting side and the receiving side. The on/off pattern can also be modified to align pairs of receiver addresses and bits indicating reception eligibility. Further, in the embodiment of the second invention,
If the transmitting side encrypts the digital data for key distribution and other data differently, the receiving side uses a decoder for the former encryption as the code converter 203,
By using the latter encryption decoder as the decoder 205, data can be decrypted. Furthermore, the on/off pattern indicating reception qualifications for each receiver can be modified to further add information indicating reception qualifications for each program. All these modifications are included within the scope of the present invention.

As described in detail above, if the present invention is used, encryption keys for broadcast programs can be distributed with a small amount of transmission, and recipients who are not eligible to receive the keys can use previous digital data for key distribution or Even if the receiver is turned off while digital data is being sent, the transmitted program cannot be decoded correctly, so it is extremely effective when applied to broadcasting systems.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the first invention; FIG. 2 is a block diagram showing an embodiment of the second invention;
FIG. 3 is a frame configuration diagram of the digital pattern for key distribution, and FIG. 4 is a diagram of the frame configuration of the digital pattern for key distribution.
FIG. 2 is a block diagram showing an embodiment of 02. In the figure, 102, 202 are pattern determination diagrams, 10
3, 205 is a decoder, 203 is a code converter, 10
5, 204 is an extractor, 110, 207 is a protector, 108 is a selector, 106, 107, 403
is a memory, 104 is a switch, 401 is a shift register, 402 is an exclusive OR element, 40
4 each indicates a converter.

Claims (1)

[Claims] 1. In an encryption/decryption device having a function of obtaining a key for decoding encrypted digital data from digital data sent from a transmitting side, a digital pattern input to an input terminal. pattern determining means for receiving the digital pattern and determining whether or not the digital pattern belongs to a predetermined group of patterns; 1 code converting means; extracting means for extracting a portion or none of the output depending on the output of the first code converting means; a second code converting means for converting the code of digital data input to a terminal; the pattern determining means, the first code converting means, and the second code converting means through a terminal other than the input terminal and the output terminal; and protection means for preventing access to the extraction means.