JPS6259960B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wireless pay television system, and more particularly to an improvement in its key code generation method.

As is well known, a wireless pay television system is intended only for subscribers who have signed a contract with a broadcasting station.The broadcasting station transmits a television signal encrypted by an encoder, and the subscriber side decodes this encrypted television signal. In this system, the key code used for encoding on the broadcasting station side and the key code used for decoding on the subscriber side are made to match or correspond, and the key code used for decoding on the subscriber side is An enable code must be received from the station to the subscriber indicating the status of the encoding.

Figure 1 shows such a wireless pay television system.
It shows the basic configuration of the system, where 1 is an encoder on the broadcasting station side, 2 is a transmitting device, and 3 is a signal source. Signal source 3 is the program to be transmitted (video, audio)
is the source of the television signal before encryption.
The encoder 1 basically consists of an encoding circuit 4 and a key code generation circuit 5. Here, the key code is basic data that determines the encryption state in the encoding circuit 4. Encoding circuit 4
encrypts a television signal using a known method, and an enable code indicating the encryption state is superimposed on the encrypted television signal.

The transmitting device 2 converts the encrypted television signal into radio waves A and transmits them.

The receiving system on the subscriber side consists of a decoder 6 and a conventional television receiver 7. The decoder 6 includes a receiving circuit 8, a decoding circuit 9, and a key code circuit 10. The receiving circuit 8 receives the encrypted television radio waves, converts the received signal into a signal in a format that is easy to process by the decoding circuit 9 (for example, a baseband video signal or audio signal), and also converts the received signal into a signal such as an enable code, a program number, etc. A decoding circuit 9 detects the code and uses it as a received signal.
supply to

The decoding circuit 9 decodes the encrypted television signal using a decode signal, converts it into a pre-encrypted television signal that can be played back on a normal television receiver 7, and outputs it to the television receiver 7.

The key code circuit 10 generates a key code corresponding to the key code on the transmitting side, and FIGS. 2a and 2b show the configuration of a conventional key code circuit. In figures a and b, 11 is a memory, 12 is a memory control circuit, 13 is a key code register, and 14 is an arithmetic circuit.

In the key code circuit shown in FIG. 2a, a plurality of key code data are written in the memory 11, and the data can be rewritten by data transmission via a telephone line or the like. Memory control circuit 1
2 accesses the memory 11 in response to the program number PB, outputs the corresponding key code K from a predetermined area thereof, and stores it in the key code register 13.

In the key code circuit shown in FIG. 2b, the memory 11 can be rewritten by the subscriber's operation, and stores one type of key code data. The memory control circuit 12 is a program
Controls the data output from the memory 12 in response to the number PB and supplies it to the arithmetic circuit 14, which causes the circuit to perform a predetermined arithmetic operation with the program number PB and generate a corresponding key code K;
It is stored in the key code register 13.

The conventional key code circuit shown in FIG. When you receive a program number, which is a specific signal that comes
A system is adopted in which data corresponding to the program number is read out of the data and a key code is generated.

According to such a key code generation method, the receiving system has conventionally been configured using an electrically rewritable semiconductor memory as the memory.
Not only does the system become large-scale, but it also requires an uninterrupted power supply to maintain the memory contents of the semiconductor memory, making it expensive.

Furthermore, in the conventional key code circuit shown in FIG. The type of information is restricted by the valid number of program numbers, reducing confidentiality. Furthermore, there is a problem that even if a mechanical switch is used, it is not necessarily possible to reduce the cost due to concerns about subscriber's erroneous operation.

The present invention has been made in order to improve the problems of the prior art, and it sets and holds key code data in a memory corresponding to arithmetic circuits with different arithmetic contents for each decoder, and also stores data from the memory. The key code is processed by an arithmetic circuit and stored in a key code register, and in response to a read signal from a decoding circuit, the key code is read from the register and supplied to the decoding circuit.

The present invention will be described below with reference to the embodiment shown in the drawings. In FIG. 3, a key code circuit 10N includes a memory 16N, an arithmetic circuit 17N, and a key code register 18, corresponding to a decoder 6N. The memory 16N has a different arithmetic circuit 1 for each decoder 6N.
Key code data is set corresponding to 7N,
The data is retained.

The arithmetic circuit 17N performs predetermined arithmetic processing on the data from the memory 16N and outputs it to the key code register 18. The key code register 18 stores the key code from the arithmetic circuit 17N, and supplies the stored key code to the decode circuit 9 in response to a read signal from the decode circuit 9. The read signal can be generated using the program number PB as in the past, but it may also be generated separately.

4 and 5 show the memories 16 ₁ and 1, respectively.
6 ₂ , a specific configuration example of the arithmetic circuits 17 ₁ , 17 ₂ and the key code registers 18 ₁ , 18 ₂ is shown. In the figure, memories 16 ₁ , 16 ₂ and arithmetic circuit 1
7 ₁ and 17 ₂ are described as using mechanical switches M ₁ and M ₂ for ease of understanding, but it is of course not limited to this, and can be used with semiconductor memory, punch cards, magnetic cards, etc. It suffices as long as it is readable. Further, the key code registers 15 ₁ and 15 ₂ are 4-bit binary registers, for example.

As is clear from FIGS. 4 and 5, the arithmetic circuits 17 ₁ and 17 ₂ perform different arithmetic processes, and therefore the corresponding memories 16 ₁ and 16 ₂ also have different keys. Code/data is set and retained.

That is, the memory 16 ₁ is connected to the corresponding arithmetic circuit 17 ₁
According to the above, it is set to "1011". However, in actual operation, it is desirable to update the key code as appropriate from the viewpoint of confidentiality, and the memory ₁₆₁ is also updated accordingly.

When the decoder is set to the operating state, the decoding circuit 9 generates a program number PB as a read signal at a predetermined timing from the received signal, and supplies it to the key code register ₁₈₁ , although no regular key code has been input. do. This program number PB acts as a data load signal for the 4-bit key code register ₁₈₁ , which causes the register to read and store the key code input from the arithmetic circuit ₁₇₁ .

On the other hand, the stored content "1011" in the memory ₁₆₁ is changed in the weight of each bit by the arithmetic circuit ₁₇₁ , and is output as "1101" as is clear from the figure, and as described above, it is outputted as "1101" by the program number PB. The key code register ₁₈₁ stores the key code "1101" and supplies it to the decoding circuit 9. When this code is a regular key code, the decoding circuit 9 supplies a decoded output (decoded television signal) to a television receiver (not shown), as in the conventional system.

In this case, if the contents of the memory ₁₆₁ are set to "1110", which is the contents of the memory ₁₆₂ , for example, the output of the key code register ₁₈₁ will be "1011", which is not a regular key code. Since they do not match, the decoding circuit 9 is unable to generate a decoded output.

Further, in the embodiment described above, a 4-bit binary code is used as the key code, but it is needless to say that the key code is not limited to this.

Now, enter the key code in the encoder as “1101”
Assuming that, in order to make the decoding circuit perform a normal decoding operation, the output of the key code register must be KA=1, KB=1,
It is necessary that KC=0 and KD=1.

In the embodiments of FIGS. 4 and 5, it is clear that if each arithmetic circuit executes the illustrated operation contents, each memory will have the illustrated memory contents. For example, in the case of the embodiment shown in FIG. 4, the arithmetic circuit ₁₇₁ performs the following operations: Input A → Output A Input D → Output B Input B → Output C Input C → Output D A, D, B, C]
It will be displayed as

At that time, output A=1, output B=1, output C=
0, to obtain output D=1, the contents of memory ₁₆₁ are A=1, B=0, C=1, D=1,
This is symbolized and expressed as M[1, 0, 1, 1]. The contents of the key code register ₁₈₁ are similarly encoded and displayed as K[1, 1, 0, 1]. Therefore, in the case of Fig. 4, this K[1, 1, 0, 1] is K[1, 1, 0, 1] = M[1, 0, 1, 1] × F[A, D, B, C] In the case of Fig. 5, it can be expressed as K[1, 1, 0, 1] = M[1, 1, 1, 0] x F[B, A, D, C], and each example You can see that the memory contents are different.

When we consider another 4-bit calculation format F [ ] of the calculation circuit using the notation described above, we find that F
Since the content in parentheses [ ] follows the permutation of the four elements, there are as many types of calculation formats as there are permutations above, so for the four elements F [A, B, C, D], there are _{4 P4} =4! = 24 ways.

On the other hand, in a binary number, once the value is determined, the type of value that can be expressed is determined by the number of "1" (or "0") contained therein, and that number is determined by the binomial coefficient. . For example, if it is 4 bits in binary, it will be as follows.

Number of 1 Types of numbers that can be expressed 0 ₄ C ₀ = 4! /0!4! = 1 1 ₄ C ₁ = 4 2 ₄ C ₂ = 6 3 ₄ C ₃ = 4 4 ₄ C ₄ = 1 Total 16 Therefore, it has substantially different values (contents) depending on the value of the required key code. The number of memories will be fixed instead of 24 types. For practical purposes, it is preferable to use a code with a large number of bits, and in the case of a 16-bit configuration, it is as follows.

Type of arithmetic circuit = ₁₆ P ₁₆ = 16! =
20912789888000 Number of 1 Types of numbers that can be expressed 0 ₁₆ C ₀ = 1 1 16 2 120 3 560 4 1820 5 4368 6 8008 7 11440 8 12870 9 11440 10 8008 11 4368 12 1820 13 560 14 120 15 16 16 1 Thus the key If a binary code containing 6 to 10 "1"s is used as the code, approximately 10,000 types of memory contents can be set, which is sufficient for practical use.

In that case, the total number of key codes is (8008 + 11440) x 2 + 12870 = 51766, which provides a sufficient number of types. Of course, depending on the case, it may be possible to set a key code with a smaller number of bits.

As is clear from the above explanation, according to the present invention, it is possible to provide a highly confidential, inexpensive, and reliable method for generating a key code on the receiving side that matches that on the transmitting side, and the practical effects are significant. be.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic configuration of a wireless pay television system, Fig. 2 a and b are block diagrams showing conventional key code generation methods, and Fig. 3 shows an embodiment of the present invention. The block diagrams shown in FIGS. 4 and 5 are schematic diagrams showing specific configuration examples of a memory and an arithmetic circuit, respectively, in the present invention. 6N...Decoder, 10N...Key code circuit, 16N...Memory, 17N...Arithmetic circuit, 1
8N...Key code register.

Claims (1)

[Claims] 1 In a pay television system in which a television signal encrypted using a key code by an encoder on the transmitting side is decoded by a decoder on the receiving side using a key code that matches the above key code, each decoder An arithmetic circuit with different operation contents is provided for each arithmetic circuit, key code data is set and held in a memory provided corresponding to the arithmetic circuit, and data from the memory is processed by the above arithmetic circuit to create a key code register. 2. A key code generation method, characterized in that the key code is stored in the key code register, and is configured to read out the key code from the key code register and supply it to the decoding circuit in response to a read signal from the decoding circuit.