JPH09307872A - Pay broadcast system and its encoder and decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce number of transmission times for individual information. SOLUTION: A ciphering circuit 105 ciphers a 1st substantial work key and conversion data. As a key of a ciphering circuit 107, the 1st work key or a 2nd work key obtained by converting the 1st work key with conversion data is used. A decoding circuit 125 recovers the 1st work key and the conversion data. A conversion circuit 202 converts the 1st work key by the conversion data to generate a 2nd work key. A decoding circuit 131 uses the 1st or 23nd work key corresponding to the ciphered key of the ciphering circuit 107.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pay broadcasting system and its encoder and decoder.

[0002]

2. Description of the Related Art In pay broadcasting, video and audio signals are scrambled so that only those who have a contract can enjoy the broadcast.

There are roughly two processes for descrambling. One is a process of descrambling the video and audio signals and restoring the original signals. The other is a process of determining whether or not the descramble can be descrambled, that is, a process of comparing the contract status with the broadcasting station and judging, and managing ON / OFF of the descramble process. There are two.

In this contract management processing, the information sent from the broadcasting station is used, but the information is encrypted so that only the decoder of the contractor can take in the information.

FIG. 8 shows the configuration of a conventional pay broadcasting system. As illustrated, the data to be encrypted has a hierarchical structure.

[0006] The encryption circuit 105 is supplied with individual contract information (hereinafter referred to as individual information) from the broadcasting station to each decoder and a work key Kw to be encrypted. The individual information is information for allowing the decoder of the contracted person to view. In the encryption circuit 105, the individual key Kmi (i
Is added to indicate that the individual key is different for each decoder). The encryption circuit 105 encrypts the individual information and the work key Kw with the individual key Kmi.

For this reason, the decoder that does not have the individual key cannot take in the encrypted information, so that it is not possible to perform fraudulently looking at the information of another person. However, as a matter of course, since the individual keys are different from each other, in order to control 100,000 decoders, it is necessary to send 100,000 pieces of this individual information. It is necessary to send the data, and as the number of decoders to manage increases, the amount of data to send also increases, which is difficult.

The work key Kw is a key for encrypting program information, which will be described later, so that it will not be illegally used. Work key K so that it is difficult to analyze the encryption method itself
It is said that w needs to be changed regularly.

This is because there is a risk that the work key Kw and the encryption method itself will be analyzed from the relationship between the encrypted program information and a later-described scramble key Ks which is a part of the decryption result. To reduce that risk,
The idea is to change the work key Kw.

Therefore, for example, the broadcast station gives individual information including the work key Kw to the decoder so that the work key Kw is updated at a timing of once a month or once a year. .

The encryption circuit 107 is supplied with information about a program commonly given to each decoder (hereinafter referred to as program information) and a scramble key Ks, which are encrypted. The encryption circuit 107 encrypts the program information and the scramble key Ks with the work key Kw.

The scramble circuit 109 is supplied with video and audio signals to be encrypted. The scramble circuit 109 encrypts the video and audio signals with the scramble key Ks.

The multiplexing circuit 111 includes an encryption circuit 105,
The signals from the encryption circuit 107 and the scramble circuit 109 are multiplexed. The multiplexed signal is transmitted to the decoder side.

The separation circuit 121 separates the inputs, descrambles the output signal of the encryption circuit 105 to the decryption circuit 125, the output signal of the encryption circuit 107 to the decryption circuit 131, and the output signal of the scramble circuit 109. Supply to the circuit 137.

The decryption circuit 125 decrypts the output signal of the encryption circuit 105 with the individual key Kmi from the individual key Kmi memory 123, and reproduces the individual information and the work key Kw.
The individual information is stored in the individual information memory 127, and the work key Kw is stored in the work key Kw memory 129.

The decryption circuit 131 decrypts the output signal of the encryption circuit 107 with the work key Kw from the work key Kw memory 129 and reproduces the program information and the scramble key Ks. The scramble key Ks is supplied to the switch 135.

The condition comparison circuit 133 includes the individual information memory 1
The individual information from 27 and the program information from the decoding circuit 131 are compared, and if viewing is possible, the switch 135 is turned on. As a result, the scramble key Ks is supplied to the descramble circuit 137.

The descramble circuit 137 decrypts the output signal of the scramble circuit 109 with the scramble key Ks and reproduces the video and audio signals.

[0019]

As described above, since the individual key Kmi is different for each decoder, in order to update the work key Kw and give it to each decoder, it is necessary to send the individual information for the number of units. However, as the number of decoders increases, the amount of data for sending individual information becomes enormous, and measures such as increasing the channel capacity for sending data or taking the time required to control all decoders are taken. Had to take.

Therefore, an object of the present invention is to provide a pay broadcasting system which does not need to send individual information each time the work key is updated, and an encoder and a decoder thereof.

[0021]

[Means for Solving the Problems]

(Paid broadcasting system) In a pay broadcasting having an encryption structure of at least three layers, individual information by the first key of the third layer,
A second key of the second layer, a first encryption means for encrypting the conversion data of the second key, and the second key or the second key
Second encryption means for encrypting the program information and the scramble key with the third key obtained by converting the key of the above with the conversion data, and the output of the first decryption means with the first key. From the first storage means for storing the second information, the first decryption means for reproducing the individual information, the second key, and the converted data, Of the second key for converting the second key by the conversion data to generate the third key, second storage means for storing the third key from the conversion means, and the first A second key that decrypts the output of the second encryption unit with the second key from the storage unit or the third key from the second storage unit to reproduce the program information and the scramble key. And a decoding means of.

(Encoder) In an encoder having an encryption structure of at least three layers, the individual information, the second key of the second layer, and the conversion data of the second key are encrypted by the first key of the third layer. And a second encryption for encrypting the program information and the scramble key with a third key obtained by converting the second key or the second key with the conversion data. Means and are provided.

(Decoder) It has an encryption structure of at least three layers, and encrypts the individual information, the second key of the second layer, and the conversion data of the second key by the first key of the third layer. Second encryption means for encrypting the program information and the scramble key with a first encryption means and a third key obtained by converting the second key or the second key with the conversion data. And a decoder for receiving a broadcast transmitted from an encoder, comprising: decoding the output of the first decoding means with the first key;
Key, first decryption means for reproducing the converted data,
First storage means for storing the second key; conversion means for converting the second key from the first storage means with the conversion data to generate the third key; Second storage means for storing said third key from said means and said second key from said first storage means or said third key from said second storage means And a second decryption means for decrypting the output of the encryption means and reproducing the program information and the scramble key.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of a pay broadcasting system of the present invention. Circuits that operate in the same manner as in the conventional example will be assigned the same reference numerals and description thereof will be omitted.

The encryption circuit 105 is supplied with individual information (contract information), a first work key Kw1 which is an original work key, and conversion data for converting the first work key Kw1. The conversion data is the future first work key Kw1.
This is to preempt the conversion of. Encryption circuit 10
5 is the individual information by the individual key Kmi, the first work key,
Encrypt the converted data. The encrypted data string is shown in FIG.

The scramble key Ks is sent to the encryption circuit 107.
And program information is supplied. The encryption circuit 107 encrypts the scramble key Ks and the program information with the first work key Kw1 or the second work key Kw2.

The second work key Kw2 is obtained by converting the first work key Kw1 with the conversion data. An example of the converted data and a second generated by this converted data
An example of the work key Kw2 will be described below.

A first example of the conversion data is data for changing the order of the bits of the first work key Kw1. An example of conversion in this case is shown in FIG. The second example of the conversion data is data indicating the rotation direction and the rotation amount of the data of the first work key Kw1. For example, 2 to the right
Rotate by a bit. An example of conversion in this case is shown in FIG. The third example of the conversion data is the first work key Kw.
This is data for instructing the inversion of the bit order of 1. An example of conversion in this case is shown in FIG. A fourth example of the converted data is to instruct addition to each bit of the first work key Kw1,
This is the data to be added. An example of conversion in this case is shown in FIG.
Shown in The conversion data sent by the encryption circuit 105 is
Not limited to one type, it is possible to send a plurality of types.

A flag is inserted in the output of the encryption circuit 107. In the encryption circuit 107, the flag is
It is data of which work key was used and data of the type of conversion data.

FIG. 3 shows the encrypted program information including the flag and the data string of the scramble key Ks.

The decryption circuit 125 decrypts with the individual key Kmi, and outputs the individual information, the first work key Kw1, and the conversion data. The first work key Kw1 is the first
The work key Kw1 is supplied to the memory 201. The conversion data is supplied to the conversion circuit 202. Conversion circuit 20
The first work key Kw1 is supplied to the second work key Kw1 from the memory 201. The conversion circuit 202 is
As described above, the first work key K is obtained from the conversion data.
w1 is converted to generate the second work key Kw2, and the second work key Kw2 is generated.
The work key Kw2 is supplied to the memory 203. Each memory 2
01 and 203 from the first and second work keys Kw1 and Kw
2 is supplied to the switch 207.

The flag detection circuit 205 detects a flag and detects which work key is used in the encryption circuit 107. The flag detection circuit 205 sets the switch 207 to the first position when the first work key Kw1 is used.
If the second work key Kw2 is used, the switch 207 is moved to the second work key Kw2 memory 203 side. The flag detection circuit 205 also detects which conversion data has been used and selects the type of the second work key Kw2 to be read from the second work key Kw2 memory.

The decryption circuit 131 decrypts with the work key selected by the switch 207 and outputs the program information and the scramble key Ks.

The conversion data may be a combination of a plurality of conversion methods. For example, the conversion shown in FIG. 5 may be performed after the conversion shown in FIG.

When there is only one type of converted data, the insertion of flags on the encoder side is stopped and the flag detection circuit 20 is used.
5 is omitted. In this case, the decryption circuit 131 sequentially selects and matches the first and second work keys Kw1 and Kw2.

Further, in the group individual information, not only the work key for the decoder included in the group but also the contract information (group individual information) is given.
It is inconvenient because the contract information cannot be given except for the decoder that does not want to update the work key. However, in the present invention, since the contract information already stored in the decoder is used as it is, such inconvenience is caused. There is no need to change the work key.

[0037]

As described above, according to the present invention, one or more pieces of data for converting the original first work key Kw1 are put in advance in the individual information, and the first work key Kw1 is stored when decrypting the program information. Since the converted data is used after conversion, it is not necessary to send individual information only for changing the work key, and the transmission channel can be effectively used.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a pay broadcasting system of the present invention.

FIG. 2 is a diagram showing a data string of encrypted individual information.

FIG. 3 is a diagram showing a data string of encrypted program information and a scramble key Ks.

FIG. 4 is a diagram showing an example of conversion of an original first work key Kw1.

FIG. 5 is a diagram showing a conversion example of an original first work key Kw1.

FIG. 6 is a diagram showing an example of conversion of an original first work key Kw1.

FIG. 7 is a diagram showing a conversion example of an original first work key Kw1.

FIG. 8 is a diagram showing a configuration of a conventional pay broadcasting system.

[Explanation of symbols]

103 ... Individual key file, 105, 107 ... Encryption circuit, 109 ... Scramble circuit, 111 ...
-Multiplexing circuit, 121 ... Separation circuit, 123 ... Individual key Kmi memory, 125 ... Decryption circuit, 127 ...
..Individual information memory, 131 ... Decoding circuit, 133
... Condition comparison circuit, 135 ... Switch, 137
Descrambling circuit, 201 ... First work key Kw1 memory, 202 ... Conversion circuit, 203 ... Second work key Kw2 memory, 207 ... Switch

Claims (15)

[Claims] 1. In pay broadcasting having an encryption structure of at least three layers, individual information, a second key of a second layer, and conversion data of the second key are encrypted by a first key of a third layer. And a second encryption that encrypts the program information and the scramble key with a third key obtained by converting the second key or the second key with the conversion data. Means, a first decryption means for decrypting the output of the first decryption means with the first key, and reproducing the individual information, the second key, and the converted data, and the second decryption means. First storage means for storing a key; conversion means for converting the second key from the first storage means with the conversion data to generate the third key; Second storage means for storing a third key; and the second storage means from the first storage means. 2 of the key or the second
A second decryption means for decrypting the output of the second encryption means with the third key from the storage means, and reproducing the program information and the scramble key. Pay broadcasting system. 2. The pay broadcasting system according to claim 1, wherein the conversion data is data for changing the order of each bit of the second key. 3. The pay broadcasting system according to claim 1, wherein the conversion data is data indicating a rotation direction and a rotation amount of the data of the second key. 4. The pay broadcasting system according to claim 1, wherein the conversion data is data instructing to invert a bit order of the second key. 5. The pay broadcasting system according to claim 1, wherein the conversion data is addition data to the second key. 6. An encoder having an encryption structure of at least three layers, wherein individual information, a second key of a second layer, and conversion data of the second key are encrypted by a first key of a third layer. A first encryption unit, and a second encryption unit that encrypts the program information and the scramble key with the second key or a third key obtained by converting the second key with the conversion data. An encoder comprising: 7. The encoder according to claim 6, wherein the converted data is data for changing the order of each bit of the second key. 8. The encoder according to claim 6, wherein the conversion data is data indicating a rotation direction and a rotation amount of the data of the second key. 9. The encoder according to claim 6, wherein the conversion data is data instructing to invert a bit order of the second key. 10. The encoder according to claim 6, wherein the conversion data is addition data to the second key. 11. A method for encrypting individual information, a second key of a second layer, and conversion data of the second key, which has an encryption structure of at least three layers, and which uses a first key of a third layer. A second encryption means, and a second encryption means for encrypting the program information and the scramble key with a third key obtained by converting the second key or the second key with the conversion data. In a decoder for receiving a broadcast transmitted from an encoder, the output of the first decryption means is decrypted by the first key, and the individual information, the second key, and the converted data are decrypted. First decryption means for reproducing, first storage means for storing the second key, and the second key from the first storage means converted by the conversion data to generate the third key. Converting means for generating a key, and the third key from the converting means Second storing means for 憶, the second key from the first storage means or the second
A second decryption means for decrypting the output of the second encryption means with the third key from the storage means, and reproducing the program information and the scramble key. decoder. 12. The decoder according to claim 11, wherein the conversion data is data for changing the order of the bits of the second key. 13. The decoder according to claim 11, wherein the conversion data is data indicating a rotation direction and a rotation amount of the data of the second key. 14. The decoder according to claim 11, wherein the conversion data is data instructing to invert a bit order of the second key. 15. The decoder according to claim 11, wherein the conversion data is addition data to the second key.