JPH058627B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a television signal transmission device using scrambled broadcasting. BACKGROUND TECHNOLOGY AND PROBLEMS Recently, contract television broadcasting has become widespread in the United States and other countries. In contract television broadcasting, only viewers who have signed a reception contract with the broadcasting station can receive normal reception, and those who do not have a contract are not able to receive normal reception. In order to prevent non-subscribers from receiving normal reception, the sending side has traditionally manipulated the video and audio signals in some way, so that when they are received by a normal receiver, the correct image and audio cannot be obtained. Methods are being used to prevent this from occurring. This method is called a scrambling method or scrambled broadcasting, and various scrambling methods have been proposed for modifying video and audio signals. For example, a method has been proposed in which the white level side and black level side of the video signal of a specific program are inverted with respect to a predetermined aliasing level, and a method in which the order of signals for a predetermined period is changed. In contract television broadcasting using such a scrambling method, viewers who have subscribed to the reception have a descrambling device for restoring (descrambling) the scrambled signal to its original form. On the transmission side of scrambled broadcasting, as will be described later, a key signal indicating a key code for decoding the scrambled signal and an address code signal indicating a subscriber number are added to the scrambled program and transmitted. ing. The above address code is used to select a subscriber who is permitted to receive messages from among a large number of subscribers; for example, the address code of a subscriber who is not permitted to receive messages (for example, a person who has not paid a fee) is sent. When the address detector installed in the descrambling device on the receiving side detects the own address (contractor number) assigned to the descrambling device from among the sent address codes, the descrambling device detects the This is done so that no scrambling operation is performed. When recording scrambled broadcasts on a VTR, the address code is obtained from the playback signal and corrected using, for example, a microcomputer.
There is a possibility that a subscriber who is not authorized to receive messages may receive them illegally. As will be described later, since the structure of the address code is relatively simple, an inexpensive microcomputer can be used for modification, and therefore there is a high possibility that the above-mentioned unauthorized reception will occur. Purpose of the Invention The object of the present invention is to increase the confidentiality of the address code by encrypting it, thereby preventing unauthorized reception as described above. SUMMARY OF THE INVENTION The present invention provides television signal transmission in which an address code signal indicating a recipient is encrypted and added to the specific program for transmission so that the television signal of a specific program can be received on the receiving side. It is related to the system. This makes it difficult to illegally decode the address code and prevents unauthorized reception of such contracted television broadcasts. Embodiments Prior to describing embodiments of the present invention, respective embodiments such as a scrambling method to which the present invention can be applied, various codes added to scrambled broadcasting, a transmitting side circuit, a receiving side circuit, etc. will be described. In addition, each of the above embodiments is based on the patent application filed in 1983, for example, which the present applicant previously filed.
-Already proposed in No. 13671. First, an embodiment of a method for scrambling a television signal will be described. In scrambled broadcasting systems, it is important to hide the contents of scrambled signals as much as possible when they are received by a normal receiver, and as mentioned above, various scrambling methods have been proposed. . Specifically, in the method of inverting the level of a signal as described above, the television signal is inverted at a predetermined field period. However, in this method, if the scrambled signal is affected by distortion in the transmission system, the original waveform will not be restored correctly when descrambling is performed on the receiving side. For example, if a signal whose level has been inverted is descrambled and re-inverted, a level difference will occur compared to the original waveform, or the waveform will be distorted. When this signal is applied to a receiver, flicker occurs at the inverted portion. This kind of flicker is particularly noticeable when the screen is almost static. Furthermore, when a scrambled broadcast program is recorded on a VTR, flickering is particularly likely to occur because the VTR has nonlinearity in both direct current and alternating current. This embodiment solves the above-mentioned flickering problem in the scrambling method that performs level inversion.
This will be explained below with reference to the drawings. First, as shown in FIG. 1A, a predetermined period T (for example, 60 seconds) is set in the television signal of a specific program to be scrambled using an index signal ID, and the screen transition portion of the program is detected and the screen is changed. Change signal (scene change signal) SC
get. Furthermore, a key signal pattern _P1 as shown in FIG. 2B is determined. The rising and falling points of this pattern _P1 are synchronized with the field period. Then, based on the signal ID, SC, and pattern _P1 , one of scramble patterns _P2 , _P3 , and _P4 for determining level inversion as shown in FIG. 1C, D, and E is created. These patterns P ₂ or P ₃ or
For example, in the high level portion of _P4 , scrambling is performed by inverting the level of the video transmission period of the television signal of a specific program. Note that the key signal pattern _P1 is repeated at a period T. Pattern _P2 is obtained by ANDing ID or SC with _P1 . Pattern _P3 is obtained by performing its rise with ID or SC and its fall with the fall of pattern _P1 . Pattern P ₄ is
This can be obtained by starting up with the AND output of ID or SC and _P1 , and falling down with SC. Various other scramble patterns for determining level inversion can be formed based on ID, SC, and _P1 . According to this embodiment, since the level inversion is always performed at the same time as the screen change, the above-mentioned screen flicker becomes less noticeable. Also, since the inversion is performed by combining the screen change and key signal pattern _P1 ,
Scrambling effect increases. Furthermore, since the descrambling method becomes difficult to decipher, security is improved. The signals ID, SC, and _P1 are each encoded with a predetermined number of bits, as will be described later, and are inserted into a predetermined position of the television signal and sent out. In this case, _P1 is inserted as a key code signal as described later. On the descrambling side, these
Detect ID, SC, P ₁ , restore the scramble pattern, and based on this scramble pattern,
Descrambling is performed to re-invert the inverted signal and restore it to its original state. Next, various signals transmitted from broadcasting stations along with scrambled specific programs and their transmission methods will be described. FIG. 2 shows the format of a scrambled broadcast television signal transmitted from a broadcasting station. In the video signal period, first a scrambled specific scramble is sent out, and then an address code, a program code, and a key code are sent out in this order. During the vertical blanking period, first the program code and the ID, SC
The code is sent out, followed by the address mode code, key mode code, stop code, etc. in that order. A scrambled program is sent out on the audio channel. Note that the audio signal may be scrambled in various ways using, for example, the scrambling pattern described above. Further, each of the above codes is transmitted as a signal obtained by NRZ modulating a binary signal of a predetermined number of bits. The address code is a coded number assigned to the subscriber in advance, and there are two types: regular mode and special mode. In the case of regular mode, when broadcasting a normal scrambled program, the broadcasting station sends out the number codes of subscribers whose reception is not permitted. When the descrambling device of the subscriber corresponding to this number detects his own number code, descrambling becomes impossible. In the special mode, when performing scramble broadcasting of special numbers, only the number codes of subscribers who have made special contracts are transmitted. Therefore, only the descrambling device that detects this number code can descramble. The key code is a decoding key code used when descrambling a scrambled signal, and has, for example, a code specifying pattern _P1 in FIG. 1. In this embodiment, this key code is added to the end of the broadcast so that descrambling cannot be performed unless the scrambled broadcast is once recorded on a VTR or the like. For example, a scrambled broadcast signal is recorded on a tape using a VTR, a key code is obtained at the end, this is stored in memory, the key code is read out during playback, and the playback signal is descrambled based on this. That is, by adding a key code to the end, it is made impossible to view the program in real time. It should be noted that the key code may be added not only to the end but also to the start of the program prior to the program, or may be divided into the start and end. Furthermore, it may be added to the start end and taken into the memory when a predetermined period of time has elapsed since it was detected (for example, when most of the program has elapsed). Next, the program code will be explained. The program code is a code that specifies a key code. The key code is changed every year, month, week, day, or program to prevent it from being decoded by anyone other than the subscriber. Therefore, when multiple programs are recorded on a tape, or when there are multiple recorded tapes, various key codes will be stored in the memory. The program code has contents unique to the program, and the program code and key code are stored in a corresponding manner in the memory. Therefore, the corresponding key code can be selected depending on the program code that is played back. In this example, this program code is
It is expressed by the broadcast date and program number. This program code is inserted into the vertical blanking period as shown in FIG. 3 along with the codes of the signals ID and SC. In addition, the program code and
The ID and SC codes are respectively inserted into the 14th and 15th horizontal scanning periods (hereinafter referred to as 14 and 15H) of the vertical blanking period. In Figure 3, the program code PC is approximately 20
70V (V: field period) is continuously inserted at second intervals. That is, PC to each 14, 15H of 70V
is inserted, and this is repeated every 20 seconds. During that time, ID and SC codes are inserted into 14 and 15H.
This is repeated until the program ends. PC and
If the ID and SC match, one can be given priority and the other can be shifted. In that case, it is better to move the PC. Note that, as shown in FIG. 2, the program code is sent out 10V prior to programming. During this 10V period, the receiving side detects that it has received scrambled broadcasting and becomes operational. As mentioned above, by adding a program code to the entire period during which the program is being sent, the program code can be detected immediately and the key code can be specified no matter where the tape is played back from. . Because of this, pause during playback,
Even if you perform fast forwarding, rewinding, etc., descrambling can be performed immediately. The address mode code is sent during the address code sending period, and indicates that the address code is currently being sent, and also indicates whether the mode is regular mode or special mode. This code is also inserted at 14 and 15H. The key mode code indicates that a key code is being sent, and is inserted in 14 and 15H. The stop code indicates that scrambled broadcasting has ended and is inserted at 14 and 15H. Next, the data structure of each code mentioned above will be explained. FIG. 4 shows the structure of the program code. This program code consists of 24 bits _d0 to _d23 and represents the year, month, day, and program number. Each bit is assigned as shown in FIG. 5 depending on the content. In Figure 4, 14 and 15H of television signal S are
Divide into two periods and allocate 1 bit to each period. Note that HD is a horizontal synchronization signal and S _B is a color burst signal. First, the first field period V ₁
A guide code indicating that it is a program code is added to 14 and 15H in the code pattern shown in the figure. Next, in the 6 fields of V ₂ to V ₇ , d ₀ to
The bit _d23 is added as shown along with the error correction codes _β0 to _β4 and bits 0. The configuration of V ₁ to _{V 7} is made into one program code as one pack, and this is repeated at approximately 20 second intervals over 70V (10 packs) as shown in FIG. Figure 6 shows the structure of the address code.
This shows the data before being encrypted according to the present invention. In the scrambled broadcasting system according to this embodiment, the number of subscribers is assumed to be, for example, several hundred thousand to several hundred thousand. This makes it impossible to represent the subscriber number with a limited number of bits. Therefore, in this embodiment, the subscribers are divided into a plurality of groups, and a number is assigned to each group. Therefore, a subscriber will have a subscriber number consisting of a group number and a number within that group. In this embodiment, the above group number is expressed as a group code using 20 bits from _d1 to _d20 , and 50 bits are used for each group.
I try to assign it to each person. And this
50 people are represented by 50 bits as a home code, and each person is assigned 1 bit. This address code is actually sent as follows. For example, if the code that allows reception is set to ``1'' and the code that does not allow reception is set to ``0'', then in a certain group represented by d ₁ to _{d 20} , subscribers number 2 and 5 are permitted to receive. If so, an address code of "d ₁ ......d ₂₀ 01001000......00" is sent. That is, the second and fifth bits of the 50-bit home code are set to ``1'' and the other bits are set to ``0'' before being transmitted. Such an address code is inserted into a video period and transmitted together with the aforementioned program code after the program ends. In FIG. 6, d ₁ to _{d 20} representing the above group codes are inserted between 30 and 34H of the signal S. still,
M ₁ and M ₂ inserted in 30H are codes that specify scrambled broadcasting, for example, codes that specify broadcast channels. Further, the above 50-bit home code is set as E ₁ to _{E 50} , and this is divided into 39 to 43H and 48 to 53H and inserted. However, E ₅₀ is inserted into 34H.
Note that C ₀ to C ₄ and P are error correction bits based on Hamming codes. Also, 36~38H, 45~47H and
The 0 bits in each section from 54 to 57H are blank times in consideration of the calculation time of the microcomputer in the descrambling device. As mentioned above, 30 to 56H represent one group of 50 people, and this is group A-1. Next, this A-
Invert all of one set of codes to make -1 set, and insert this into 57-83H. Note that this -1 set is used for error correction. Insert the next 50 people as group A-2 from 84 to 110H, then insert group -2. Similarly, A-3, -3, A-4, -
Insert each set of 4 to represent a total of 200 people. Next, insert the program code PC mentioned above into 246-251H along with bits β ₀ to β ₄ , and further insert bit 0.
Insert between 252 and 254H. Then the PC inversion code
Insert the PC into 256-261H and add the 0 bit.
Insert between 262 and 264H. If the above is considered as one pack, it will be approximately one field, and this will be repeated for even and odd fields. Repeat one pack containing 200 different people, and all the subscribers will be represented by a total of N fields. Then, these fields 1 to N are repeated four times with the same content, and the sending of the program code is completed. Note that the reason why the same content is repeated four times is to prevent detection failure on the descrambling side. Next, the key code will be explained with reference to FIG. The key code is sent during the video period after the address code is sent, and as shown in the figure, the codes d ₁ to _{d 23} are arranged in 5 bits each between 30 and 38H, and the error correction codes C ₀ to C ₄₁ , P It is expressed as Adding 3H periods of no signal of 0 bits to this is one pack, and this one pack of 9H worth of data is repeated at, for example, 10V. Next, the ID code, SC code, address mode code, key mode code and stop code will be explained with reference to FIG. Each code above has a vertical blanking period of 14,
It is inserted into 15H, 14 and 15H as shown.
5 bits are assigned to each and inserted in a predetermined code pattern. Next, a description will be given of each code having the above-mentioned data structure and the transmitting side circuit and receiving side descrambling device of the scrambled broadcast signal shown in FIG. 2 having the scrambled program. FIG. 9 shows an embodiment of a circuit for scrambling on the transmitting side. A video signal S of a specific program to be scrambled is applied to an input terminal 1, and an audio signal S _a of the program is applied to an input terminal 2. Signal S
is applied to the video scrambler 3 and also to the screen switching signal generation circuit 4 to detect the screen switching section, and for example, the signal SC shown in FIG. 3 is obtained. On the other hand, the synchronization separation circuit 5 separates the horizontal and vertical synchronization signals HD and VD from the signal S. The timing signal generation circuit 6 generates a synchronization signal and a blanking signal based on the signals HD and VD to drive the controller 7 and the data insertion circuit 8. The data insertion circuit 8 creates data for each code shown in FIG. 2 based on instructions from the controller 7, and outputs the data at a predetermined timing. In addition, the control circuit 7 creates the key code pattern P ₁ shown in FIG.
and add to audio scrambler 9. The video scrambler 3 obtains the scrambling pattern P ₂ or P ₃ or P ₄ shown in FIG. 1 based on the signal SC and the pattern P ₁ , and scrambles the signal S with this scrambling pattern. The data/video mixing circuit 10 combines the scrambled program and each code and outputs the result to the output terminal 11 as a scrambled video signal _Ss . Furthermore, the audio scrambler 9 scrambles the signal S _a and outputs it to the output terminal 12 as a scrambled audio signal S _as . FIG. 10 shows an embodiment of a descrambling device on the receiving side. Note that this descrambler is connected, for example, between a VTR and a monitor receiver. When scrambled broadcasts are recorded on tape with a VTR, the non-volatile memory 13 of the descrambling device
The program code and key code of the program are stored in correspondence with each other.
Note that the operation of this memory 13 will be described later. When the tape is played back, the played signal _S is sent from the input terminal 14 to the video descrambler 15.
The reproduced signal S _as is applied to the audio descrambler 17 from the input terminal 16 .
The synchronization separation circuit 18 extracts the signals HD and VD from the signal _S and connects the controller 19 which also serves as code detection.
and the scramblers 15 and 17, and the data separation circuit 20 extracts the data of each code from the signal _Ss and applies it to the controller 19. The controller 19 detects the ID and SC codes, as well as the program code, reads the corresponding key code from the memory 13, and applies these ID, SC, and key codes to the descramble pattern generation circuit 21. This generation circuit 21
restores a scramble pattern based on each code and adds this to the descramblers 15 and 17 as a descramble pattern. The descrambler 15 re-inverts the signal _S according to the descrambling pattern, returns it to the original signal S, and outputs it to the output terminal 22.
Output to. The descrambler 17 returns the signal S _as to the original signal S _a and outputs it to the output terminal 23 .
These output signals S, S _a are applied to the line-in terminal of the receiver. In addition, the signals S and S _a are converted to the frequency of an empty TV channel by the RF modulation circuit 24,
The signal may be applied from the output terminal 25 to the antenna terminal of the receiver. Fig. 11 is an explanatory diagram of the operation of the memory 13 during recording, and Fig. 12 shows the operation of the memory 13 during playback.
An explanatory diagram of the operation is shown. During recording, the code discriminator 2 in FIG.
7 first detects the address code and address mode code from the signal sent from the VTR.
Incidentally, during this recording, the VTR is set to recording mode E-E, and a monitor signal is applied to the descrambling device. In the regular mode, when the address code includes the own address (contractor number), the address match determination circuit 28 detects this and stops the write control circuit 29 and write counter 30. Therefore, no key code is stored in the memory 13. Then, if the address code does not include your own address, the determination unit 27
The program code and key code are stored in the memory 13 from then on. Therefore, when a plurality of programs are recorded, program codes PC ₁ to PC _N and key codes KY ₁ to _{KY N} are stored in correspondence.
In the case of special mode, it is memorized only when your address is included in the address code. During playback, the code discriminator 3 in FIG.
1 detects the program code from the reproduced data and adds it to the PC match determination circuit 33. The read counter 32 is the program code of the memory 13.
PC ₁ to PC _N are sequentially read out and added to the coincidence determination circuit 33 . being played. When the program code and the read program code match, the corresponding key code is read. ROM
For example, 30 types of descrambling pattern data are stored in 34, and the data corresponding to the read key code is read out. This data is applied to the descramble pattern generation circuit 21 shown in FIG. The above is a case where the above-described level inversion method is applied as the scrambling method, but various other scrambling methods can be applied to each embodiment. Next, an embodiment of the present invention for encrypting the address code mentioned above will be described. As mentioned above, the address code consists of a group code of _d1 to _d20 and a 50-bit home code, but here, for the sake of simplicity, the group code is assumed to be 4 bits, and the home code is assumed to be 8 bits.
In other words, one group consists of eight people. Therefore, group 1, group 2, group 3...
Each group code is “0001”, 0010”, “0011”
It is expressed as... For example, among the eight members that make up a certain group, numbers 1, 4, and 5
Assuming that subscribers No. 7, No. 8 are permitted to receive messages, their home codes will be "10011011." In this embodiment, the group code and home code are encrypted, and the above-mentioned program code is used as a key for decoding the encrypted address code in the descrambling device. There is. As mentioned above, the program code is composed of 24 bits _d0 to _d23 , and any 12 bits of these, for example " _d0 to _d11 ", are used. Now, for example, let the home code of group 1 (group code ``0001'') be ``10011011'', the home code of group 2 (group code ``0010'') be ``0110010'', and the 12-bit program code used as the key. The encryption method for "000000000001" will be described. First, the above 12-bit program code is divided into three blocks of 4 bits each as shown below.
Divide into 0000 0000 0001 Next, for each group, take the exclusive OR of the group code and block. 0001...Group 1 0000...Block 0001 ...Block --(1) 0000 0010...Group 2 0000...Block 0001 ...Block --(2) 0011 Next, use the above equations (1) and (2). Convert the 4-bit code of the answer based on the conversion table below.

[Table] This table is for converting 16 codes expressed in 4 bits to other 4 bit codes. According to this table, the answer to equation (1) above is ``0000''.
(=0) is converted to "1001" (=9), and the answers to the above equation (2) are converted to "0011" (=3) and "1100" (=C). As described above, the group code "0001" of group 1 is converted to the check bit "1001",
Group code “0010” for group 2 is “1100”
is converted into check bits. On the other hand, if each 4-bit code of the 12-bit program code block used as the key is converted according to the conversion table,

[Table] The converted 12-bit program code "100110010100" is obtained. Next, for each group, the 4-bit check bits are arranged after the 8-bit home code to form a 12-bit code, and the exclusive OR of this 12-bit code and the converted 12-bit program code is performed. Take. Through the above steps, the group code and home code are encrypted. That is, "000000101101" in the above equation (3) is sent as the encrypted address code of group 1, and "111110111000" in the above equation (4) is sent as the encrypted address code of group 2. . The encrypted address codes may be transmitted in the order of group numbers, but in order to further increase confidentiality, encryption may be further performed by changing the order of group transmission. As a method of encryption by this permutation, the permutation method shown in FIG. 13a, b...f...... is used. Further, any plurality of methods a to f may be used in combination. In that case, the 14th
As shown in the figure, a plurality of switches are switched according to an arbitrary bit of the converted program code. In the illustrated example, eight permutation methods a to h are prepared, and in order to select one, 12
Among the 8-bit program codes, 8-bit converted program codes are used. In the above embodiment, since the address code consists of a 20-bit group code and a 50-bit home code, a 5-bit conversion program code is sufficient. FIG. 14 shows an encryption circuit using an order permutation method using an 8-bit conversion program code. This encryption circuit can process codes for bit strings of 2 to the 9th power, and consists of a serial-to-parallel conversion shift register consisting of 512 flip-flops, and an 8×
It has 512 matrix-like switches (ie, multiplexers) and a parallel-to-serial conversion shift register consisting of 512 flip-flops. Therefore, 512 switches are arranged in each node. FIG. 15 also shows the encryption circuits 50 in 12 columns out of 512 columns. First, data of a 512-bit encrypted address code is sequentially loaded into the serial/parallel shift register 51 by a clock (not shown). 512 flip-flops 52 are
Each output is connected to one input of the switch 53 in the same column of the first node, and each output of the odd column is connected to the other input of the switch 53 of the even column plus 1 of the first node. Each output is connected to the other inputs of the odd-numbered switches minus 1 of the first node. Thus, each switch has one input and another input, an output, and a control input for selecting one input or the other input. Note that solid lines between flip-flops and switches, and between a switch of a certain node and a switch of the next node indicate selected wiring, and dotted lines indicate unselected wiring. The plurality of switches 53 of the first node have their control inputs connected in common and are coupled to a register corresponding to a of the conversion program code. Therefore, a
is 1, permutation a as shown in FIG.
is executed. That is, the flip-flop 52 is
Switch 5 in column 2n whose value in column 2n-1 is the first node
3, respectively, and the values of the 2n columns are output to the switches 53 of the 2n-1 columns, respectively. However, n is a positive integer of 256 or less. On the other hand, when a is 0, the values of the flip-flops of a certain example are outputted to the switches 53 in the same column of the first node. The output of each switch 53 of the first node is connected to one input of a switch 54 in the same column of the second node. Each switch 54 of the second node has an input/output and a control input, similar to the switch 53 of the first node, and the common control input is b of the conversion program code.
However, if the connection on the other input side is different from that of the previous node and b is 1, permutation b as shown in FIG. 13 is executed. That is, the switch 54 of the second node is 2 ² n
−3, ^{2 2} n−2 column value is 2 ² n−1 of the third node,
2 ² n−1, 2 ² n−1,
The values in the 2 ² n column are output to the switches 55 in the 2 ² n-3 and ^{2 2} n-2 columns of the third node, respectively. However, n is 128
is a positive integer that is less than or equal to On the other hand, if b is 0, no replacement is performed and the switch 54 of a certain column is
The values of are output to the switches 55 in the same column of the next node. Similarly, the 512 switches of the Mth node are:
Each output is connected to one input of a switch in the same column of the M+1-th node, and the same output is further connected to the other input of a switch in a predetermined column of the M+1-th node. however,
M is an integer from 3 to 7. Of course, each switch of the Mth node has a common control input coupled to a register corresponding to c-h of the conversion program code. That is ^, when c to h are 1, the permutation c to ^h shown in FIG.
2 ^M n-1 rows of switches each output, 2 ^M n-L
The column values are output to the switches in 2 ^M n-L+2 ^M-1 columns of the next node. However, n is a positive integer satisfying 2 ^M n≦512, and L is a positive integer satisfying 0≦L≦2 ^M-1 . On the other hand, if b is 0, the values of the switches in a certain column of the M-th node are output to the switches in the same column of the next node. Note that some connections are omitted in FIG. 15 for clarity. The outputs of the 512 switches 60 at the 8th node are:
It is connected to the D input of 512 flip-flops 61 of the parallel-to-serial conversion shift register. Therefore, 512
The bit encrypted address code is further encrypted by the conversion program code and retrieved by the clock. Therefore, in the illustrated case, the a, b, and ech exchange methods are used sequentially. When decoding the address code encrypted in the above manner using a descrambling device, the program code is first detected, and 12 of them from d ₀ to d ₁₁ are
Convert the bits according to the conversion table above. Based on this converted program code, the group order of the encrypted address codes is restored to the original order. Next, based on the converted program code and the address code of each group, the inverse calculations of equations (3) and (4) are performed to obtain the home code and check bit, and the two are separated. The check bits are returned to their original codes (answers to equations (1) and (2) above) using the conversion table, and the inverse calculations of equations (1) and (2) are performed to obtain the group code. Through the above steps, the home code and group code are obtained. If the home code and group code match the own home code and group code attached to the descrambler device, correct decoding has been performed. According to the encryption method according to this embodiment, the following effects can be obtained. (1) Since the program code used as the encryption key is a converted version of this code, unauthorized decoding is difficult. (2) Since it is converted into a group code and check bits, even if you try to forge an address code for unauthorized reception, it is not known what kind of check bits your own group code has been converted to, so forgery will be impossible. It becomes difficult. In the embodiment, the number of check bits is 4 bits, but
In reality, the number of check bits can be increased to the same number as the 24 bits of the program code, and since the check bits are created based on the program code, and this program code changes from program to program, it is extremely difficult to decipher the check bits. (3) Since the check bit is further converted by the program code converted together with the home code as in equations (3) and (4) above, decoding becomes even more difficult. (4) It is only necessary to prepare a program for decoding in the descrambling device, and there is no need to add a special signal for decoding to the broadcast signal. (5) Due to the effects of (1), (2), and (3) above, an expensive decoding device is required to perform unauthorized reception, so unauthorized reception becomes virtually impossible. Effects of the Invention The confidentiality of address codes can be dramatically improved, and unauthorized reception of such contracted television broadcasts can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a timing chart showing an example of a scrambling method applicable to the present invention, Fig. 2 is a diagram showing an example of the format of each signal sent in scrambled broadcasting, and Fig. 3 is a diagram showing a program code and other codes. 4 is a diagram showing an example of the data structure of the program code, FIG. 5 is a diagram showing the relationship between the content of the program code and the bits, and FIG. 6 is an example of the data structure of the address code. 7 is a diagram showing an example of the data structure of a key code, FIG. 8 is a diagram showing an example of the data structure of other various codes, FIG. 9 is a circuit block diagram showing an embodiment of the transmitting circuit, and FIG. The figure is a circuit block diagram showing an embodiment of the decoder, FIG. 11 is a block diagram explaining the operation of the memory during recording, and FIG.
FIG. 2 is a block diagram illustrating the operation of the memory during playback, FIG. 13 is a diagram illustrating the encryption method by group replacement according to the present invention, and FIG. 14 is a block diagram illustrating an embodiment of the above method. FIG. 15 is a schematic partial circuit diagram in which the nodes shown in FIG. 14 are expanded two-dimensionally. In addition, in the symbols used in the drawings, 8...data insertion circuit, 28...address match determination circuit,
33...A program code match determination circuit.

Claims (1)

[Claims] 1. A scrambled specific program, a program code signal specifying the specific program, and an address code signal indicating a recipient who can receive the specific program and encrypted by the program code signal. a controller configured to receive a television signal, the controller having permission to restore the encrypted address code signal based on the program code signal sent at the same time as the program code signal and to descramble the specific program. A television signal transmission device characterized in that: 2. The transmission device according to claim 1, wherein the controller restores the encrypted address code signal by an exclusive OR method based on the program code signal. 3. The transmission device according to claim 1, wherein the controller restores the encrypted address code signal by a reordering method based on the program code signal. 4. According to any one of claims 1 to 3, the recipients are divided into a predetermined number of groups, and each group is transmitted using the program code signal as a key and rearranging the order of the groups. transmission equipment.