JPS60183842A - Transmission system - Google Patents

Abstract

PURPOSE:To enhance the secrecy of transmission contents and to facilitate operation of a system by using three-layered keys whose change periods are short, long and fixed. CONSTITUTION:In a broadcasting station 31, a program signal is ciphered in a scrambler 35. This ciphering is designated by a bit string (key Ks) from a code generator 37, and the key Ks is ciphered in a ciphering device 39 by a bit string (key K) from a code generator 41. Further, the key K is ciphered in a ciphering device 45 by an individual key KM of an individual key file 47. The key KM corresponds to each receiving station 33. A separating device 49 in the receiving station 33 separates said scrambled signal and the signal ciphered into the key Ks from each other. Algorithms having relations of reversed function are designated to corresponding ciphering devices and deciphering devices in both stations by the same key. Thus, the key Ks having a long period is ciphered by the common key K having a long period, and the key K is ciphered by the key KM which has a long period or is peculiar to the receiving station.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a transmission system for individually and secretly transmitting information, and to this transmission system.

[Technical background of the invention and its problems]

A format in which information is transmitted individually and confidentially is suitable as a transmission format for pay broadcasting. As shown in Figure 1, this transmission form generally consists of a scrambler (1υ) at one transmitting station and descramblers (1υ, etc.) at multiple receivers. In this system, it is necessary that the key Ks that specifies encryption and decryption in the scram 20υ and the descrambler + 131 is common. It is necessary to decide whether to distribute the information to each recipient individually.

Conceptually, the code generator (15) at the transmitting station generates the key 8, supplies this to the scrambler 1ll)K, and sends it to each receiver via the encoder a'7). To distribute. At each recipient side, the decryption is performed by a decryptor (!J), the key Ks is returned, and this is supplied to the scrambler (13) to obtain the original signal that was input to the scrambler (II).

In this way, it has been achieved to distribute 13 ?
The problem is how to specify encryption and decryption in 11.

As one of these methods, there is a common method. This method is the first
As shown in the figure, encryption and decryption in the encoder L1n and the post-encryptor ill are specified using the same fixed key.

In this system, anyone can obtain information from the transmitting station as long as they have access to a discrambler (including 9 signal means) and a decoder; broadcast), descrambler (+3s &
The joint concave was commercially available, and had the disadvantage of having weak security.

Therefore, as a method to achieve stronger security, 1.
Individual key schemes have been proposed. As shown in Figure 2, this method encrypts the key Ks generated from the code generator (15) in the encoder 17) with an individual key corresponding to each recipient. It is necessary for transmitting signals. On the receiving side, the decryptor (191) obtains ml Ks using individual keys provided for each receiver rc. In such a system, if the key Ks from the code generator 09 is frequently changed, Accordingly, the data related to the keys sent to individual recipients is frequently changed, and only subscribers who have individual keys can obtain the correct key, significantly improving system security. .

However, in this system, in order to increase security, the update interval of the key Ks must be shortened, but each time the key Ks is updated, the key Ks is encrypted and different information is transmitted to each recipient. Therefore, key distribution requires a large transmission capacity.This means that it is not possible to increase the number of subscribers at the same time as the negative phase of the hardware increases. .

[Purpose of the invention]

The object of the present invention is to eliminate the above-mentioned drawbacks and provide a transmission system that is easy to operate for security, IJ, etc., and at the same time provides a transmission device and a reception device for this transmission system. The purpose is to

The invention comprises a first signal converting means for converting a significant signal from a signal source according to a single algorithm;
a first means for transmitting the signal from the signal converting means to the receiving means of the number of slots; and a second signal converting means for converting the signal from the means to the significant I-sign after receiving the signal. A third signal converting means converting the key information of 2$1 specifying the first algorithm according to the second algorithm, and a second algorithm in the third signal converting means. The second key information pointed out is the third key information.
a fourth signal converting means for converting according to an algorithm; a second means for distributing each of the outputs of the third and fourth signal converting means to the receiving means; and a fourth signal sent by the means. a fifth signal converting means for converting the output of the converting means into information corresponding to the second key information according to an algorithm corresponding to the third algorithm;
a sixth signal converting means for obtaining information corresponding to the first key information Qζ from the output of the third signal converting means using the i11 information obtained by the signal converting means; The second signal conversion means is operated based on the information obtained by the conversion means.

〔Effect of the invention〕

In the present invention, even if a third party obtains the second signal conversion means, which is a descrambler, and discovers the conversion algorithm of this conversion means, the conversion and inverse Y conversion algorithm will be changed.

Eavesdropping will immediately become impossible, and the exclusivity and integrity of the transmission system will become extremely high.

[Embodiments of the invention]

First, a basic embodiment will be explained. This embodiment relates to a pay television system, as shown in Figure 2B3. This system consists of at least one broadcast station (31)
and a plurality of receiving stations (3, 9). Information is transmitted between the broadcasting station (1) and the receiving station (A) by wire or wirelessly.In terms of system flexibility, wireless,
That is, it is preferable to transmit information as radio waves.

The broadcasting station (30) encrypts the signal representing the program content,
The data is transmitted to each receiving station B:3), and each valid receiving station ((3) decrypts the encryption to obtain meaningful information.

First, the broadcasting station (31) encrypts a signal representing the program content (hereinafter referred to as a street signal) using the scrambler 5). Let us clarify the meaning of this encryption. Program No. 18 before being encrypted is, for example, a significant signal for commercially available TV receivers, FM receivers, etc. (not shown), and when input to these receivers, it is a significant signal. can be played. On the other hand, the scrambler ff (51) converts the signal into a form that cannot be established as information even if it is input directly to the playback device. A signal subjected to such conversion is called a scrambler signal. Scrump AI (,35
1 is the digital bit string output from the first code generator (31). This is called the key Ks of the scram 9 (35). This key Ks is: The first encoder (3!l) is encrypted. This encoder C39) is encrypted according to the US data encryption standard (Data:ucryption 5tand).
It is sufficient to use an encryptor according to the algorithm of ard).

ml encoder (algorithm of conversion in arrogance, i.e.
The method of changing the digital bit string is specified by MK, which is the digital bit string from the second code generator (4I). The output of the first encoder 09 is sent to a multiplexer (on the 4th floor, for example, in the form of radio waves, and sent to each receiving station C33) along with the output of the scrambler.
sent to.

On the other hand, the digital bit string from the second code generator (4υ) is processed by the second encoder (4υ) on the transmitting station (31) side, for example.
5) and sent to the receiving station. The second encoder (45), like the first encoder (U), is an encoder that follows the algorithm of the US data encryption standard. , to the receiving station.The second encoder (43), like the first encoder (111), is an encoder that follows the algorithm of the US data encryption standard. The four encryption algorithms U are identified by the individual key KM read out from the i-side key file (47) 7>.This individual key file (
47) stores an individual key corresponding to each receiving station 63) (subscriber).

In contrast to these 6 transmitting stations, the receiving station (33) is
It includes a demultiplexing device (49) that receives the multiplexed signal from the multiplexing device (4) and separates the received multiplexed signal. The scrambled signal is supplied to the descrambler 0, and the signal obtained by encrypting the key Ks is supplied to the first encoder 0.

On the other hand, the signal from the second encoder (4) on the transmitting station (b) side is supplied to six second decoders on the receiving station (c) side.

The decoding algorithm using the 6 second post-coders is as follows.

The receiving station is specified by an individual key distributed in advance to the receiving station. The second encryptor (451 and the second decoder 6J are designated with algorithms that are mutually inverse functions using the same key, and the second decoder 65
) will be the same as the output of the second code generator (4υ).

The output of the second decoder 155) further specifies the algorithm of the first postcoder 4531. first encoder C3
9) and the first decoder mark, when algorithms are specified using the same key, conversion algorithms that are inversely converted to each other are respectively specified, and in this state, the first decoder mark (
When the output of the first decoder 63) is inputted to the first decoder 63), the output of the first decoder becomes the same as the input Ks of the encoder 0 of =1. This key Ks is supplied to the descrambler 6D, and the conversion algorithm in the descrambler 6υ is specified. This descrambler (5I) is also a counterpart to the scrambler (arrogant), and when the same key is supplied,
Algorithms that are inverse transformations of each other are identified,
In this state, when the output of the scrambler C35) is supplied to the disc lamp':)e31), a program signal, which is the input to the scrambler G9, is obtained.

In such a configuration, the output of the first code generator is frequently changed. For example, it is preferable to synchronize changes in the program signal input to the scrambler (39). That is, each time the program changes, the output of the code generator C37 is changed accordingly. For example, the code generator 6 may be constituted by a random number generator, and the code (number 8) corresponding to the change point of the program (number g) may be input to the random number generator.

As a result, the key number 8 changes from program to program.

Therefore, in the scrambler G3, the program signal is changed into a different signal format each time the program changes.

If the program signal is a digital signal, it may have the same configuration as the first encoder 01 described above, and a scrambled signal can be obtained by converting the signal sequence.

If Father 1 program No. 1a is analog (No. N), all of the multiple im conversion methods may be prepared, and one signal conversion machismo may be selected using the key 8.

Alternatively, if the program content is an 'rV signal, a line rotation method may be used.

Next, the output of the second code generator C-off is set for a long period of time compared to the change period of the output of the first code generator C-off. For example, the amount is changed on a monthly basis. Therefore, the key is changed over a long period of time.

The contents of the individual (- file (47>) are the contents of the receiving station B31 (
For subscription@), 161 constant is sufficient. However, subscribers:
Normally, the condition is that there is a relationship between transmission turbidity and one return.
, for example, only for subscribers who have also signed a contract.
All you have to do is record the information and delete the information for subscribers whose contracts have expired. This individual key is also called a keyword.

As is clear from the above explanation, this embodiment uses three-layer keys, and the characteristics of these keys are as follows.

The change period is short, long, and fixed.

In particular, it is necessary to use the keys Ks and K in a stacked manner, and changing the former in a short period increases security, while changing the latter in a long period facilitates system operation. In other words, when encrypting short-cycle -Ks and distributing it to each recipient, the key Ks is shared by a common /a
K and sends the same signal to all receivers. Therefore, distribution of 8 keys can be realized quite easily. Moreover,
In order to decrypt the key Ks, a long-period uK is required.
Since the key K is distributed to the station Cl31, security is maintained, and at the same time, even if this key K is encrypted and sent to each receiving station (331m), the change cycle of 'aK is long, so the key K is distributed to the receiving station C33.
, it can be easily realized regardless of the number.

In this way, it is important for system operation that the key K, which must be sent individually in different signal formats, has a long period, and since this uK specifies the encryption of the key Ks, the key Ks Frequent changes are possible.

Furthermore, the important afx points for the operation of this system are the three keys Ks and the signal amount (number of bits) of KM.

When looking at this from the viewpoint of transmission amount, it is preferable that the key Ks can be updated frequently, and it is necessary to send it to all recipients each time. Therefore, it is meaningless to increase the number of bits of the key Ks accordingly, and from the viewpoint of confidentiality, shortening the update cycle does not depend on the number of bits.

A sufficient effect can be obtained.

This becomes clearer when considering keys K and KM.

As is clear from the above description, the update cycle of the key KM is longer than the update cycle of the key Ks. In other words, since the key is only transmitted occasionally, there is no concern for the system in terms of transmission capacity even if the number of bits is increased. Since the key current is fixed, no matter how long it is, it will not interfere with system operation. Moreover, the key and KM are stored in a location that is difficult for recipients to access (for example, due to the structure of the terminal, the storage location for KM, etc. is sealed), but the number of bits is stored in such a location. Since more keys are stored, the security of the system will be much higher.

That is, by setting the number of bits of KM to be larger in order for the three keys Ks, the amount of transmission for the system is reduced and security is increased.

[Other embodiments of the invention]

Next, another embodiment will be described based on FIG.

This embodiment is roughly the same as the previous embodiment, except that the scrambler C inputs the three keys Ks to the first encryptor θ value t.
The point is that the output of the Bl code generator (3η output, and the first code generator 07) is transmitted to each receiving station along with a scrambled signal via the multiplexer (43).

For scrambler G, the output of g1's code generator (30) and the output of tgl's encoder OI have the same characteristics, fv, and if they are digital pit strings that are changed at a predetermined timing. good.

However, due to this change, on the receiving station (c) side,
In place of the first decoder 53) in the above-described embodiment, a third encoder 6η having the same capability as the first encoder 0 in the transmitting station 01) is prepared. With the above configuration, it is possible to achieve the same effects and operations as those of the embodiments described above.

[Other embodiments of the invention]

Next, another embodiment will be described using FIG. 5. This embodiment relates to broadcasting using PCM audio.

PCM audio is transmitted from the broadcasting station (611) to a plurality of terminals. A PCM signal is supplied from a PcM audio source (not shown) to the scrambler (1;0.
(Configuration G' of the plow - an example will be described later. Scrambler (65
) Specify the data conversion algorithm (using this as the key 8
) is a random number generator ((the output of the phrase). This random number generator (6') may be a well-known type, and may be one that generates random data of 2. However, in reality, the random number generator The output of the generator (67) is also not used as the key Ks as it is, but is passed through the first encoder and converted into data as the key Ks.

The first encoders (6) convert the input signal according to a conversion algorithm specified by a key Ki. This key Ki uses a tier key corresponding to a tier code. Here, tier is a station and a program. It is specified as a category and is a contract unit for viewing by the receiver.An example of a contract using tiers will be explained using Tables 7a1 to 3.

Table 2 Table 3 For example, if you want to watch sports programs from all stations, specify the tier marked with a circle as shown in Table 1. Also, if you want to watch all channel 40 programs, please watch the 2nd channel.
Specify as shown in the table. The designations of a news program on channel 1, a cultural program on channel 3, and a sports program on channel 4 are made as shown in Table 3. Here, a consecutive number is assigned to a program as a tier code. Then, depending on the contract, a tear coat ° will be given to the contracting party. Management information regarding this contract is stored in the contract file memory. The contents of this personal memory include the ID number assigned to each subscriber, all tier codes for programs for which valid viewing applications have been made, and the number n of tier codes.

For example, a subscriber with ID number 1 has tier code TitT2.
If there is a contract for viewing 0 programs, the contents of the contract file memory (7t) are (ID=L, n=2).

Tl, T2). This is set for all subscribers.

Such a tier code Ti is assigned to a program as described above, is supplied from the sound source together with the PCM audio, and is supplied as the address of the tier key file (731). For tier code Ti, tier key Ki
is memorized. For example, the tier code Ti may be set as a consecutive number for all programs and updated monthly. Furthermore, the correspondence between tier codes and tier keys may be changed at any time.

On the other hand, the output of the random number generator (6η) is supplied to the multiplexer (Y5) together with the scrambled signal. Furthermore, the tier key Kl is encrypted as follows.

That is, referring to the contents of the contract file memory (7υ), the tier code Ti is read out under a specific ID number, and then the tier code Ti is read out from the storage contents of the tier key file (t→) under the control of the reading device (7υ). Read the tier O key Ki corresponding to the tier code T1.Next, enter the specific ID number in the 4161 separate key file (7η is the cornerstone M, and I
The D number is used as the address input, and the individual keys of each contractor are stored in the corresponding address.

Therefore, an individual key KMn corresponding to a specific ID number is output from the individual key file (7η, and using this key circle n, the tier key Kl is encrypted by the second encryptor glue. ID The number is read from the contract file and provided to the packetizer.

The output of the multiplexer Ut5) is radiated as radio waves by a transmitter (not shown). As shown in FIGS. 6 and 7, the signal format used in this case is the audio signal format for satellite broadcasting determined by the Radio Technology Council, and includes A mode and B mode.

In both modes, 2048 bits form one frame with a period of 1 ms. The frame structure of Masu A mode is the 6th
As shown in the figure, a 16-pit frame synchronization signal (to), a control signal (8 inputs, 32-bit range bit 939
), channel 10 x 32 bit audio (911° (嘗, L!J5), +97) channel 480 bit independent data end, 7 x 32 bit error correction code (10
Consists of 1). Similarly, in B mode, a 16-pit frame synchronization signal (103), a control signal (105), a range bit (107), independent data (109), 2 channels of audio (111) with 48 bits per channel, 2
It consists of 24-bit independent data (113) and a 7×32-bit error correction code (115).

In the above frame structure, the scramble signal is the audio f9
1), +931, (9 warm, (971, t99
! , (111). Then, as independent data, the aforementioned various data are assigned to independent data +9' (109) and (113) in the following format. First, in response to full-power Φ entry, the tier code Ti corresponding to the program currently being transmitted, the random number R at that time, and a reset bit to be described later are constantly transmitted during the broadcast. In contrast, the delivery of the tier key Kl is done individually and in long spans. That is, as shown in FIG. 9, the delivery code is the contract code, the ID number for the subscriber, the number of tier codes (the number of programs applied for), the Ti for which the application was made, the corresponding 1, and r- ) are the encrypted signals in those formants.

Such a shipping code can be sent at the time of signing the contract.

Moreover, if the tier code is changed monthly, the tier code becomes valid (the contract becomes valid) on the 1st month of the previous month.
It is sufficient to deliver the product to the subscriber within a period of 30 days.

Even so, the security of this system remains high, as will be described later.

In this way, information is transmitted as radio waves from the broadcasting station (61) and received by each terminal. Then, the separation device (117) extracts the audio (9υ, (93), 6a, t97) from the frame-formed data without being separated.
), (118) are separated into a common code, shown in FIG. 8, and a delivery code, shown in FIG. 9. This is easily accomplished by establishing synchronization.

Audio (91), (!1131, (951, (9
7) and (111) are assigned a scramble signal, and are supplied to disk lamp 17 (119). The common code is stored in memory (121).

The delivery code is compared with the ID number set for each terminal, and only those with the same ID number are selected.
J (123). That is, this memo IJ
The contents of (123) are different for each subscriber, and the tier code T1 for a valid contract made by the subscriber with the terminal and the encrypted data for the tier code Ti are stored. Ru. here,
Even if someone else obtained this data, it would be of no use.

Next, the T1 stored in the memo') (121) is read out, which corresponds to the program currently being received.

It is checked whether this tier code Ti exists in the stored contents of the memory (123). If the same tier code Ti exists, it is confirmed that the subscriber has applied for the currently received band. This memo IJ (123) which is paired with STi at the same time
The contents of are read out and supplied to the first encoder (125).

The first decoder (125) corresponds to the second encryptor (18I), and the same key specifies the inverse transformation algorithm. In the terminal unit 3), the individual key KM11 is written in the ROM (127).1. This is then used as the key for the first decryptor (125).

Therefore, the output of the first decoder (125) becomes the key Ki. This key Ki is used as the key for the third encoder (129). At the same time, the input to this encoder (129) is the random number data stored in the memo IJ (121).

Therefore, the input of the third encoder (129) and the older one are
The input and key of the encoder (b9) are the same, and the first and third encoders (691, (129)) have the same configuration, so the same input and key are used between the broadcasting station Yu1 and the terminal (631). A key Ks is obtained.

When this key Ks is supplied as a key to the descrambler (119), 1) the CM double signal scramble is solved and the original PCM (signature) is obtained. This PCM signal is transmitted to the playback device (
(not shown), making it possible to enjoy broadcasting.

Next, specific examples of the scrambler and descrambler (119) will be explained. Here, we will explain a concrete example that is simpler than following DES.

The scrambler (I; ■ is, as shown in Figure 814,
Shift register (301) and nonlinear logic (3o3)
It consists of More specifically, the shift register (301
), when a program is started (when a program is changed), the reset bit switch (305) is designated and a digital signal serving as a key Ks is sequentially stored σ in the shift register 30+. Once all the keys Ks have been stored in the IC, the switch (305) is turned over and the contents of the shift register (301) are sequentially cycled in accordance with the clock signal.

However, by taking the exclusive OR of data at multiple predetermined locations in the shift register (301), the shift register (3i) 1
) of ν [new input.

Furthermore, a logical operation is performed on the contents of the shift register (3o1) using a nonlinear gate (303). In other words, the nonlinear logic (3++3) consists of a plurality of AND circuits and an exclusive OR circuit, and a shift register (
301) and performs an AND operation on these results. How to take the and is 1
For example, the M-series theory can be followed.

Exclusive OR of the output data of the nonlinear logic (303) obtained in this way and the original PCM signal.

Scrambling the signal is accomplished by the circuit (307). The configuration of the descrambler (119) is exactly the same, and the input of the circuit (307) is
The point is that it is not an M signal but a scrambled signal.

Here, the reset bit will be further explained.

The reset bit is used to synchronize the scrambler Kasumi and the descrambler (119). In other words, every time a reset bit is received, the shift register (301
)l/(:, a digital signal representing the key Ks is supplied.As mentioned above, since one frame has a period of 1ms, the period of 1m
A reset bit is supplied to the terminal (6 folds) every s, and the contents of the shift register (301) become the key Ks.

As a result, even if turning on the switch in the terminal bag has no relation to the progress of the program, the scrambler 9 and descrambler 119 will be in the same state, and the terminal 631 will be in the correct state. I get a signal.

In this way, since the reset bit is constantly supplied to the terminal in the form of a common code, operation at the terminal becomes extremely easy and reliable.

Furthermore, in this embodiment, kl# is changed to 8 by a tier code, but this tier code refers to the signal to be transmitted (
An attribute signal representing the content of a program signal (program signal), and generally may be an attribute unrelated to a tier. However, as will be described later, when managing viewing information, it is advisable to associate it with tiers.

[Other embodiments of the invention]

Next, an embodiment of the present invention will be explained according to the diagram.

This embodiment relates to pay television using two-way CATV.

First, the concept of this embodiment will be explained. Receivers are mass-produced by many manufacturers. Therefore, it seems difficult to keep the receiver design itself secret. Therefore, in this embodiment, the configuration of the receiver is considered to be made public. Instead, security is ensured by keeping the digital information (key) necessary to descramble the TV signal secret. Here, it is assumed that the receiver is handed over to the subscriber as a lease from the broadcasting station. The broadcasting station sets the above-mentioned key in the receiver before lending the receiver to the subscriber.

First, the broadcasting station side (211) will be explained. In this embodiment, the key to the scrambler is obtained by converting a program code that specifies a program (this is considered to be a physical code for a broadcast signal). That is, the program code is supplied to the encoder I2, and its output Ks is used as the scrambler key. In the scrambler (213), the TV signal is keyed to Ks.
Encrypt according to the conversion algorithm specified by This encrypted signal is synthesized with one program code by a synthesis circuit (226), and then is synthesized by a converter (241).
) is lifted onto the carrier band and transmitted.

The transmitted signal is sent to a receiving device (215) via a cable.
). The supplied signal is first passed through the converter (
242), the signal is returned to the baseband signal, and then the separation circuit (
228), the signals are separated into TV signals and program codes.

The program code is supplied to the encoder (239) via the viewing switch (254). Since this encoder (239) is the same device as the encoder (229) on the broadcasting station side, the output of the encoder is the same kg as on the broadcasting station side. The descrambler (217) returns the scrambled 9'■ signal to the original TV im code according to the inverse conversion algorithm specified by this key Ks. The W signal is supplied to a normal playback device.

The viewing switch (254) is used by the viewer to select viewing of the program. By turning on the viewing switch, the program code is supplied to the encoder (239) for the first time, making it possible to view two programs. At the same time, the program code is a viewing memo! J (245). The program code recorded in this viewing memory (245) represents the program code actually viewed, that is, viewing information. The viewing switch is provided on the front of the decoder as shown in FIG.

Viewers press this button when viewing a broadcast program.

The key contained in the key memo') (244) is the aforementioned private key. The broadcasting station stores the broadcasting station's key memo I in this key memory.
After setting the same key K as J (252), it is lent to the subscriber. As a result, for the first time, the encrypters (239) and (229) on the receiving side and the transmitter operate in the same way. As a result, the descrambler (217) performs the correct descrambler operation.

On the other hand, a counterfeit receiver does not have this private key and will not operate correctly. In this way, the design of the receiver can be made public, but even the key can be kept secret.

This guarantees that wiretapping can be prevented. It goes without saying that the casing of the receiver must have a sealed structure to prevent the secret key from being stolen from inside the decoder.

Next, a method of sending the viewing information stored in the viewing memory (245) of each receiver (215) to the broadcast station will be explained.

Basically, viewing information is also electrically transmitted to the broadcasting station via cable. First, the viewing information in the viewing memory (245) is encrypted by an encoder (246) using the secret key K as a key. This information is modulated by a modem (247), then transferred to a carrier band by a converter (248), and sent to the broadcasting station (211) through a specific channel shown in FIG.

On the broadcasting station (211) side, after restoring to binary information using a converter (249) and modem (250), the original viewing information is obtained using a decoder (251) using the secret key K as a key.

This is supplied to the charge calculation system (253) to calculate charges for each subscriber. At this time, the fee calculation method may be set for each program or for all programs.

Next, each part will be briefly explained. Encryptor (229
), (239) are, for example, the US data encryption standard (Da
It is sufficient to use an encoder according to the algorithm of TA f2 encryption 5 standard). ' The scrambler (213) may be one that replaces the II order of the scanning lines when the 1'V@ signal is a conventional analog signal and is a human input signal. The order of this replacement is specified by the key Ks.

The compositing circuit (226) is one that inserts a digital signal such as a program code into the output of the screen 9 (213) using a vertical retrace interval, as in teletext broadcasting.

Moreover, the configuration of each part may be arbitrary without departing from the spirit of the present invention, regardless of the above description.

[Other embodiments of the invention]

In the future, paid broadcasting using the satellite broadcasting direct reception system is expected to be implemented. In this case, since the satellite broadcasting medium is a one-way passageway, viewing information cannot be fed back. Therefore, an embodiment will be described in which viewing information is transmitted by direct communication.

Examples will be explained below. The parts other than the transmission of viewing information are the same as in the above-mentioned embodiment, so no special explanation will be given. Viewing memory (245) I'i's viewing information is kept secret as in the previous embodiment! It is encrypted by an encoder using aK as a key. After that, the acoustic converter (257) and the telephone (256)
) connected to the public network 1d telephone line. Broadcasting station (2
On the 11) side, there is a 4-speaker (258), an acoustic converter (25)
9) After being restored to binary information by K, the original viewing information is obtained by a decoder (251) using the secret key K as a key. This is supplied to the charge calculation system (253) to calculate charges for each subscriber.

In addition to telephone calls, there are other methods such as recording viewing information on a magnetic card or IC card and mailing it to broadcast station 9111.
The invention can be applied without departing from the spirit of the invention.

Furthermore, when the transmission signal is a television signal, the scrambler changes the transmission 11N order in units of scanning lines.
A descrambler may also be configured. At this time, the key information (
Ks) specifies this transmission order.

If the signal to be transmitted is a digital signal,
The descrambler may be formed from an M-sequence generator, a binary sequence from the M-sequence generator, and an exclusive logic circuit for the input digital signal 48.

At this time, the key information (Ks) is used as an initial value of the M sequence generator.

The key may also be transmitted in the same signal form as the scramble signal, but it may also be transmitted using the public telephone network, for example. Furthermore, a storage means using a magnetic material, such as a (-ki card) may be used.Furthermore, an IC card or the like in which a CDU memory is provided may be used.

In addition, the iKs decrypted by each receiving terminal is the key Ks of the transmitting side.
does not have to be exactly the same. That is, if the node design of the scrambler and descrambler is as shown in Figure g14, in order to obtain a correct program signal,
It is sufficient that the bit contents of the shift registers are set to be the same, and it is not necessary that the keys to be transmitted be filled with the same number 8. For example, the digital signal to be decoded by the descrambler may be obtained by subtracting a predetermined binary number from Ks, as long as a signal corresponding to the key Ks is obtained.

In this way, any modification within t151 that does not depart from the spirit of the present invention is of no effort, and all such modifications are included in the present invention.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing conventional examples, and Figures 3 to 1.
4 relates to an embodiment of the present invention, FIGS. 3 and 4 are diagrams showing the configuration of the basic embodiment, FIG. 5 is a diagram showing the configuration of the embodiment applied to PCM broadcasting, and FIG. Figures 6 to 9 are diagrams showing the structure of the take format, and Figure 10 is
Figures 11 and 12 are diagrams showing the configuration of an actual example of two-way paid broadcasting, and Figures 11 and 12 are diagrams for explaining the embodiment shown in Figure 10. Figure 13 is a diagram showing the configuration of an actual example of two-way pay broadcasting. FIG. 14, which is a diagram showing the configuration of an embodiment for pay broadcasting, is a diagram showing the specific configuration of the scrambler and descrambler in FIG. 5. (9...Scrambler, 137)...First code generator, (Ull...First encoder, 140...Second code generator, (451...Second code generator) 2 encoder, (471...individual pure file, 61)...descrambler, C current...first decoder, 155)...second decoder, 57)...th 3 cipher. Agent Patent Attorney Rules Noriyuki Chika 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 0 Figure 7 Figure 9 Figure 111a Figure 12 Figure 14

Claims (5)

[Claims] (1) A first (i) converting means for converting a significant signal from a signal source according to a first algorithm;
a first means for transmitting a signal from the signal converting means to a plurality of receiving means; and a second 1h symbol for converting the signal into the significant IB- symbol after receiving the A symbol from the means. 4!3 signal conversion means for converting the first key information specifying the first algorithm according to the second algorithm; and the third signal conversion means. Specify the second algorithm of → t2 key 1^ to 4th (H conversion means, and the outputs of the 01J third and fourth No. 16 conversion means, respectively) A second means for distributing the output to the receiving means and a fourth signal converting means sent by this means to obtain information corresponding to the second key information according to an algorithm corresponding to the algorithm of note 'J43. gl!50 information converting means and the information obtained by the fifth signal converting means to obtain information corresponding to the first torque information from the output of the third signal converting means.
116 No. 16 converting means, and the second equal sign converting means is operated by the axis obtained by the sixth signal converting means. (2) The transmission method according to claim 1, wherein the amount of information of the first key information is smaller than the amount of information t of the second key information. (3) The transmission system according to claim 1, characterized in that third key information specifying the third algorithm is also set in the receiving means. (4) First. Second. 2. The transmission system according to claim 1, wherein the number of third key 11 reports (t-information) is set to be large in this order of 10. (5) The second means is 15. 3. The transmission system according to claim 1, further comprising third and fourth means for independently distributing the outputs of the ÷3 and fourth signal converting means. t6) The transmission system according to claim 5, wherein the first and third means use the same communication medium. (The transmission system according to claim 5, wherein the first to third power ratio means use the same communication medium.