JP2001211127A - Scramble control method for digital broadcast - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple scramble control technology which is different from conventional technology. SOLUTION: An unciphered scramble flag for showing whether or not a specific program of a digital broadcast is scrambled is included in scramble key data including a ciphered scramble key for the specific program.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a scramble control technique in digital broadcasting.

[0002]

2. Description of the Related Art In recent years, with the development of computer technology, image / audio technology using digital signals has become widespread. In addition, instead of the conventional analog television broadcasting, digital broadcasting is spreading all over the world.

[0003] In paid digital broadcasting, scrambled (encrypted) broadcasting is usually performed in order to allow a viewer to view only programs that have been subscribed in advance. Several methods are used as the scramble control method. For example, in a certain broadcast system using the MPEG system (hereinafter, referred to as “broadcast system A”), a transmitting device sets a bit indicating whether or not scrambling is performed for each transport packet as one unit of transmission. I do.
Then, the receiver controls the scrambling by reading the scramble control bit in each transport packet.

[0004]

However, since one transport packet is small data of about 200 bytes, there has been a problem that the receiving apparatus must frequently judge the scramble state.

Further, in another broadcasting system (hereinafter referred to as "broadcasting system B"), a scramble control method different from the broadcasting system A is adopted, but this method has a problem that it is considerably complicated. .

[0006] The present invention has been made to solve the above-mentioned problems in the prior art, and an object of the present invention is to provide a scrambling control technique with high processing efficiency for a receiver or a transmitter.

[0007]

SUMMARY OF THE INVENTION In order to solve at least a part of the above-mentioned problems, the present invention provides scramble key data including an encrypted scramble key for a specific program of digital broadcasting. Contains an unencrypted scramble flag for indicating whether or not a specific program is scrambled.

In this way, it is possible to easily determine the presence or absence of scrambling only by reading the unencrypted scramble flag contained in the scramble key data.

[0009] When a digital broadcast is transmitted by a transmission packet, which is one unit of transmission, the scramble key data is not included in all transmission packets, but is included only in some transmission packets. It may be made to be.

Thus, when the scramble flag indicates that there is no scramble, the receiving device can receive the program without checking the scramble state of the transmission packet. That is, the receiving device does not need to always determine whether or not scrambling is performed for all transmission packets, so that the load on the receiving device can be reduced.

[0011] The scramble key data may be transmitted a plurality of times during the broadcasting of a specific program. At this time, it is preferable that the value of the scramble flag can be changed every time the scramble key data is transmitted.

This makes it possible to easily change the scramble state even during the same program.

The present invention provides a scramble control method,
Digital broadcasting system, transmitting apparatus and receiving apparatus for digital broadcasting system, transmitting method and receiving method, computer program for realizing the functions of those methods and apparatuses, recording medium storing the computer program, and computer program It can be implemented in various ways, such as a data signal embodied in a subcarrier.

[0014]

DETAILED DESCRIPTION OF THE INVENTION Configuration of Digital Broadcasting System: Hereinafter, embodiments of the present invention will be described based on examples. FIG. 1 is a block diagram showing a configuration of a digital broadcasting system as one embodiment of the present invention. This digital broadcasting system includes a transmitting device 100 and a receiving device 200
, A satellite 300, and a key / customer management system 400. As the satellite 300, a broadcasting satellite BS, a communication satellite CS, or the like can be used. From the transmitting device 100,
Satellite 3 via transmitting antenna 110 (transponder)
At 00, digital broadcast data is transmitted. On the other hand, the receiving device 200 receives the digital broadcast data supplied from the satellite 300 via the receiving antenna 210. In addition,
There are a plurality of transmitting devices 100 and a plurality of receiving devices 200, respectively. This digital broadcasting system broadcasts according to the MPEG system.

An IC card is distributed to the viewers holding the receiving device 200 in advance, and a key (or a key algorithm) for descrambling the digital broadcast data is stored in the IC card. I have. The receiving device 200 uses the key to release the scramble set in the digital broadcast data. The record of viewing by the viewer is transferred to the key / customer management system 400 via, for example, a telephone line. The setting of a scramble key for digital broadcast data in transmitting apparatus 100 is also performed by using a key / key.
This is performed based on information supplied from the customer management system 400.

FIG. 2 is an explanatory diagram showing the structure of data in the MPEG system. NIT shown in FIG.
(Network Information Table)
6 is a table showing the correspondence between transponders (satellite repeaters) and program identification numbers (hereinafter, referred to as “program IDs”). Usually, a plurality of programs are transmitted from one transponder via a plurality of channels. In this specification, a “program” is one unit of a broadcast service supplied from one channel, and is usually a broadcast service supplied over a certain period of time (for example, 1 to 2 hours). Means content.

The PAT shown in FIGS. 2 (b-1) and 2 (b-2)
The (program association table) includes a program ID, which is an identifier of a plurality of programs supplied from one transponder, and a PID shown in FIGS. 2 (c-1) and 2 (c-2).
MT (program map table) packet ID
It is a table which shows the correspondence with (PID). Here, the “packet ID” means an identifier assigned to a transport packet, which is one unit of transmission.

The PMT shown in FIGS. 2 (c-1) and (c-2)
The (program map table) is a table showing the correspondence between various data (video, audio, etc.) constituting one program and their packet IDs.
Data constituting one program includes a video stream shown in FIG. 2 (d-1), an audio stream shown in FIG. 2 (d-2), and an ECM (entitlement shown in FIG. 2 (d-3)). Control message). The ECM corresponds to scramble key data including an encrypted scramble key, as described later.
As shown in FIG. 2 (c-2), for a program not scrambled through the program, the ECM
Is registered in the PMT.

When a program is selected by the viewer, the receiving apparatus 200 refers to the PAT (FIG. 2 (b-1)),
The PMT packet ID for the selected program is obtained. However, when the selected program is not included in the PAT, the receiving apparatus 200 sets the NIT (FIG. 2).
Referring to (a)), the receiving frequency band is switched to the frequency band of the transponder supplying the selected program, and a new PAT is received. Upon receiving the packet ID of the PMT from the PAT, the receiving device 200
To receive the PMT (FIG. 2 (c-1)). Further, by referring to the PMT, a video stream, an audio stream, and an ECM packet ID constituting the program are acquired. Then, a transport packet of each data constituting the program is received using these packet IDs.

FIG. 3 is an explanatory diagram showing packetization of data in the MPEG system. In the left end of FIG.
And a PAT for one transponder and this PA
PMT regarding three programs included in T (PMT1 to PMT
MT3) and the names of elementary streams ES (ES1a to ES4b) constituting the three programs are arranged. Here, the “elementary stream” means a video stream and an audio stream, and means “data indicating substantial contents of a program”. The thickness of the hatched bar drawn on the right side of each data name in FIG. 3 qualitatively indicates the data amount of each data. That is, the elementary stream has a relatively large data amount, and the other data has a relatively small data amount.

Incidentally, it is possible to constitute the contents of one program by a plurality of video streams and a plurality of audio streams. For example, the third program
It can be composed of two video streams ES3a and ES4a and two audio streams ES3b and ES4b.

These various data are packetized, multiplexed and transmitted. For example, from time t1
During the period of t2, various data shown in FIG. 3 are packetized and transmitted. However, as shown in the lower part of FIG. 3, the data other than the elementary stream has a small data amount, and thus is transmitted at a considerably low frequency. For example, NIT is transmitted about once every one second, and PAT, PMT, and ECM are each transmitted for about 100 ms.
Sent once every time.

FIG. 4 is an explanatory diagram showing an example of an arrangement of transport packets. One transport packet is composed of a header and a payload.
It has a length of bytes. "Payload" refers to the data portion to be transmitted. Various data shown in FIGS. 2 and 3 are stored in the payload portion and transmitted. However, in one transport packet,
Different types of data are not stored. In the example of FIG. 4, NIT is stored in the first packet,
The second and third packets store the elementary stream ES1a, and the fourth packet stores the elementary stream ES1b.

As shown in the lower part of FIG. 4, a PID (packet ID) is set in the header of each transport packet. The receiving device 200 is a PAT (FIG. 2 (b-
1)) or PMT registered in PMT (Fig. 2 (c-1)).
From the ID, the contents of each packet are identified.

In the header of the transport packet, a 2-bit scramble control bit SCbit is further set. SCbit = “00” means that there is no scramble key (that is, not scrambled). SCbit = "10" is EVEN in the ECM.
Means that it is scrambled using the key,
Cbit = “11” means scrambled using the ODD key. Both the EVEN key and the ODD key are scramble keys, and are usually about 20 to 30.
The EVEN key and the ODD key are used alternately every second. EC
The manner of transmission of the scramble key by M will be described later.

In the conventional broadcast system A, scramble control is performed by setting a scramble control bit SCbit for each transport packet. By the way, the transport packet is a short packet of 188 bytes, and is transmitted, for example, approximately once every 0.4 ms at a transmission speed of 4 Mbps. If the receiving apparatus 200 must always determine the presence or absence of scrambling for each transport packet at such a frequency, a considerable load is placed on the receiving apparatus 200. Therefore, in the present embodiment, as described below, the data structure in the ECM is devised so that it is not necessary to always determine the presence or absence of scrambling for each transport packet.

FIG. 5 is an explanatory diagram showing the configuration of the ECM in this embodiment. The ECM has a section header, a data portion including an encrypted scramble key, and a cyclic redundancy check bit (CRC). EC like this
The entirety of M is stored and transmitted in the payload section (FIG. 4) of one transport packet.

The data portion contains two scramble keys, a current key (a key currently used) and a next key (a key to be used next), in an encrypted form. There are two types of keys, an EVEN key and an ODD key.
The EVEN key and the ODD key are normally alternately switched about every 20 to 30 seconds. Therefore, if the current key is EVEN
When it is a key, the next key is an ODD key. Conversely,
When the current key is an ODD key, the next key is E
VEN key. Which of the EVEN key and the ODD key is used is specified by the value of the scramble control bit SCbit (FIG. 4) in each transport packet.

The reason that the ECM includes both the current key and the next key is to reduce the time during which the receiving apparatus 200 cannot view the data due to the processing of the ECM. That is,
If both the current key and the next key are stored in the receiving device 200, the next key can be used immediately when the key is switched in the same program. Further, when the viewer changes the channel, the viewing can be performed by using the current key included in the ECM of the program.

The receiving device 200 is an IC held by the viewer.
The encrypted scramble key is decrypted using the key stored in the card. In addition, the receiving apparatus 200 descrambles (descrambles) the digital broadcast using the decrypted scramble key. Like a key stored in this IC card, a key for decrypting an encrypted scramble key (hereinafter, referred to as a “viewer key”)
Is distributed to viewers who are authorized to receive a particular program. Here, the viewer has "authority to receive a specific program"
In order to acquire the service, it is common to conclude a contract for transmitting and receiving a pay broadcast.

At the head of the data part of the ECM, an unencrypted scramble flag SF is registered. The scramble flag SF indicates whether or not the program is currently scrambled. That is, when the value of the scramble flag SF is 0, the program is not scrambled, and when the value is 1, the program is not scrambled. When the value of the scramble flag SF is 0 (non-scramble), the encrypted scramble key may not be registered in the data section of the ECM.

Since the scramble flag SF is not encrypted, the receiver 2 of the viewer who does not have the viewer key
Even at 00, the value of the scramble flag SF can be obtained. Therefore, programs that are not scrambled
A viewer who does not have a viewer key can also view. Note that the unencrypted scramble flag S
F may be registered in the section header (for example, table_id_extension part), not in the data part.

B. FIG. 6 is a block diagram showing the configuration of the transmitting apparatus 100. The control data generator 120 generates data other than the ECM and the elementary stream (that is, NIT, PAT, and PMT). The video encoder 122 generates a video stream by encoding the video data in the MPEG format, and the audio encoder 124 generates an audio stream by encoding the audio data in the MPEG format. The ECM generation unit 126 generates the ECM shown in FIG.

The various data thus created are multiplexed by the multiplexing unit 130 and further scrambled by the scrambler 140 as needed. When scrambling a program, the scramble control unit 160 controls the scrambler 140 and the ECM generation unit 126.
That is, when scrambling, the ECM generation unit 126 stores the encrypted scramble key in the ECM (FIG. 5) and sets the value of the scramble flag SF to 1. The various data scrambled in this way are modulated by the modulator 150 and transmitted. on the other hand,
If no scrambling is performed, the ECM generation unit 126
The value of the scramble flag SF is set to 0. At this time, the encrypted scramble key may or may not be registered in the data portion of the ECM.

FIG. 7 is an explanatory diagram showing a scrambling control method in the conventional broadcasting system B. FIG. 7A shows PM
T (FIGS. 2 (c-1) and (c-2)), and FIG.
Shows the current key and the next key of the ECM, and FIG. 7C shows the scramble control bits SC of the elementary stream.
The contents of each bit are shown. In the example of FIG. 7, it is assumed that a CM such as a program notice is inserted in a non-scrambled state during a period from time t1 to t3 in the middle of the program P1. ECM transmitted during time t2 to t3
However, the reason for including the ODD key (ODD1) as the next key is to enable the receiving device 200 to immediately release the scrambled state by using the ODD key after time t3.

In the conventional broadcasting system B, when it is desired to change the scramble state in the middle of the same program, it is necessary to change the PMT according to the scramble state of the program as shown in FIG. That is, the ECM packet ID is registered in the PMT in the scramble state, and the absence of the ECM is registered in the PMT in the non-scramble state. Therefore, when the scramble state is changed in the middle of the same program, the transmitting apparatus 100
Must be changed and sent. In the transmission device 100, the PMT is created by the control data generation unit 120, and the setting of the scramble state is controlled by the scramble control unit 160. Therefore, in order to change the PMT according to the scramble state, the control data generation unit 1
20 and the scramble control unit 160 need to cooperate to match the actual scramble state with the registered contents of the PMT.

FIG. 8 shows a scramble control method in the embodiment. The contents of the scramble key in FIG. 8B and the scramble control bit SCbit in FIG.
These are the same as those shown in FIGS. 7B and 7C, respectively. However, the lower part of FIG. 8B also shows the state of the scramble flag SF in the ECM. The scramble flag SF is set to off (no scramble) during the period from time t1 to t2, and is set to on (with scramble) from time t2 to t3. Actually, the general viewer who does not have the user key can view freely from time t1 ', at which time Ta has elapsed from time t1, to time t2', at which time Ta has elapsed from time t2. Here, the time Ta is a time required for receiving the ECM in the receiving device 200 and determining the scramble flag SF. As a result of the determination of the scramble flag SF, when it is determined that the mobile phone is in the scramble state, the ECM process (scramble key decryption process) is executed at a time Ta ′ after the time t2 ′. Normally, the sum of the time Ta required for determining the scramble flag SF and the time Ta ′ required for processing the ECM is approximately 200 to
It is 300 ms.

The length Tb of the period t2 to t3 (the period during which the next key ODD1 is transmitted by the ECM immediately before returning from the non-scramble state to the scramble state) is long enough to secure this processing time (Ta + Ta ′). It may be set to, for example, about 0.5 seconds. This makes it possible to shorten the length of the period t2 ′ to t3 during which the general viewer cannot view, to such an extent that there is practically no problem.

As shown in FIG. 8A, in the scramble control method of the embodiment, even when the scramble state is changed during the same program, the transmitting apparatus 100 does not need to change the PMT, and Scramble flag SF
Can be changed. Therefore, in the transmitting device 100,
The control data generator 120 does not need to change the PMT, and the scramble controller 160 can easily change the scramble state independently.

C. Configuration and operation of receiving apparatus: FIG. 9 is a block diagram showing the configuration of the receiving apparatus 200. Digital broadcast data received by the receiving antenna 210 is first demodulated by the demodulation unit 222. The error correction unit 224 performs an error correction process on the demodulated broadcast data. The broadcast data whose error has been corrected is descrambled by the descrambler 226 (scramble descrambler) as necessary. The broadcast data in which the scrambled state is released is separated by the transport decoder 228 into video data, audio data, and other data. The video data and the audio data are decoded by the video decoder 234 and the audio decoder 236, respectively. The decoded audio data is
It is supplied to a TV set 250 which is an audio output device. On the other hand, the decoded video data is transmitted to the CRT controller 2
The video signal is converted to a video signal suitable for the TV set 250 by 38 and supplied to the TV set 250.

Data other than video data and audio data (ie, NIT, PAT, PMT, ECM)
Is transferred from the transport decoder 228 to the memory 232 and stored. The CPU 230 has a memory 232
Of the receiving device 200 in accordance with the data stored in the.

The receiving device 200 further includes a remote control light receiving section 24 for receiving an optical signal from the viewer's remote control.
0, an operation panel 242 for the viewer to operate the receiving device 200, and a connector 244 to which the IC card 260 is connected.

FIG. 10 is a flowchart showing a procedure for receiving a program in digital broadcasting. When the viewer turns on the power of the receiving device 200 and selects a program, the receiving device 2
00 is the PAT in step T1 (FIG. 2 (b-
1)) is received. This PAT is stored in the memory 232 (FIG. 9). In step T2, the CPU 230 refers to this PAT and determines whether or not the selected program exists in the PAT. Since the PAT is created for each transponder, the process in step T2 is the same as determining whether the selected program is supplied from the transponder of the frequency band currently being received.
When the selected program exists in the PAT, the process shifts from step T2 to step T4. On the other hand, when the selected program does not exist in the PAT, the CPU 230
Switches the transponder with reference to the NIT (FIG. 2A) in step T3, and re-receives the PAT.
In the process of step T3, the NIT is stored in the memory 23.
If it is not stored in the second NIT, a new NIT is first received.

In step T4, the PM is referred to the PAT.
T (FIG. 2 (c-1)), and in step T5, P
The ECM (FIG. 5) is received with reference to the MT. These P
MT and ECM are also stored in the memory 232.

In step T6, CPU 230 determines whether or not the selected program is currently scrambled. Note that the method of determining whether or not scrambling is performed differs between the broadcasting method according to the embodiment and the conventional broadcasting method, which will be described later. If the program has not been scrambled, the process shifts to step T8 to receive the program. At this time, the descrambler 226 does not release the scramble, and the received data output from the error correction unit 224 is decoded by the decoders 234 and 236.

On the other hand, if the program is scrambled, the encrypted scramble key in the ECM is decrypted using the viewer key stored in the IC card 260 in step T7. The decryption of the scramble key is usually performed inside the IC card 260. When the decrypted scramble key is set in the descrambler 226, the descrambler 226 enters a state in which the descrambler of the program can be descrambled. Then, in step T8, receiving apparatus 200 receives the program and outputs images and sound to TV set 250.

FIG. 11 is a flowchart showing a detailed procedure of steps T6 to T8 in the conventional broadcasting system A. In step T10, the value of the scramble control bit SCbit (FIG. 4) of each transport packet is checked. This step T10 is processing corresponding to step T6 in FIG. 8, and is executed as interrupt processing of the CPU 230 when each transport packet is received. When the value of the scramble control bit SCbit is "10" or "11", the program has been scrambled, so that the IC card 260
It is determined whether or not (FIG. 9) is inserted in receiving apparatus 200. When the IC card 260 is not inserted, the decoding in the receiving device 200 is stopped, and a predetermined abnormal display (for example, “Cannot view”) is displayed on the screen of the TV set 250.

On the other hand, when IC card 260 is inserted, ECM is received in step T13.
In step T14, the ECM is performed using the IC card 260.
, And the descrambler 226 performs the descrambling process using the decrypted key. In step T15, the decoder 228,
234 and 236 (FIG. 7) start decoding the elementary stream. When an abnormal display is displayed on the TV set, the display is cleared. Then, in step T8, the program is received and output on the TV set 250.

In step T10, when the value of the scramble control bit SCbit is "00", the program is not scrambled, so that the flow shifts to step T15 to immediately start decoding the elementary stream. Then, in step T8, the program is received and output on the TV set 250.

As described above, in the conventional broadcasting system A, every time the receiving apparatus 200 receives a transport packet, the processing of steps T10 to T15 must always be executed. I was

FIG. 12 is a flowchart showing a detailed procedure of steps T6 to T8 in the broadcasting system of the embodiment. Steps T11, T12, T15,
The processing of T8 is the same as the processing of these steps in FIG.

In step T20, step T5 (FIG. 1)
0), the scramble flag SF (FIG. 5) of the ECM received is checked. If the scramble flag SF indicates no scramble, the process proceeds to step T15, where the decoding of the elementary stream is started immediately, and the program is received in step T8. At this time,
Scramble control bit S in transport packet
Since there is no need to monitor Cbit, the load on the receiving device 200 is greatly reduced.

On the other hand, if the scramble flag SF indicates that scramble is present, it is determined whether or not the IC card 260 is inserted into the receiving device 200 in step T11. If the IC card 260 is not inserted, the decoding is stopped in step T12, and an abnormal display is made. On the other hand, IC card 2
When 60 is inserted, a descrambling process is executed in step T14 '. In this step T14 ', the scramble control bit SC in each transport packet is
The scramble key specified by bit is decrypted, and the descrambling process is performed using the decrypted key. Then, decoding is started in step T15, and the program is received in step T8.

As described above, in this embodiment, it is determined whether or not the selected program is currently scrambled by checking the unencrypted scramble flag SF registered in the ECM (FIG. 5). be able to. That is, by detecting a change in the scramble flag SF in the ECM at the time of reception, decoding /
It is possible to stop and set / cancel the abnormal display. Therefore, when the scramble flag SF indicates non-scramble, the scramble control bit S registered in the header of each transport packet is used.
There is no need to check Cbit (FIG. 4). For example, 4Mbps
At a transmission speed of, a transport packet is transmitted and received once every about 0.4 ms. If it is necessary to always determine whether or not scrambling is performed at such a frequency in the receiving apparatus 200, a considerable load is imposed on the receiving apparatus 200. On the other hand, ECM is only included in some transport packets,
It is only sent and received times. Therefore, if the scramble flag SF registered in the ECM is used,
When the elementary stream is in the non-scrambled state, the load on the receiving device 200 is greatly reduced.

As described above, in this embodiment, the scramble state can be arbitrarily changed every time the ECM is transmitted / received. Further, the transmitting device 100 and the receiving device 20
It is possible to easily change the scramble state without imposing an excessive load on 0.

D. Modifications: The present invention is not limited to the above-described examples and embodiments, and can be carried out in various modes without departing from the gist thereof. For example, the following modifications are also possible. is there.

D1. Modification Example 1 In the above-described embodiment, the digital broadcasting system using a wireless line using a satellite has been described. However, the present invention is also applicable to a digital broadcasting system using a terrestrial wave and a digital broadcasting system using a wired line. .

In the above embodiment, the digital broadcasting system using the MPEG system has been described.
The present invention can be used for digital broadcasting systems other than the MPEG system. That is, the present invention generally comprises:
The present invention can be applied to a digital broadcasting system using scramble key data used for transmitting an encrypted scramble key.

D2. Modification 2 In the above embodiment, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware. You may. For example, the transmitting device 10
0 (FIG. 6) and the functions of some hardware circuits of the receiving device 200 (FIG. 9) can be realized by a computer program.

Such a computer program is provided in a form recorded on a computer-readable recording medium such as a flexible disk or a CD-ROM. The computer constituting the transmitting device 100 and the receiving device 200 reads the computer program from the recording medium and stores the computer program in the internal storage device or the external storage device. When implementing the functions of a computer program,
A computer program stored in the internal storage device is executed by a microprocessor of the computer.

The “recording medium” in the present invention includes a flexible disk, a CD-ROM, a magneto-optical disk, an IC card, a ROM cartridge, a punch card, a printed matter on which a code such as a bar code is printed, and an internal storage of a computer. Device (RAM, ROM, etc.)
And various computer-readable media such as an external storage device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a digital broadcasting system as one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a data structure in an MPEG system.

FIG. 3 is an explanatory diagram showing packetization of data of the MPEG system.

FIG. 4 is an explanatory diagram showing an example of an arrangement of transport packets.

FIG. 5 is an explanatory diagram showing a configuration of an ECM in the embodiment.

FIG. 6 is a block diagram showing a configuration of a transmission device 100.

FIG. 7 is an explanatory diagram showing a conventional scrambling control method in broadcast system B.

FIG. 8 is an explanatory diagram showing a scramble control method in the embodiment.

FIG. 9 is a block diagram showing a configuration of a receiving device 200.

FIG. 10 is a flowchart showing a digital program receiving procedure.

FIG. 11 shows steps T6 to T in the conventional broadcasting system A.
8 is a flowchart showing the detailed procedure of FIG.

FIG. 12 is a flowchart showing a detailed procedure of steps T6 to T8 in the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 transmission device 110 transmission antenna 120 control data generation unit 122 video encoder 124 audio encoder 126 ECM generation unit 130 multiplexing unit 140 scrambler 150 modulation unit 160 scramble control unit 200 reception device 210 ... Reception antenna 222 ... Demodulation unit 224 ... Error correction unit 226 ... De-scrambler (descrambling unit) 228 ... Transport decoder 230 ... CPU 232 ... Memory 234 ... Video decoder 236 ... Audio decoder 238 ... CRT controller 240 ... Remote control light receiving Unit 242 operation panel 244 connector 250 TV set 260 IC card 300 satellite 400 key / customer management system

Claims (6)

[Claims] 1. A method for controlling the presence / absence of scrambling in a digital broadcast, comprising: determining whether the specific program is scrambled in scramble key data including an encrypted scramble key for the specific program in the digital broadcast. A scramble control method characterized by including an unencrypted scramble flag for indicating whether or not the scramble is performed. 2. The scramble control method according to claim 1, wherein the digital broadcast is transmitted by a transmission packet which is one unit of transmission, and the scramble key data is included in all transmission packets. And a scramble control method that is included only in some transmission packets. 3. The scramble control method according to claim 1, wherein the scramble key data is transmitted a plurality of times during the broadcast of the specific program, and the value of the scramble flag is determined by the scramble key data. A scrambling control method that can be changed each time it is transmitted. 4. A digital broadcasting system, comprising: a transmitting device that transmits a digital broadcast; and a receiving device that receives the digital broadcast, wherein the transmitting device is configured to encrypt a specific program of the digital broadcast. A digital broadcast system for transmitting scramble key data including an encrypted scramble key, including an unencrypted scramble flag for indicating whether or not the specific program is scrambled. 5. A transmission device for transmitting a digital broadcast, comprising: determining whether or not the specific program is scrambled in scramble key data including an encrypted scramble key for the specific program of the digital broadcast. A transmission device for transmitting a message including an unencrypted scramble flag for indicating whether or not the data has been encrypted. 6. A receiving apparatus for receiving a digital broadcast, comprising: a descrambling unit for descrambling received data of a digital broadcast in a descrambling state; a decoding unit for decoding the received data; A control unit for controlling a decryption unit and the decoding unit, the control unit, when receiving scramble key data including an encrypted scramble key for a specific program of the digital broadcast, Reading an unencrypted scramble flag from the scramble key data to indicate whether or not the specific program is scrambled, indicating that the specific program is not scrambled by the scramble flag The descrambling state is canceled by the descrambling unit. Receiving apparatus characterized by causing the decoding by the decoding unit without I.