JP2002084517A - Scrambling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that conventionally expensive and dedicated scrambling IC is required in scrambling processing. SOLUTION: Control bits simulating packets to be subjected to scramble- processing are raised in the headers of the respective packets, which is not subjected to scrambling of MPEG(moving picture expert group encoding system). The respective packets, where the control bits are raised are inputted to descramble IC, are subjected to descramble-processing and are scrambled. The control bits showing that the packets are scrambled are raised in the headers of the processed packets.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scrambling method for encrypting various information (data) such as video information, music information, and character information when transmitting the data. It can be used in various communication fields such as communication and CATV.

[0002]

2. Description of the Related Art A conventional scrambling method will be described by taking image information compressed by the MPEG2 system as an example. The image information (image information and audio information) is digitized by an MPEG encoder to become a packet stream (MPEG2TS) of MPEG2 transport packets in units of 188 bytes. MP
The EG2TS is input to a dedicated scrambler (dedicated scramble IC) as shown in FIG. 3, and is encrypted by the IC based on a predetermined key (each packet is scrambled). Note that a control bit indicating that the packet is encrypted is set in the header of each scrambled packet, and the descrambler (descramble IC) on the receiver side receives the control bit according to the control bit. It recognizes that the scrambled packet has been scrambled, and cancels the scramble. In addition, the key required for the descrambler to descramble is transmitted as one of the packets together with the image and music as the related information, but this is also scrambled, and the key for descrambling is It is stored in secret in an IC card inserted for each scrambler.

[0003]

SUMMARY OF THE INVENTION In information transmission,
Since information is transmitted from one or more transmitting stations to a large number of recipients, the amount of scramblers installed in the transmitting stations is smaller than that of descramblers installed in each receiver's house. Therefore, the scramble IC, which is a main part of the scrambler, is more expensive than the descramble IC, which is a main part of the descrambler, so that the price of the whole scrambler rises and the cost of the whole system also rises.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problem by scrambling using a descramble IC which is cheaper than a scramble IC.

According to the scrambling method of the present invention, a control bit for simulating a packet after being scrambled is set in a header of each packet which is not scrambled by the MPEG (moving picture coding system), and the control bit is set. Each of the packets is input to a descramble IC, descrambled and scrambled, and a control bit indicating that the scramble processing has been completed is set in the header of each processed packet.

[0006]

(Embodiment 1) A first embodiment of a scrambling method according to the present invention will be described with reference to FIG.
First, a control bit (scramble control bit) is set in the header of each unscrambled MPEG TS packet to simulate that the packet has been scrambled.

[0007] Next, the MPEG TS (packet) with the scramble control bit set is descrambled.
Enter C. The descramble IC determines whether or not the packet is scrambled based on the control bit set in the header of each packet,
It is designed to perform descrambling when scrambled, and to output without any processing when scrambled. Therefore, the input packet is not scrambled, but the descrambling IC is determined to be a scrambled packet because the scramble control bit indicating that scramble processing has been completed is set in the header. , And descrambles it based on the given key. As a result, the packet is scrambled.

[0008] Thereafter, a scramble control bit indicating that the packet has been scrambled is set in the header of each packet of the scrambled MPEG TS output from the descramble IC. That is, since the scramble control bit set before being input to the descramble IC has been lowered in accordance with the processing by the descramble IC, the descramble IC on the receiver side remains as it is in the input MPEG TS. Judge that the scramble has not been applied and do not perform the descrambling process. Therefore, a scramble control bit is set in order to avoid this and cause the descrambling IC on the receiver side to perform the usual descrambling process.
As described above, an MPEG TS that is exactly the same as the MPEG TS scrambled by the conventional scramble IC is generated.

As a circuit for implementing the scrambling method of the present invention, for example, a circuit as shown in FIG. 2 can be considered. The circuit shown in FIG. 2 sets a scramble control bit in each packet of the MPEG TS before the scramble process to simulate that the scramble process has been performed, and re-scrambles the scramble control bit in each packet after the scramble process in addition to the descramble IC 1. It comprises a logic IC (for example, a PLD) 2 for standing up and a key generation IC 3 for generating a key required when the descrambling IC 1 performs descrambling processing.

[0010]

The scramble method of the present invention has the following effects. (1) Inexpensive descramble IC compared to scramble IC
Can be used for scrambling, so that a system can be constructed at low cost. Therefore, it is suitable for a CATV system or the like in which a service area is narrower than that of a CS broadcast or the like, and it is difficult to spend much cost on facilities.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of a scrambling method according to the present invention.

FIG. 2 is a block diagram showing an example of a circuit for implementing the scrambling method of the present invention.

FIG. 3 is an explanatory diagram showing a conventional scrambling method.

[Explanation of symbols]

 1. Descramble IC 2. Logic IC 3. Key generation IC

Claims (1)

[Claims] 1. A control bit for simulating that a packet has been scrambled is set in a header of each packet that has not been scrambled by MPEG (moving picture coding system), and each packet in which the control bit is set is decoded. A scrambling method comprising: inputting a signal to a scramble IC; descrambling the data to be scrambled; and setting a control bit in the header of each processed packet to indicate that the packet has been scrambled.