KR20050021555A - Method of distributing encrypted portions of an audiovisual programme - Google Patents

Abstract

A method of distributing encrypted portions of an audiovisual program to user terminals T1 and T2, wherein successive portions of the program are encrypted using different keys, and the method comprises a telephone call with the call center 4 from the user terminal. At the start of the communication, transmitting the key as a sequence from the call center to the user terminal during telephone communication is done in a manner synchronous with the distribution of consecutive encrypted portions of the program.

Description

Distribution method of encrypted portions of an audiovisual program {METHOD OF DISTRIBUTING ENCRYPTED PORTIONS OF AN AUDIOVISUAL PROGRAMME}

The present invention relates to a method for distributing encrypted portions of an audiovisual program to a user terminal, and more particularly, to a television receiver decoder, wherein successive portions of the program utilize different keys before being distributed to the user terminal. Is encrypted.

In the application of the present invention, the expression "audio-visual program" refers to any program that is possible in audio, video, or both audio and video. Such a program specifically consists of an MPEG-4 type multimedia program including, for example, several video and / or audio sequences, three-dimensional data, two-dimensional graphs and / or animation scripts associated therewith.

A method of distributing encrypted portions is known from patent document EP-1075108. In this method, one or more seed values can selectively communicate with a user terminal to locally play a limited set of decryption keys that enable decryption of a corresponding limited number of encrypted program portions. The communication of these seed values forms a breakdown of billing for the user, the amount of which may vary depending on the extent of decryption. Billing is calculated, for example, on a session or subscription basis. It is recognized that billing under a subscription billing system is difficult to be placed at the level of an audiovisual center that provides an encrypted program. In addition, session-based billing increases the overall cost to the user using an audiovisual service when the user benefits only a portion of the program.

Further, US Pat. No. 4,916,737 discloses a technique in which scrambled video and / or audio portions are broadcast and descrambled using a receiver decoder box. In addition, the telephone modem associated with this box is periodically connected with the operator's central computer to receive a temporary identification code valid for the next period. This code is sent by the central computer only after confirming the specific serial number for the relevant box. The periodicity of the transmission of the new code can be, for example, once a month, and this connection lasts only a few seconds so that the telephone line is not used for only very short periods and frequencies.

This technique is appropriate for the entire subscription over a given period of time and requires complex subscription management. This prevents billing in a simple way for programs that are actually watched by the user.

Patent US-4,890,322 describes a service for distributing a notification message used to control a TV signal per program. The transmitted encrypted signal is decrypted at each subscriber's stage by the decryption unit by using a non-dedicated telephone service line. In response to each order from the subscriber, the decryption unit automatically sends the subscriber's request to the distribution service via the telephone service line and in response receives coded key information necessary to decrypt the desired program over the same line. . The obtained key information is used during the period of the ordered program. By way of example, in the above description, key decryption is sent to the subscriber in the form of a repeated message for three seconds, the key being in the form of a number consisting of coded numerical values that can be used to fix the coefficients of the signal filter. .

This method makes it possible to bill per program but does not allow for more detailed billing (eg to watch a given broadcast portion), which requires the management of complex billing.

In order to improve the granularity of control in the user part, a demonstration is made of the independent transmission of program parts, each of which can form a history of a particular request. Thus, according to its usefulness, the user may watch the first portion of the movie at the first evening and then decide to watch the second portion at another evening. However, this solution is still more complicated in the management of transmission and billing, and if the offering is more sophisticated, for example, allowing the viewer to select the duration of the respective parts.

The present invention provides a method for distributing encrypted portions of an audio and / or video program that can provide security against intrusion and at the same time allow for simpler and more detailed billing of services.

The method according to the invention provides that, at the beginning of telephone communication from a user terminal to a call center, the transmission of the key as a sequence from the call center to the user terminal during telephone communication is synchronized with the distribution of successively encrypted portions of the program. It is done in such a way. Of course, the distribution of consecutive encrypted portions of the program may be performed by broadcast over the cable, and may also be performed by satellite or via broadcast propagation. The call center is preferably a center for receiving telephone calls of telephone operators, in which there is a means for measuring the time of telephone communication between them as each call of the user terminal, and therefore, based on this information, an appropriate bill is provided. It can be easily created for the corresponding user.

While telephony is established between the call center and the user terminal, decryption of the current portion of the program can be made locally at the user terminal. However, upon completion of telephony, the current encrypted portion of the program is no longer decrypted since the key no longer reaches the user terminal. Thus, the period of plain text receipt of the program corresponds to the entire period of the telephony, so that the user pays only for the actual period valid for him from the audiovisual service.

The method of the present invention is surprisingly contrary to the technique by which people seek to reduce as long as possible the duration of telephony required to obtain decryption data. In particular, the method of the present invention is opposed to the continuity of telephony in the distribution of encrypted programs. These features make it possible to charge this service directly by telephone billing, as well as to broadcast audiovisual programs in real time for a period of time accurately determined by the user.

The method according to the invention also advantageously exhibits the following features.

Telephony utilizes Internet protocols;

The synchronization time code is transmitted in communication with successive keys during telephone communication.

The invention extends to a decoder for a receiver of an audio and / or video program, wherein successive portions of the program are decrypted using different successive keys, which decoder is connected to a call center via a telephony interface, and the call It is characterized in that it is designed to be executed in a manner synchronous with the decryption of successive parts of the program by recovering consecutive keys as a sequence during communication with the center.

According to the good characteristics of this decoder:

The telephony interface is a specific telephone modem in the ADSL modem type utilizing the Internet protocol.

The invention also extends to a decoding routine suitable for loading into the memory of a decoder for a receiver of an audio and / or video program having a telephony interface.

The method for decoders and routines according to the present invention is described in more detail below, and is shown through a single diagram that schematically illustrates a system for cost distribution of video and / or audio programs.

The two user terminals T1, T2, shown by way of non-limiting example in FIG. 1, respectively, not only the telephone modem type communication interfaces M1, M2, but also the decoders D1, D2, and receivers R1, R2 of audio and / or video programs. Include.

Receivers R1 and R2 are herein television receivers. The communication interfaces M1, M2 respectively form an integral part of the decoders D1, D2, which may be decoders of the "set top box" type.

Each decoder D1, D2 may receive consecutive encrypted portions of an audio and / or video program on input channels C1, C2. These program parts are of digital construction.

The encrypted portions of the program are distributed to the user terminals T1, T2 by the RF channel 1 from the broadcast antenna 2 connected to the audiovisual center 3 providing the program herein. In the audiovisual center 3, consecutive portions of the program are encrypted using successive different encryption keys, limiting the possibility of infringement. The encryption key used to encrypt consecutive portions of the program is changed at the end of each sequence of n consecutive portions, and the value of n is different from the encryption key, for example every 30 seconds, in showing the program on the screen. It is adjusted to have.

The time code used in the digital audiovisual stream is known as the Decoding Time Stamp (DTS), the Presentation Time Stamp (PTS), and the Program Clock Reference (PCR) of the MPEG2-TS stream. These time codes are inserted into each encrypted part of the program, allowing the decoders D1 and D2 to be synchronized with the clock of the transmitter 3 of the audiovisual program.

According to one aspect of the invention, the time code of the DTS type is combined with various encryption keys while being encrypted at the audiovisual center 3. This combining, during the decryption of portions of the program at the decoder, decrypts the portion of the program if the time code associated with the decryption key provided for the portion of the program is not synchronized with the time code DTS recovered in this portion of the program. Provided to prevent.

Reference numeral 4 in FIG. 1 denotes a telephone call center that receives a continuous encryption key as a sequence from the audiovisual center 3, which reception is carried out in a manner synchronous with broadcasting successive parts of the program by the antenna 2. Then, the user terminals T1 and T2 receive these portions of the program as a sequence.

In order for the program to be shown in plain text at the levels of the receivers R1, R2 of the user terminals T1, T2, the user operates his decoders D1, D2, for example, via manual control F1, F2, or remote control, and this control Causes the decoder to initiate telephone communication with the call center 4 via the modem type communication interfaces M1 and M2. The call number of the call center is pre-recorded in the decoder to enable the initiation of automatic telephony. During telephone communication, decoders D1 and D2 can be identified by call center 4, after which the call center 4 provides for the decoding of the current parts of the program received in parallel by decoders D1 and D2. Current consecutive keys are transmitted to the user terminals T1, T2 as a sequence over the telephone path. The transmission of these keys, each combined with a time code, by the call center 4 as a sequence is performed in a manner synchronous with broadcasting parts of the program by the antenna 2. In Fig. 1, "X, Y, Z, ..." denotes successive decryption keys, and "t1, t2, t3, ..." denotes time codes associated with decryption keys.

At each decoder D1, D2, the decryption process checks that the successive keys combined with the time code recovered via the communication interfaces M1, M2 are compared with the DTS time code located in the encrypted portions of the program received by the decoder. It is organized in such a way. In other words, the key associated with time code t1 will be rejected if the program portion received in parallel with the recovery of this key contains a DTS time code prior to t1. Thus, this program part will not be decrypted at the decoder.

In practice, successive keys with each time code are recovered at the user terminal slightly ahead of the corresponding parts of the program, so these keys must be temporarily stored at the decoder to allow decryption during receipt of the current part of the program. When the key of time code t1 is recovered by the decoder, if the DTS time code of the current part of the program is earlier than time code t1 associated with the key, this key is stored in the decoder's temporary memory. In the opposite case, the key is rejected and thus not written to the decoder's temporary memory. During the decryption of the current part of the program, the key required for this decryption must be present in the decoder's temporary memory.

The decryption process described above may also be implemented as a routine that is loaded into the memory of a conventional programmable decoder equipped with a telephony interface.

The communication interface is preferably an ADSL type modem, which advantageously utilizes the Internet communication protocol to enable multiple communication on the same telephone line.

Claims (12)

A method of distributing encrypted portions of an audiovisual program to user terminals T1 and T2, wherein successive portions of the program are encrypted using different keys, The method further comprises, at the start of telephone communication from the user terminal to the call center 4, transmitting the key as a sequence from the call center to the user terminal during telephone communication, such that the distribution of consecutive encrypted portions of the program. Characterized in that it is made in a synchronous manner. The method of claim 1, wherein said telephony utilizes an Internet protocol. A method according to claim 1 or 2, wherein synchronization time codes are transmitted to the user terminal with the keys. The method according to any one of claims 1 to 3, Upon completion of the telephone communication with a user terminal, a period of telephone communication is determined at the call center, and a bill is generated in response to receipt of the program by the user terminal. The method according to any one of claims 1 to 4, The call center is a center for receiving telephone calls of a telephone operator. In decoders D1 and D2 for the receiver of an audiovisual program, successive portions of the program are decrypted using different successive keys, The decoder is connected to a call center 4 via telephony interfaces M1 and M2 to recover the successive keys as a sequence during communication with the call center and to synchronize the decryption of successive parts of the program. Characterized in that it is designed to run as, The decoder is preferably capable of decrypting distributed encrypted program parts according to the method according to any one of claims 1 to 5. 7. The decoder of claim 6 designed to recover synchronization time codes associated with the keys from the call center. 8. The decoder of claim 6 or 7, wherein the communication interface is a telephone modem. The decoder of claim 8, wherein the communication interface is an ADSL modem. 10. The decoder of any one of claims 6-9, wherein the communication interface utilizes an internet protocol.  In the method of decoding an audiovisual program as successive portions of the program are decrypted using different successive keys, the method is configured to be connected to the call center 4 using the telephony interfaces M1 and M2. And recover the continuous key as a sequence during communication with the call center and execute in a manner synchronous with decryption of the successive portions of the program, The method is preferably implemented by means of a decoder (D1, D2) according to any of the claims 6-10. In a decryption routine for decrypting successive portions of an audiovisual program using different successive keys, the decryption routine is designed to establish telephony communication with a call center 4 having a predetermined call number, during the telephony communication. Recover the successive keys from the call center and execute in a manner synchronized with decryption of successive portions of the program, The routine is preferably configured to implement the decoding method according to claim 11.