EP2220865A2

EP2220865A2 - Method and system for the secure distribution of audiovisual data by transactional marking

Info

Publication number: EP2220865A2
Application number: EP08871552A
Authority: EP
Inventors: Octavian Folea; Didier Lesteven
Original assignee: Nagra France SAS
Current assignee: Nagra France SAS
Priority date: 2007-10-30
Filing date: 2008-10-30
Publication date: 2010-08-25
Also published as: CN101897182B; FR2923126A1; WO2009092894A2; KR101535694B1; WO2009092894A3; CN101897182A; FR2923126B1; US8861729B2; US20100208891A1; KR20100092945A

Abstract

The invention relates to a method for distributing a marked audiovisual sequence (106) on the basis of a nominal audiovisual sequence (1) to a destination apparatus (11), said nominal audiovisual sequence having a nominal content, the method comprising steps in which: - a first mark is generated which is able to be applied to the initial content at marking positions (112); - a modified stream (101, 110) is generated, having a modified content different from said nominal content; - a complementary stream (103) is generated comprising complementary information calculated so that it is possible to reconstruct an audiovisual sequence altered for human perception on the basis of said modified stream as a function of said complementary information, - said modified stream and said complementary stream are transmitted to said destination apparatus; the method being characterized in that: - said complementary information is calculated as a function of said marking positions (112); - a second mark different from the first mark is generated on the destination apparatus and in that - said marked audiovisual sequence (106), which is not altered for human perception is reconstructed by the second mark at the level of said marking positions on the basis of said stream modified as a function of said complementary information.

Description

METHOD AND SYSTEM FOR SECURE DISTRIBUTION OF

AUDIOVISUAL DATA BY MARKING

transactional

The invention relates to a method for the distribution of audiovisual sequences.

In order to protect an audiovisual sequence against piracy, it is known to tattoo the audiovisual sequence, in a visible or invisible manner, so as to identify the holder of a pirate copy.

It is also known to encrypt the audiovisual sequence during a transmission in order to prevent the illegal reading of the sequence.

It is certainly possible to combine these two protection methods by encrypting the audiovisual sequence at an encryption module of the transmitting coast, and by tattooing the sequence after decryption at a tattoo module of the receiving coast.

However, such a method would not prevent a fraudster to recover the sequence output of the decryption module before passing through the tattoo module. Such a fraudster could then freely use the untattooed audiovisual sequence, if he could decrypt the sequence.

In order to solve this general problem, there is known a method for the distribution of a labeled audiovisual sequence from a nominal audiovisual sequence to a recipient equipment, said nominal audiovisual sequence having a nominal content, the method comprising steps in which:

a first mark is generated which can be applied to the initial content at marking positions; generating a modified stream having a modified content different from said nominal content;

a complementary stream is generated comprising computed complementary information so that it is possible to reconstruct an altered audiovisual sequence for human perception from said modified stream according to said complementary information,

- Transmitted to said destination equipment, said modified stream and said complementary stream.

Such a method is known from the application WO 2004/062281. In one embodiment of this application, the complementary stream includes marking instructions for inserting an invisible and personalized mark into the marked audiovisual sequence. In a preferred embodiment of the application WO 2004/062281, these instructions make it possible in particular to invert the LSB of certain visual coefficients, such as the DC coefficients. The absence or absence of an inversion on an LSB will, during an identification step, determine the first mark inserted in the audiovisual sequence. These instructions being inserted into the complementary stream, a fraudster could not have access to audiovisual content before applying the marking instructions, and therefore the insertion of the first personalized mark.

However, such a method does not provide effective protection when broadcast to destination equipment in "broadcast" mode. Indeed, in broadcast mode, the data transmitted to the different recipients are identical for all recipients. Therefore, if one applied the method described in the embodiment of the application WO 2004/062281 previously described, the marking instructions contained in the complementary flow would be identical for all recipients and it would therefore not be possible to distinguish pirate copies.

In the light of the aforementioned document, a problem to be solved by the invention is to allow a personalized marking of the audiovisual sequence broadcast in broadcast mode.

The present patent application proposes to solve this problem by means of a method as previously described in which:

said complementary information is calculated as a function of said marking positions;

- the receiving equipment is generated with a second brand different from the first brand and

said marked audiovisual sequence, which is not altered for human perception, is reconstituted by the second mark at said marking positions from said modified flux as a function of said complementary information.

The invention thus relates to a method for distributing a labeled audiovisual sequence from a nominal audiovisual sequence to a destination equipment, said nominal audiovisual sequence having a nominal content, the method comprising steps in which:

a first mark is generated which can be applied to the initial content at marking positions;

generating a modified stream having a modified content different from said nominal content; a complementary stream is generated comprising computed complementary information so that it is possible to reconstruct an altered audiovisual sequence for human perception from said modified stream as a function of said complementary information, said transmitting, to said destination equipment, said modified stream and said complementary stream; in which

said complementary information is calculated according to said marking positions;

In order to be able to securely distribute audiovisual sequences marked with a personalized mark to a plurality of recipient equipments using one of the broadcast distribution means, the skilled person knows techniques which incite him to consider two main solutions.

The first solution would be to generate a plurality of audio-visual sequences marked with a personalized mark for each recipient equipment and send this plurality of marked audiovisual sequences to all the destination equipment, each equipment receiving in this case all the marked audiovisual sequences. This solution can not be put into practice for a distribution such as digital television, which is supposed to work for thousands or millions of users, the broadcast transmission network can not carry such a huge amount of data u fact of his physical limitations. In addition, such a system would present a significant security disadvantage, because a malicious user, having access to all marked sequences, could borrow a false identity or it could erase the mark. The second solution would be to generate an audiovisual sequence protected by cryptographic means and send it to a plurality of recipient devices, each device being provided with means that allow it to generate a personalized mark and insert it into the audiovisual sequence. deprotected before or at the time of consumption of said audiovisual sequence. The disadvantage of this solution is that a malicious user could access the original audiovisual sequence by bypassing the system by recovering the deprotected and unlabeled audiovisual sequence after the de-protection phase of said audiovisual sequence and before the insertion phase of the mark in the audiovisual sequence.

The present invention proposes to overcome this drawback by sending to a plurality of recipient devices a unique piece of information for all the recipient equipment: the modified stream and the complementary stream. These two streams are determined on the server in order to allow the reconstitution of an altered audio-visual sequence with respect to the original audiovisual sequence, and different from that one at marking positions determined according to a first tattooing step of the audiovisual sequence of origin with a first mark.

The same two streams are accessible on the destination devices, once distributed by broadcast means by a server. The modified stream alone does not allow the user of the recipient device access to the original audiovisual sequence, because the modified stream is illegible and / or inaudible from the point of view of human perception. The access to the complementary stream also does not allow the user access to the original audiovisual sequence, because the audiovisual sequence obtained from the modified stream according to the complementary stream has always an altered representation for human perception, even if it is closer to the audiovisual representation of the original audiovisual sequence than is that of the modified flow alone.

In order to be able to consume the audiovisual sequence, the user must generate a second mark which will be used to determine an audiovisual sequence marked by said second mark at said marking positions from said modified stream as a function of said complementary information contained in the complementary stream. . This marked audiovisual sequence can be personalized for each recipient equipment, which makes it possible to identify the authors of any illicit use of a marked audiovisual sequence. Similarly, a malicious user attempting to recover the original audiovisual sequence would be unable to do so, as he does not at any time have the unprotected and unprotected audiovisual sequence, even if he circuit the normal operation of the system on its recipient equipment.

According to one embodiment, the step of distributing said marked audiovisual sequence comprises a step in which the marking positions are transmitted to said destination equipment.

This simplifies the operation of detecting said marking positions on client equipment limited in terms of hardware or software resources.

Thus, according to the invention, said complementary flow is determined as a function of said nominal flow and said marking positions. According to one embodiment of the invention, the step in which a first mark is generated which can be applied to the initial content at marking positions comprises steps in which: a content marked by said first mark is generated;

comparing from the point of view of the bit, said marked content and said nominal content so as to determine said marking positions.

This embodiment has the advantage of allowing the use of any tattooing device to mark the nominal content with the first mark.

According to another embodiment of the invention, said marking positions are determined by a tattooing device from said nominal content.

This makes it possible in particular to simplify the step of determining said marking positions by refraining from comparing the binary level between said marked content and said nominal content.

According to one embodiment of the invention, the step in which the complementary stream comprising said complementary information is generated comprises steps in which:

a complete complementary stream is generated comprising complete complementary digital information capable of allowing the reconstruction of the nominal content from the modified content; said complementary digital information is determined according to the complete complementary information and said marking positions. According to one embodiment of the invention, the step in which the complementary stream comprising said complementary digital information is generated comprises:

a step of extracting from said nominal content the information that can be marked with said first mark at said marking positions;

a step of determining a protected digital information by scrambling said information that can be marked;

a step of generating a protected content from said nominal content by replacing said information that may be marked by said protected digital information, said additional information being determined from said protected content so as to be able to reconstitute said protected content.

Thus, according to the invention, once the two streams (the modified stream and the complementary stream) have been generated, the said flows are transmitted to the destination equipment. This transmission step is performed by means of a network connection.

According to one embodiment, said marking positions are also transmitted to the destination equipment.

In order to be able to transmit said streams to destination equipments that do not have a network connection, the step of transmitting said streams is carried out by means of a physical medium.

In order to improve the protection of the audiovisual sequence against possible fraudsters, the complementary stream may include information relating to the digital rights associated with the nominal audiovisual sequence.

In order to simplify the communication infrastructure used for the distribution of two or three streams to the recipient user, said streams can be transmitted in the same communication channel or on the same physical medium.

In order for potential fraudsters to be unable to detect the marking and for an authorized user not to be hampered in the consumption of the marked audiovisual sequence, said marked content is visually and audibly identical to the nominal content.

So that a user can have access to certain information of the nominal audiovisual sequence without being able to consume this sequence satisfactorily without particular authorization, said nominal audiovisual sequence has a nominal format and in which said modified content has a format identical to said nominal format .

According to one embodiment of the invention, the step in which said marked audiovisual sequence is reconstructed comprises a step in which

a modified and marked stream is determined from said modified stream as a function of said second mark, said marked audiovisual sequence being determined from said modified stream and marked according to said complementary stream.

a modified and marked information is determined from said modified flux as a function of said marking positions and said second mark, said marked audiovisual sequence being determined from said modified and marked information as a function of said complementary stream.

According to one embodiment of the invention, the step in which said marked audiovisual sequence is reconstructed comprises steps in which:

generating marked information containing data marked from said modified stream according to said second mark;

additional information marked from said complementary stream is determined according to said marked information, said marked audiovisual sequence being determined from said modified stream as a function of said marked additional information.

generating information marked from said modified stream according to said marking positions and according to said second mark; additional information marked from said complementary stream is determined according to said marked information and said marking positions, said marked audiovisual sequence being determined from said modified stream as a function of said marked additional information.

In order to obtain a marked audiovisual sequence which is also personalized, said second mark may understand a personalization identifier. This personalization identifier may comprise a unique identifier of said destination equipment and / or a unique identifier of a user of said destination equipment, and / or a unique identifier of said marking operation, and / or the date of the attempted consumption, and / or the hourly information of said consumption attempt.

This then allows customization of the marked content according to the chosen identifier, possibly using a database of identifiers. The marking according to the invention may therefore include a tattoo and a personalization.

According to one embodiment of the invention, the step in which said marked audiovisual sequence is reconstructed comprises a step that comprises

a step of extracting protected information located at the marking positions in said modified stream, said marking positions being determined by analyzing said modified stream;

a step of determining the information that can be marked by descrambling from said protected information;

a step of altering said modified stream by replacing in said modified stream said information protected by said information that can be marked.

According to another embodiment of the invention, the step in which said marked audiovisual sequence is reconstructed comprises a step that comprises

a step of extracting the protected information located at the marking positions in said modified stream; a step of determining the information that can be marked by descrambling from said protected information;

a step of altering said modified stream by replacing in said modified stream the information protected by said information that can be marked at said marking positions.

The invention also relates to a system for the distribution of a marked audiovisual sequence from a nominal audiovisual sequence to a destination equipment, said nominal audiovisual sequence having a nominal content, the system comprising:

means capable of determining marking positions where a first mark is likely to be applied to said nominal content;

means capable of generating a modified stream having a modified content different from said nominal content;

means capable of generating a complementary stream comprising computed complementary information so that it is possible to reconstruct an altered audiovisual sequence for human perception from said modified stream according to said complementary information; means capable of transmitting, to said destination equipment, said modified stream and said complementary stream; in which

said complementary information is calculated according to said marking positions; said altered audiovisual sequence is different from said nominal audiovisual sequence at said marking positions; and wherein the system comprises: means capable of generating a second mark different from said first mark;

means capable of enabling the reconstruction, at the level of the destination equipment, of said marked audiovisual sequence, which is not altered for human perception, by the second mark at the marking positions from the modified stream; depending on the additional information.

According to one embodiment, the means capable of generating said second mark are arranged so as to carry out an operation of marking said complementary stream according to said second mark.

According to one embodiment, the means capable of generating a second mark are arranged so as to carry out a marking operation of said modified stream according to said second mark.

According to another embodiment, the system comprises means capable of altering the modified stream to allow the reconstruction of said marked audiovisual sequence.

Several embodiments of the invention will now be described with reference to the appended figures in which:

FIG. 1 illustrates the overall architecture of a system for implementing a method according to a first embodiment of the invention;

FIG. 2 illustrates the overall architecture of a system for implementing a method according to a second embodiment of the invention;

FIG. 3 illustrates the overall architecture of a system for the implementation of a method according to a third embodiment of the invention.

FIG. 4 details a component of the system for the implementation of a method according to the second and third embodiments of the invention.

- FlG. 5 details another component of the system for the implementation of a method according to the second and the third embodiment of the invention.

In the figures, identical references refer to similar technical elements, unless otherwise indicated below.

An embodiment of the invention will now be described with reference to FIG. 1 which illustrates the overall architecture of a system for implementing the method according to the invention.

In FIG. 1, in server equipment 14, audiovisual content 1 undergoes two main operations. The initial digital audio-visual stream 1 is sent to an analysis device 2 which uses the characteristics of the audiovisual coding format of the initial audiovisual stream 1 to determine a modified main stream 101 and a complete complementary digital information item 102. The modified main stream 101 a the same format as the initial stream 1 but has undergone modifications of certain parameters, being thus readable on a standard player of this format, but the display of the corresponding audiovisual content is not correct from the point of view of human perception. In the case of the MPEG digital audio-visual standard, the modifications made to the initial stream 1 may be: substitution of certain DCT coefficients of certain blocks, substitution of information on the motion compensation, substitution of the scanning order of the coefficients of certain images, substitution of quantization parameters etc. The complete supplementary information 102 extracted represents in this case only about 1% of the data of the modified main stream

101 to almost completely obscure visually and / or audibly the original digital audiovisual stream 1. The modifications made and any original information replaced in the modified main stream 101 are stored in the complete complementary digital information.

102 so as to allow a reconstruction of the digital audiovisual stream 1 from the modified main stream 101 as a function of the complete complementary digital information 102.

The complete complementary information 102 may therefore comprise data (for example coefficients describing the original digital stream or extracts of the original stream) and functions (for example, the substitution or permutation function). A function is defined as containing at least one instruction relating data and operators. The complementary digital information 102 describes the operations to be performed to recover the original stream from the modified stream.

The complete complementary information 102 and the modified main stream 101 can be generated as in the application WO 2004/015996.

In the context of the second analysis step, the initial audio-visual stream 1 is sent to a tattooing device 3 to determine a marked audio-visual stream 1 1 1 with a first mark. This first brand is generically generated so that its audiovisual representation is identifiable, and preferably annoying for the user who would like to consume the audio-visual stream marked 1 1 1. The generation of such a first generic mark and such a marked audiovisual stream can be made as in the application WO9965241. In the document WO9965241, the insertion of this generic mark is done by identifying all the MPEG segments in each frame video where the data can be modified to insert said generic mark. This generic mark is called "running mark" in particular on page 1, 2 and 7 of document WO9965241.

The extraction device 5 determines marking positions 1 12 by comparing, at the binary level, the tattooed audiovisual stream 1 1 1 and the initial audiovisual stream 1. The marking positions 1 12 represent the part of the tattooed audiovisual stream 1 1 1 which is different from the initial audiovisual stream 1.

According to an alternative embodiment, the marking positions 112 can be constructed directly by the tattooing device 3.

Complementary information 103 is determined by a composition device 6 as a function of the data located at the marking positions 1 12 in the marked flow 1 1 1 and complete complementary information 102. The composition device 6 copies first the complementary complete information 102 in the complementary information 103 and then it inserts the tattooed data of the marked flow 11 1 located at the marking positions 112 in the complementary information 103. In the case where the marking positions 1 12 and the complete complementary information 102 contains references to the same part of the initial audiovisual content 1, the data relating to these references in the complementary information 103 will be replaced by those of the marked flow 11 1 located at the marking positions 1 12.

Complementary information 103 may comprise data (for example coefficients describing the original digital stream or extracts from the original stream) and functions (for example, the substitution or permutation function). A function is defined as containing at least one instruction relating data and operators. Complementary information 103 describes the operations to be performed to recover part of the original stream.

Complementary information 103 may comprise the set consisting of complete complementary information 102 and tattooed data at marking positions 1, 12. The numerical format of the two types of information (complementary and complementary complete) is identical; which makes it impossible to separate the complete complementary information 102 from tattooed data at the marking positions 1 12, once the complementary information 103 is generated. This feature brings an important advantage: the separation of the two processes (that of reconstitution of the original flow and that of tattooing) becomes impossible, even for a compromised client station following a successful hacking attempt.

The sending of at least one of the two pieces of information (the complementary information item 1 03 and the marking positions 1 12) to the audiovisual decoder 1 1 is secured by one of the protection systems 7 well known to those skilled in the art. .

Complementary information 103 is transmitted via the broadcast and transmission network 10 at or before the display of said digital audiovisual program 1. It can also be packaged with most of the modified main stream 101 by the packaging device 8 by being for example added to the additional data or metadata of the file comprising the modified main stream 101. According to one embodiment, the complementary information

103 and the marking positions 1 12 are transmitted together or separated via the broadcast and transmission network 10 at or before the display of said digital audiovisual program 1. They can also be packaged with most of the modified main stream 101 by the packaging device 8 by being for example added to the complementary data or to the metadata of the file containing the stream. modified principal 101.

A user having home equipment recipient 1 1 can read any audiovisual content from the telecommunications network 10 or from the physical media reader 91. When it wishes to view the modified audiovisual stream 101, it can only do so by retrieving the complementary digital information 102 and possibly marking positions 1 12.

A demultiplexer 81 transmits on the one hand, the modified main stream 101 to a buffer memory 104 and, on the other hand, the protected supplementary information 103 and possibly the protected marking positions 1 12 to a deprotection module 71 compatible with the protection system 7.

The deprotection module 71 transmits the complementary information 103 in the clear to a buffer memory 107 and possibly the marking positions 1 to 12 in clear to a buffer memory 108 in accordance with the restrictions imposed by the protection system 7.

A tattooing device 31 generates a second mark and calculates on the fly a marked information containing marked data at marking positions 1 12 from the buffer 104 containing the portions of the modified audiovisual stream 101, said marked information and said marking positions 1 12 being sent to a buffer memory 1 16. The said marked data can be customized by generating a second different mark for each reading / consumption. Once the marked information inserted in said original stream, the identification of the reading / consumption is possible even if the recompiled stream is subject to hacking attempts of the type re-encoding or analog or digital capture. The generation of such a second mark and such marked data can be made as in WO9965241. The second mark is called "source-of-copy message" especially on page 4 of WO9965241 and the marked data are called "message holes" and are generated according to the "source-of-copy message" as indicated on page 1 1 of the document WO9965241.

In an alternative embodiment, the tattooing device 31 calculates on the fly a marked information containing data marked from the two buffers 104 and

108 which contain the synchronized parts of the modified audiovisual stream 101, respectively the marking positions 1 12.

The tattooing device 31 employs tattooing techniques equivalent to those employed by the tattooing device 3.

A complementary and marked information is composed on the fly by a composition device 6 from the two buffer memories 1 and 16 which contain the synchronized parts of the marked information and its references, respectively complementary information 103, said information complementary and marked being sent to a buffer 105.

The format of the information contained in the buffer memory 105 is the same as that of the information contained in the buffer memory 107.

A synthesis device 21 retrieves, on the fly, the tattooed audiovisual stream 106 with the second mark from the two buffers 104 and 105 which contain the synchronized portions of the modified audiovisual stream 101, respectively of the complementary and marked information produced by the device. 6. The tattooed audiovisual stream 106 is identical to the initial stream 1 from the point of view rendered audiovisual, but it contains an invisible mark detectable by means well known to those skilled in the art. The tattooed audiovisual stream 106 is decoded by the audiovisual decoder 23 and is returned to the consumer using the rendering device 12.

Advantageously, the tattooed stream is sent to a recording module 13 for making a private copy of the content on a physical medium such as a DVD, a CD or a memory card.

The general principle of a method for securing an audiovisual stream is explained below. The objective is to authorize on-demand audiovisual, on-demand and digital television services across all broadcast networks and local recording in the user's digital set-top box memory, the set-top box 1 1 can be a decoder connected to a television, a personal computer type PC or MAC, a handheld device such as a phone or a personal assistant type PDA 12. The solution is to tattoo, by one or more tattoo algorithms, the complementary information 103, which is represented by a small part of the audiovisual program 1, this part being essential for listening to and / or partially visualizing said audiovisual program 1 on a screen, but being of a very small volume compared to the total volume Digital audiovisual program 1.

Said complementary and marked information of the audiovisual program 1 is composed by the complementary information 103 which allows the partial reconstitution of the original stream 1 from the modified stream 101 and the tattooed data containing a second mark in the buffer memory 1 16, which allows mark the content in an invisible or inaudible way. Thus, the fraudulent digital or analog copy of such tattooed content 106 allows the traceability of the malicious user by analyzing said second mark. The main stream modi fi ed 1 01 is distributed freely to users and between users in a physical manner on any type of media such as memory cards, CDs, DVDs, peripheral devices external storage 9 etc. The modified main stream 101 can be read by a conventional reading device of this type of media like CD-ROM drive and / or DVD, memory card reader 91 etc. Alternatively, the modified main stream 101 is transmitted via a conventional telecommunication or broadcast network 10.

Complementary information 103 and possibly tattoo positions 112 are sent on demand via a narrowband telecommunication network 10 such as conventional telephone networks or cellular networks of GSM, GPRS or UMTS type or by using a small portion of a network of DSL or BLR type, or by using a subset of the shared bandwidth on a wired or satellite network.

Thus, the user never has on his equipment the entire original audio-visual stream 1 unprotected digital form, and can not reproduce it illegally. At worst, the user may have audiovisual content unprotected, but tattooed, which allows traceability copies fraudulently distributed and used. Advantageously, the complementary information item 103 and possibly the tattoo positions 1 12 are distributed using the same conventional telecommunication or broadcasting network 10 or the same physical medium 9 as the modified main stream 101. Advantageously, the complementary information item 103 and optionally the tattoo positions 1 12 are packaged in the modified main stream 101.

According to a particular embodiment, the consumption of audiovisual content is conditioned by digital rights. Digitale rights represent information that specifies the conditions under which content may be consumed: (a) the number of consumptions of the content, (b) the validity date to from which the content may be consumed, (c) the expiration date from which the content can no longer be consumed, (d) other types of rights, such as the domain for which consumption is permitted, the type of decoder 23 which allows consumption, etc.

Advantageously, digital rights on the consumption of the main digital stream are recorded by the protection system 7 in the complementary information 103 or with the protected tattoo positions 1 12 transmitted to the multiplexer 8. The complementary information 103, the tattoo positions

1 12 and the modified main stream 101 may therefore arrive indifferently in the recipient equipment 1 1, together or separately, by the telecommunication network 10 or via a physical medium 9 read by the reader 91 of its recipient equipment 1 1.

In a second embodiment with reference to FIG. 2 appended, a modified audiovisual stream 1 1 0 is built according tattoo positions 1 12. In this second embodiment, the analysis device 22 extends the functionality of the analysis device 2 by proposing additional steps applied before performing the functions of the analysis device 2, which consists in extracting, scrambling and replacing the information marked in the modified stream 1 10.

This makes it possible to apply the tattooing operation of the audiovisual stream to the client equipment before the audiovisual stream reconstitution operation is applied, and not at the same time, as in the first embodiment. This brings the advantage of increasing the safety of such a process.

The modified flow 1 1 0 is generated from the nominal flow 1 as a function of the tattoo positions 1 12 by the analysis device 22 by applying the following steps (with reference to FIG 4 appended):

a step 221 consisting in extracting from the nominal content 1 the information 1 13 intended to be marked with a first mark which is referenced in said nominal content 1 by the marking positions 1 12;

a step 222 consisting in determining a digital protected information item 1 14 by making the information to be marked 1 13 secure by at least one scrambling operation among those known to those skilled in the art;

a step 223 consisting in generating a protected content 1 15 by replacing in the nominal content the information intended to be marked 1 13 by the digital protected information item 1 14; a step of using the analysis device 2 to determine the modified stream 120 and the complementary information 3 from the protected content 1 15.

According to one embodiment, the parameters used to initiate the scrambling operations according to step 222 (cryptographic keys, type of algorithms, etc.) can be sent to the destination equipment together with the marking positions.

The modified stream 1 10 is employed in this second embodiment as the modified stream 101 in the first embodiment.

On the destination equipment, the contents of the buffer memory 104 are modified by the analysis device 32 before it is used by the tattoo device 31. To do this, the analysis device 32 applies the following steps (with reference to the appended FIG. a step 321 of analyzing the data contained in the buffer memory 104 in order to determine the positions where the data 114 are located and to extract from the buffer memory 104 said data 114; a step 322 consisting of determining the initial information 1 13 by applying at least one descrambling operation to the data 1 14, said descrambling operations having to comply with those applied according to the step 222, the parameters used to initiate said descrambling operations (cryptographic keys, type of algorithms, etc.) being retrieved in a secure manner from a hardware or software model on the destination equipment;

a step 323 of modifying the contents of the buffer memory 104 by replacing with the initial information 13 the existing information in the buffer memory 104 at the positions determined according to the step 321.

According to another embodiment, the analysis device 32 applies the following steps:

a step 321 of extracting from the buffer memory 104 the data 1 14 located at the positions referenced by the tattoo positions 1 12 contained in the buffer memory 108. - a step 322 consisting in determining the initial information 1 13 by applying to the data 1 14 at least one descrambling operation, said descrambling operations to be in accordance with those applied according to step 222 and the parameters used to initiate said descrambling operations (cryptographic keys, type of algorithms, etc.) being recovered from a secure way from a hardware or software module on the recipient equipment; a step 323 of modifying the contents of the buffer memory 104 by replacing the existing information in the buffer memory 104 by the initial information 13 at the positions referenced by the tattoo positions 1 12 contained in the buffer memory 108.

According to one embodiment, the parameters used to initiate the descrambling operations according to step 322 are recovered from the buffer memory 108.

Once the operations of the analysis device 32 have been applied, the behavior of the system is as described in the first embodiment.

In a third embodiment with reference to FIG.

3 appended, the tattoo device 33 generates on the fly information marked and modified from the buffer memory 104 containing the portions of the modified audiovisual stream 1 1 0, said marked and modified information being sent to a buffer memory 109.

According to another embodiment, the tattooing device 33 generates information on the fly marked and modified from the two buffers 104 and 108 which contain the synchronized parts of the modified audiovisual stream 1 10, respectively the marking positions 1 12, said marked and modified information being sent to a buffer memory 109.

The format of the information contained in the buffer memory 109 is the same as that of the information contained in the buffer memory 104. This allows the synthesis device 21 to use the contents of the buffer memory 109 in the same way as that of the buffer memory 104 as detailed in the previous embodiments.

Claims

1. A method for distributing a tagged audiovisual sequence (106) from a nominal audiovisual sequence (1) to a destination equipment (1 1), said nominal audiovisual sequence having a nominal content, the method comprising steps in which:

a first mark is generated that can be applied to the initial content at marking positions (1 12);

generating a modified stream (101, 1 10) having a modified content different from said nominal content;

a complementary stream (103) is generated comprising computed complementary information so that it is possible to reconstruct an altered audiovisual sequence for human perception from said modified stream according to said complementary information,

transmitting, to said destination equipment, said modified stream and said complementary stream; the method being characterized in that:

said complementary information is calculated according to said marking positions (1 12);

a second mark different from the first mark is generated on the recipient equipment, and in that the said marked audiovisual sequence (106), which is not altered for human perception, is reconstituted by the second mark at the level of the said marks; marking positions from said modified stream according to said complementary information.

2. Method according to claim 1 wherein the step in which a first mark is generated which can be applied to the initial content at marking positions (1 12). includes steps in which:

- generating a marked content (1 1 1) by said first mark;

- Comparing from the point of view of the binary said marked content (1 1 1) and said nominal content so as to determine said marking positions.

3. Method according to claim 1 wherein said marking positions according to the generation of said first mark are determined by a tattooing device (3) from said nominal content.

4. Method according to one of the preceding claims wherein the step of generating the complementary stream comprising said complementary information comprises steps in which:

a complete complementary stream (102) is generated comprising complete complementary digital information capable of allowing the nominal content to be reconstructed from the modified content; said complementary digital information is determined according to the complete complementary information and said marking positions.

5. Method according to one of claims 1 to 3 wherein the step of determining said additional information comprises:

a step (221) of extracting from said nominal content the information that can be marked (1 1 3) with said first mark at said marking positions; a step (222) of determining a protected digital information (1 14) by scrambling said tagable information (1 13);

a step (223) of generating a protected content (1 15) from said nominal content by replacing said information that can be marked (1 13) by said digital protected information (1 14), said complementary information being determined by from said protected content so as to reconstruct said protected content.

6. Method according to one of the preceding claims wherein the step of reconstituting said labeled audiovisual sequence (106) comprises a step in which said marking positions are transmitted to said destination equipment.

7. Method according to one of the preceding claims wherein the step in which is reconstructed said marked audiovisual sequence comprises a step in which

a modified and marked information item (109) is determined from said modified stream as a function of said second mark, said marked audiovisual sequence being determined from said modified and marked information (109) as a function of said complementary stream.

8. Method according to one of claims 1 to 6 wherein the step in which is reconstructed said marked audiovisual sequence comprises a step in which

a modified and marked information (109) is determined from said modified flux as a function of said marking positions and said second mark, said marked audiovisual sequence being determined from said modified and marked information as a function of said complementary stream.

9. Method according to one of claims 1 to 4 wherein the step of reconstituting said labeled audiovisual sequence comprises steps in which:

generating labeled information (1 16) from said modified stream according to said second mark; - additional information marked is determined

(105) from said complementary stream according to said tagged information, said tagged audiovisual sequence being determined from said modified stream based on said tagged additional information.

10. Method according to one of claims 1 to 6 wherein the step of reconstituting said labeled audiovisual sequence comprises steps in which:

generating labeled information (1 16) from said modified stream according to said marking positions and according to said second mark;

- Marked additional information (105) is determined from said complementary stream according to said marked information and said marking positions, said marked audiovisual sequence being determined from said modified stream according to said marked additional information.

The method of claim 5 wherein the step of reconstituting said tagged audiovisual sequence comprises a step (32) which comprises a step (321) of extracting protected information (1 14) located at the marking positions in said modified stream, said marking positions being determined by analyzing said modified stream; a step (322) of determining the information that can be marked (1 13) by descrambling from said protected information;

a step (323) of altering said modified stream by replacing in said modified stream said information protected by said information that can be marked.

The method of claim 5 wherein the step of determining said tagged audiovisual sequence comprises a step (32) which comprises

a step (321) of extracting the protected information (1 14) located at the marking positions (108) in said modified stream (104); a step (322) of determining the information that can be marked (1 13) by descrambling from said protected information;

a step (323) of altering said modified stream by replacing in said modified stream the information protected by said information that can be marked at said marking positions.

13. Method according to one of the preceding claims, wherein said second mark inserted in said marked audiovisual sequence comprises a personalization identifier.

14. The method of claim 13 wherein said personalization identifier comprises at least one of the following information: a unique identifier of said equipment recipient (11), a unique identifier of a user of said destination equipment, a unique identifier of the marking operation (31, 33).

15. The method according to one of the preceding claims, wherein in said marked audiovisual sequence is visually and audibly identical to the nominal content.

The method of any preceding claim wherein said complementary stream includes digital rights information associated with said nominal audiovisual sequence.

17. Method according to one of the preceding claims wherein said modified content has a format identical to said nominal format.

A system for distributing a tagged audiovisual sequence (106) from a nominal audiovisual sequence (1) to a recipient equipment (1 1), said nominal audiovisual sequence having a nominal content, the system comprising:

means (3, 5) capable of determining marking positions (1 12) in which a first mark is capable of being applied to said nominal content;

means (2, 22) capable of generating a modified stream (101, 1 10) having a modified content different from said nominal content;

means (6, 22) capable of generating a complementary stream (103) comprising computed complementary information so that it is possible to reconstruct an altered audiovisual sequence for human perception from said modified stream according to said complementary information; means (9, 10) able to transmit, to said destination equipment, said modified stream and said complementary stream;

The system being characterized in that: said complementary information is calculated according to said marking positions;

said altered audiovisual sequence is different from said nominal audiovisual sequence at said marking positions and in that it comprises

means (31, 33) capable of generating a second mark different from said first mark;

means (21, 6) capable of enabling the reconstruction at the destination equipment of said marked audiovisual sequence which is not altered for human perception by the second mark at the marking positions starting from the flow modified according to the additional information.

19. The system of claim 18 wherein the means (31) adapted to generate said second mark are arranged to perform a marking operation of said complementary stream according to said second mark.

20. The system of claim 18 wherein the means (33) capable of generating a second mark are arranged to perform a marking operation of said modified stream according to said second mark.

21. System according to one of claims 18 to 20 comprising means (32) adapted to alter the modified stream to allow the reconstruction of said labeled audiovisual sequence.