JP4987850B2 - Security method and device for managing access to multimedia content - Google Patents

Description

  The present invention relates to a method for transmitting digital or multimedia content to a mobile terminal, and more particularly to encrypted content in the form of an audiovisual program.

  Most current solutions for broadcasting encrypted audiovisual programs via cable or satellite have significant security weaknesses exploited by numerous fraudsters. Even today, fraudsters even organize networks for distributing code and software to create code that is essential for decryption of broadcast programs (some of which include movie films or football games). Some of them have high added value, such as live shows.)

  For one thing, there is no permanent and individual two-way connection with the user in the existing system, and thus verifying the user's right to view the encrypted program in real time. Is caused by being impossible. Many subscribers use basic viewing, but can successfully obtain a code corresponding to a higher level right and thus benefit from the right without paying for the right It is.

  Furthermore, there is currently no way to resume playback of encrypted content from where it was interrupted due to intentional or unintentional interruption by the user. For example, in the environment of a receiver in a mobile phone, browsing can often be interrupted by phone calls or interruptions in network coverage. This limitation is a great nuisance for users, especially in mobile environments.

  The present invention addresses the above drawbacks, and allows a mobile phone user to view an audiovisual program encrypted in a more secure manner, and to resume reception from where the interruption occurred. The aim is to propose possible solutions.

These objectives are that multimedia content is transmitted in encrypted form from a broadcast server and over a communications network,
a) transmitting multimedia content usage right data to the mobile terminal;
b) storing usage right data in the security module of the mobile terminal;
c) generating a series of encryption / decryption keys; d) transmitting the multimedia content to the mobile terminal;
e) the mobile terminal receives the multimedia content and decrypts the multimedia content using a decryption key from a series of decryption keys generated in the security module of the mobile terminal;
The decryption key series is generated from usage right data stored in the security module,
The content is achieved by a method for managing the transmission of multimedia content to a mobile terminal comprising a security module, characterized in that the content is encrypted with a continuous key from a series of generated encryption keys.

  In this way, multimedia contents such as audiovisual programs are transmitted to the mobile terminal in a secure manner by dynamically changing the encryption / decryption key in parallel between the broadcast server and the mobile terminal. Is possible.

  According to one aspect of the present invention, in order to allow playback to resume when a multimedia content transmission interruption occurs, the method can be performed by the mobile terminal using a cipher used from the last received frame or at the time of the interruption. A broadcast server reference data is transmitted from the activation key f) and a multimedia content broadcast step g) is resumed as an action of the reference data. In step c), each encryption / decryption key is generated at a time corresponding to a time interval defined by each frame transmitted by the broadcast server.

  As described above, according to the method of the present invention, it is possible for the user to return to the program at a position close to the interruption point regardless of whether the error is generated by the user or by an external factor.

  According to another configuration of the invention, the method further comprises the step h) of verifying the validity of the usage rights in the mobile terminal, wherein the verification is the usage rights data stored in the security module. And the use right data is compared with the use right data stored in the database.

  As a result of this verification, the service provider can verify the validity of the rights at any time (assuming the phone is within the network coverage area), modify the rights, and interrupt the service if necessary. Is possible.

  In order to enhance the security of multimedia content transmitted over the communication network, in step c), the key of the series of decryption keys is repeatedly calculated based on the basic key and the secret code, and the secret code is pre- And is exchanged between the mobile terminal and the broadcast server.

  For example, for a mobile phone with a (U) SIM card, the present invention uses a key that changes dynamically in time according to a series known only to the (U) SIM card and the service provider. A method of encrypting the program is proposed. These keys are repeatedly calculated based on the rights acquired by the user before the program is transmitted and stored in the (U) SIM card. The validity of these rights can be verified at any time as long as the user is inside the network coverage area. The service provider can reject (or not) the rights verified in this way at any time.

(U) Reinitialize the decryption means at a time close to a user intended or unintentional interruption by communicating the criteria supplied by the SIM card to the server. The method
(A) storing the user's rights in a (U) SIM card comprising a basic encryption key;
(B) generating a series of keys defined by the service provider and used to encrypt the program at the frequency;
(C) Communicates to the service provider the criteria (eg key number or key itself) provided by the (U) SIM card and indicating the location where descrambling was interrupted in order to resume transmission of the program The generation is based on a basic key and is performed in parallel in the card or terminal and in the server of the service provider that encrypts and transmits the program, To do.

  The present invention also comprises a security module configured to be included in a mobile communication terminal, wherein the terminal is used to receive multimedia content transmitted in an encrypted format, It comprises means for storing usage data for media data, and means for calculating a series of descrambling keys from the stored usage data and storing the series.

  This module may further comprise means for storing reference data from the last received frame or from the decryption key that was used when the transmission of multimedia content to the mobile terminal was interrupted.

  As explained above, the present invention comprises a mobile terminal comprising a security module and a computer program intended to be executed in such a mobile terminal, the program comprising an encryption / decryption key And a command for decrypting multimedia content received by the mobile terminal using a decryption key from the generated decryption key series, the encryption The release key series is generated from usage right data received by the mobile terminal.

  The present invention further comprises a transmission server including means for transmitting multimedia content in an encrypted format to a mobile terminal including a security module via a communication network, and the server includes an encryption calculated in the server. And a means for transmitting the multimedia content usage right data transmitted with the data for calculating the decryption key series similar to the activation key series to the portable terminal.

  The server inquires a database for storing the usage right data to be transmitted to the mobile terminal and the usage right data stored in the security module of the mobile terminal, and stores the usage right data in the database. And means for comparing with the usage right data.

  The broadcast server comprises instructions for generating a series of encryption / decryption keys and data for calculating a series of decryption keys similar to the series of encryption keys calculated by the server; A command for transmitting multimedia content usage right data to a mobile terminal; and a command for transmitting the multimedia content to the mobile terminal. The present invention can be implemented using a computer program characterized in that the content is encrypted with a key.

  Finally, the present invention is also a multimedia content transmission management system comprising a mobile terminal equipped with a security module and a broadcast server as defined above.

  The features and advantages of the present invention will become more clearly apparent from the following description, given by way of illustrative and non-limiting example and with reference to the accompanying drawings.

  The present invention can be applied to any type of mobile terminal that includes a mobile phone or a screen and a security module, can communicate over a standard mobile phone network, and can receive multimedia content such as a digital audiovisual stream. Also applies. These devices are increasingly equipped with small pocket computers that, as is known, have the basic resources found in a standard computer on a smaller scale. More specifically, these telephones include, in particular, processing means such as a processor for executing a program and storage means for storing data. As is well known, the processor is a SIM (subscriber specific module) additionally comprising a non-intrusive solid box that provides a security level equal to or higher than that of a normal terminal, or It may be part of a USIM (universal subscriber identification module, usually denoted as (U) SIM) microchip card. As will be described in detail below, this makes it possible for the solution according to the invention to allow the terminal to manage the interruption of service ergonomically and to the service provider (eg Orange®). Configures the means to use a security module and a permanent two-way connection to the operator's network that allows immediate access to secure procedures for initialization, modification, verification and deprivation That is why. However, some portable terminals do not have an independent physical medium, for example, do not have a microchip card. In that case, the security module is directly implemented in the processing and storage means of the mobile terminal, and a part of the memory of the previous mobile terminal is reserved for data to be transmitted to the security module as described below. Is done.

  The detailed description is limited to a mobile phone terminal having a (U) SIM card.

  FIG. 1 is a simplified diagram illustrating the relationship between the main components used in the program transmission system and method according to the present invention. As shown in FIG. 1, the system includes a server 1 and a telephone 2 having a screen 21 and a removable (U) SIM subscriber card 3. The system further comprises a mobile phone network 4 that allows communication between the server 1, the telephone 2 and the SIM card 3. The server 1 controls communication and content security management (by specific encryption).

  The telephone 2 and the (U) SIM subscriber card 3 communicate via a software interface in a manner known to those skilled in the art. For example, in a cellular phone, this interface is standardized by ETSI (European Telecommunication Standards Institute). As a result, the server 1 can access the memory of the (U) SIM subscriber card 3 in the read mode and the write mode via the mobile phone network 4 and the telephone 2 in which the card is inserted.

  FIG. 2 is a diagram illustrating communication among the server 1, the telephone 2, and the (U) SIM card 3. Through this communication via the mobile phone network 4, the user's mobile terminal and (U) SIM card can be identified and authenticated (steps S1 and S2), and the usage rights acquired by the user can be obtained from the (U) SIM card. And secure storage (step S3). These rights typically comprise an association with the program to which the rights are associated, a decryption key, a component that ensures authentication of the rights, and the like, and various organizations (particularly Open Digital Rights Language Initiative and It is standardized by Open Mobile Alliance). For example, a SIM toolkit application can securely distribute these rights to a location in the card's memory. By storing the rights, if the phone is used within the coverage area of the mobile network and in accordance with the standardized GSM / UMTS protocol, the service provider can then store it on the (U) SIM card at any time thereafter. A certain right can be verified, modified, and rejected if necessary.

  One example of this scenario is a modification of these rights that is accomplished immediately via the mobile network, either on the initiative of the subscriber or on the initiative of the service provider. If the service provider wishes to modify the rights, it is sufficient to store the new rights instead of the old rights.

  The steps executed when the transmission of the TV program according to the present invention is resumed will now be described with reference to FIGS.

  As shown in FIG. 3, after the (U) SIM card 3 obtains the usage right as described above, the server 1 transmits the audiovisual program in encrypted form to the telephone set 2 via the mobile communication network 4. Depending on the transmission technique used to transmit the data over the mobile phone network (e.g. UMTS (3G) network, for example), a time interval Δt defining a time interval Δt for transmitting a part of the audiovisual program data to the telephone set 2 is defined. The audiovisual program is broadcast in the frames T1 to Tn. As a result, each frame corresponds to a particular point in time (or time domain) of the audiovisual program being transmitted, depending on the frame position in the transmission system and the time interval represented by the frame. According to the first configuration of the present invention, the (U) SIM card can store the number of each received frame and can indicate the last frame number received at the time of interruption. According to another configuration of the present invention, each frame is encrypted with a frame-specific encryption key so that each frame T1 to Tn in FIG. 3 can be identified with a different encryption key. Is possible. The (U) SIM card 3 that has received the right to decrypt the program transmitted to the telephone generates a series of decryption keys similar to the series of encryption keys C1 to Cn. As a result, the (U) SIM card 3 is in a state indicating the encryption / decryption key used at any time during transmission.

  Therefore, when the program broadcast is interrupted, the mobile phone 2 requests to resume transmission of the previously interrupted program (step S4, FIG. 4). Next, the server 1 inquires of the (U) SIM card 3 when the transmission of the program is interrupted (step S5). The (U) SIM card then gives the server the basis of the last received frame or the key used to encrypt the last received frame, indicating when the interruption occurred. A response is made (step S6). If necessary, the server updates the rights stored on the (U) SIM card to resume transmission of the program from where it was interrupted (step S7).

  An embodiment for managing the criteria for keys used to encrypt broadcast content will now be described.

  There are various ways to generate these keys. One particularly secure solution is to use a common secret (such as a PIN) for the service provider and the user's card (depending on the solution employed, optionally a key diversification algorithm). To personalize this secret). This secret is entered into the card when the card is personalized or by secure download when applying for subscription to the service provider.

  Next, the first decryption key provided in the right associated with the digital content is used to encrypt / decrypt consecutive content frames on both the server side for encryption and the card side for decryption. A common secret is used to calculate the series of encryption / decryption keys to use.

  To calculate this series, for example, an encryption function such as another encryption algorithm such as the Advanced Encryption Standard (AES) algorithm, or an algorithm suitable for the length of this decryption key (usually 128 bits) May be used. This algorithm repeatedly applies to a used previous key and a secret to obtain the next key to use. This procedure is accomplished by decrypting in parallel using the “input” key of the encryption function.

  The secret is naturally updated using the GSM secure key download function as well as the service provider's initiative as a function on the requirements of the service provider.

  If the cipher is decrypted by the scientist community, the algorithm may be updated, which gives the service provider complete flexibility in terms of security architecture. Further, if necessary, a plurality of algorithms for changing from one to another may be provided in the card.

  Therefore, the same calculation is repeated both in the broadcast server and in the card, so that it has the same key series within both rights, so that the frame number or (other keys are It is possible to generate a series of criteria that may be either one of the key values used for the frame (encrypted using).

  As a result, in order to resume browsing following the interruption, the card dynamically stores this criterion, and if the server requests the criterion, it is sufficient to send the request. The browsing resumption method supported by this standard varies depending on whether it is a point-to-point transmission problem or a point-to-multipoint broadcasting problem. These methods are known to those skilled in the art and are not described in further detail herein for the sake of simplicity.

  FIG. 5 illustrates the steps performed to verify the usage rights.

The mobile phone 2 may be in the coverage area of the mobile phone network 4 and selectively reading (ie, descrambling) audiovisual content transmitted by the service provider. The server 1 transmits a command that the user holds and verifies the validity of the rights stored on the user's (U) SIM card 3 (step S10). (U) The SIM card 3 then responds to the server by indicating the rights held by the user. The response format from the (U) SIM card to the server depends on the protocol used. For example, the (U) SIM card may respond to the server by sending an encrypted SMS message corresponding to the user's rights to the server (3GPP standard 23.048). The usage rights granted to the user are very diverse. They typically address restrictions or limitations on the use of multimedia content. These restrictions or limitations are interpreted by the DRM agent (software that accomplishes certain digital rights management operations) and apply to the targeted multimedia content.
For example, the usage rights are:
• Content expiration date • Number of times the content can be used • Identification information that can be associated with the content • (eg, the user must be within the coverage area of the mobile network to make the content available) It is also possible to use special provisions.

  The usage right may be expressed in various languages determined by the adopted rights management technology. For example, the usage rights may be described in ODRL (Open Digital Rights Language) used in the OML (Open Mobile Alliance) standard, and XrML (extensible rights) used in the Windows Media (registered trademark) DRM platform. May be described.

  Since bidirectional communication exists in the mobile network, the (U) SIM card response regarding the usage rights held by the user is then transmitted to the service provider via the mobile network (step S11). In this way, it is possible to verify the validity of the usage right by comparing the usage right with the right acquired in advance by the user and stored in the user database. If there is a discrepancy, the server can direct a survey to account for the discrepancy (eg, database synchronization delay following a recent transaction). If the user detects the intended fraud, the provider will charge for access to programs that, for example, destroy all rights contained in the card or illegally added to the card By doing so, appropriate measures may be taken immediately. The method used to destroy the rights is similar to the method used to store or modify the rights in the card, as already described (see FIG. 1).

FIG. 1 is an overview of the system used in the present invention. FIG. 2 illustrates one embodiment of data management according to the present invention in a (U) SIM card. FIG. 3 illustrates one embodiment for transmitting an encrypted audiovisual program. FIG. 4 illustrates one embodiment of key recovery for resuming program reception according to the present invention. FIG. 5 is an example of rights validation that allows a service provider to reject (or not) a user's rights following rights validation.

Explanation of symbols

1 Broadcast Server 2 Mobile Terminal 3 Security Module 21 Screen

Claims (9)

From the broadcast server (1), the portable terminal equipped with a security module (3) (2), and via a communication network (4), the multimedia content is transmitted in encrypted form, the multimedia content transmission management method In
Said method comprises
a) transmitting multimedia content usage right data to the mobile terminal (2);
b) storing the usage right data in the security module (3) of the portable terminal (2);
c) generating a series of encryption / decryption keys;
d) transmitting multimedia content to the mobile terminal (2) ;
step e) said portable terminal, which receives the multimedia content, for decrypting the multimedia content using the decryption key from the series of decryption keys generated in said mobile terminal security module And
The decryption key series is generated from the usage right data stored in the security module (3),
The content is encrypted with a sequence of keys from a series of generated encryption keys;
The broadcast server (1) encrypts each frame of multimedia content with a different encryption key of the series of encryption keys such that each frame is identified by a different encryption key;
The security module (3) of the mobile terminal (2) generates a series of decryption keys similar to the series of encryption keys;
When the method interrupts transmission of multimedia content,
f) the portable terminal transmitting reference data from the encryption key used at the time of interruption to the broadcast server;
g) resuming broadcasting of the multimedia content as an action of the encryption key transmitted in step f) ;
The method of further comprising. In step c)
Method according to claim 1, characterized in that each encryption / decryption key is generated at a time corresponding to a time interval defined by each frame transmitted by the broadcast server (1).   Step h) further comprising the step of verifying the validity of the usage right in the portable terminal, the verification examining the usage right data stored in the security module and storing the usage right data in a database; 3. A method according to claim 1 or claim 2, wherein the method is achieved by comparing with stored usage rights data.   In step c), the keys of the descrambling key series are repeatedly calculated based on the basic key and the secret code, the secret code being defined in advance, the mobile terminal (2) and the broadcast server (1) The method according to claim 1, wherein the method is exchanged between and. A security module (3) adapted to be provided in a portable terminal (2),
The terminal is used to receive multimedia content transmitted in an encrypted form with a series of encryption keys ;
Means for storing usage rights data of multimedia content;
Means for calculating a series of decryption keys from the stored usage right data and storing the series;
Each frame of multimedia content is encrypted with a different encryption key of the series of encryption keys such that each frame is identified by a different encryption key;
The security module (3)
Means for generating a series of decryption keys similar to the series of encryption keys used to encrypt the multimedia content;
Means for transmitting reference data from an encryption key used when transmission of multimedia content to the portable terminal is interrupted ;
A security module comprising: In a portable terminal (2) having a display means,
A portable terminal comprising the security module according to claim 5. In a broadcast server comprising means for transmitting multimedia content in encrypted form to a mobile terminal (2) comprising a security module (3) via a communication network (4),
Means for transmitting right-of-use data of multimedia contents to the portable terminal , wherein the server comprises data for calculating a series of decryption keys similar to the series of encryption keys calculated by the server Comprising
The broadcast server comprises means for encrypting each frame of multimedia content with a different encryption key of the series of encryption keys such that each frame is identified by a different encryption key;
The broadcast server is adapted to perform an operation of examining the security module (3) of the portable terminal (2) with respect to the encryption key used at the time of the interruption when the multimedia content is interrupted. A broadcast server characterized by the above. A database that stores usage rights data sent to mobile devices,
8. The method according to claim 7 , further comprising means for inquiring about the usage right data stored in the security module of the portable terminal and comparing the usage right data with the usage right data stored in the database. The server described in. In the multimedia content transmission management system,
A portable terminal (2) according to claim 6,
A broadcasting server according to claim 7 or 8 ,
A system characterized in that the terminal comprises a security module (3) according to claim 5.

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