Method for local conditional access for mobile equipments

Inactive Publication Date: 2008-01-24
NAGRA FRANCE
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0016] The aim of the present invention is to provide countermeasure means in the event of piracy independently of the type of mobile equipment and at a relatively low cost. These means act on the protection elements that are not related to the standardization and that are preferably adjustable by the conditional access provider.
[0026] According to a first embodiment, the broadcasted stream consists of the content encrypted by control words and control messages. The latter each contain control words resulting from the encryption of the original control words with a local key. Each mobile equipment is first connected to a mobile network of the GSM (Global System for Mobile Communications) or UMTS (Universal Mobile Telecommunications System) type or another through which it is located by the management center. The mobile equipment receives from this center a cryptogram containing a local identifier corresponding to that of the nearest network cell to its geographical position. This cryptogram transmitted to the security module of the equipment allows the determination of one or more local keys that are defined as functions of the local identifier.

Problems solved by technology

The drawback of a too advanced standardization as that of OMA technology lies in the fact that additional protection measures are restricted especially when the conditional access system has been pirated by third parties.
This piracy causes damage that affects both the content supplier as well as the supplier of conditional access.

Method used

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  • Method for local conditional access for mobile equipments
  • Method for local conditional access for mobile equipments
  • Method for local conditional access for mobile equipments

Examples

Experimental program
Comparison scheme
Effect test

first embodiment

[0050] the local key (KL1, KL2) is determined by the mobile equipment when it connects to the mobile network (NET2) by means of localization data or more precisely an identifier of a cell (C1-ID, C2-ID) of this network transmitted by the management center (CG). The local key can be determined in several ways:

[0051] calculation carried out by means of an operation or a relatively simple mathematical function such as for example XOR (OR exclusive) or from a random number transmitted by the management center.

[0052] combination with a key specific to the mobile network or to a node of the latter provided either when the mobile equipment connects to the management center, or in response to a particular request by a short message SMS, for example.

[0053] the transmitted cryptogram can form the local key that can be used as it is, without intermediate calculation by the mobile equipment for decrypting the local control words.

[0054] To summarize, this local key is necessary for the decry...

second embodiment

[0057] the transmission key (TK) encrypting the control messages ECM can also depend on the broadcasting emitter. This configuration thus provides two security levels to be overcome in order to access the content broadcasted in the stream. When the mobile equipment is connected to the mobile network, it receives a management message EMM containing the local transmission key (TKL) or elements suited for determining said key (parameters, calculation functions). The message EMM is transmitted in general only if the local transmission key (TKL) is not available in the security module of the mobile equipment or after a key change. In fact, the validity of the latter, for example, can be limited to a certain period for a given emitter.

[0058] After having obtained this key (TKL) allowing the decryption of the control messages ECM, the mobile equipment determines the local key(s) (KL1, KL2) necessary for the decryption of the control words CW′ contained in the ECM messages. These local key...

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Abstract

A method is disclosed for conditional access to a digital data stream encrypted with at least one first control word and broadcasted via an emitter of a broadcasting network to at least one mobile equipment. The latter also is connected via a mobile communication network to a management center. The stream contains control messages encrypted with a transmission key and includes a second control word obtained by the encryption of the first control word with a local key. The method includes reception by the mobile equipment of at least one cryptogram via the mobile network, determination of at least one local key from the received cryptogram, and reception of a control message via the broadcasting network, decryption of the message and obtaining the second control word. The method further includes decryption of the second control word with the local key and obtaining the first control word and decryption of the data of the stream with the first control word

Description

TECHNICAL FIELD [0001] The invention concerns the domain of conditional access to a digital data stream broadcasted through a wireless channel and received by a plurality of mobile equipments, such as, for example, mobile telephones, PDAs (Personal Digital Assistants), portable digital television receivers or a portable computers. [0002] The broadcasted data is encrypted and can be received in plain text only by authorized equipment when the user has acquired the necessary rights. These rights, stored in a security module associated to the mobile equipment, consist of a set of keys that allow the decryption of the control words contained in control messages ECM (Entitlement Control Message) broadcasted in the audio data / video stream. [0003] A security module is considered as a tamper-proof device containing different encryption / decryption keys, information serving to identify a user on a network and the data that defines the rights purchased by the user for reception of a broadcaste...

Claims

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Application Information

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IPC IPC(8): H04L9/32G06K9/00G06F17/30G06F7/04H03M1/68H04K1/00H04L9/00H04N7/16H04H1/00H04H60/15H04N7/167
CPCH04H60/23H04H60/50H04N7/1675H04N21/25841H04N21/26606H04N21/64315H04N21/41407H04N21/42202H04N21/4405H04N21/44236H04N21/26609
InventorWENDLING, BETRANDLANDIER, OLIVIER
OwnerNAGRA FRANCE