METHOD FOR PROVIDING ACCESS CONTROL TO MEDIA SERVICES
First Claim
1. A method for allowing a receiving device comprising a security module to access media services encrypted under at least a control word, said access being subject to at least the presence of a right in said security module, the method comprising:
- receiving an entitlement management message comprising at least said right and verification data;
processing the entitlement management message at least to check the verification data;
during the processing of said entitlement management message, building a signature value through a plurality of predetermined operations at intervals within said processing step;
deriving a digest (KRi) from at least a part of said signature value;
in response to said entitlement management message being valid, recording the right into a rights database together with the digest;
receiving an entitlement control message (ECM) comprising an encrypted control word and an access condition referring to said right;
processing said entitlement control message at least to verify whether the right referred to by said access condition is present in the rights database;
retrieving a digest corresponding to the right referred to by the access condition; and
decrypting the encrypted control word using said digest.
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Accused Products
Abstract
The present invention proposes a solution to prevent a program flow in a processing unit from being modified with respect to an intended program flow, thereby ensuring that important steps such as verifying or authenticating are not bypassed. The invention is particularly aimed at security modules within receiver/decoders in a pay-TV system and involves performing a set of predetermined operations during the processing of entitlement management messages and/or entitlement control messages, said operations being redundant with respect to the normal processing of said messages while leading to the calculation of keys which can then be used to verify that the intended program flow has been respected.
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Citations
10 Claims
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1. A method for allowing a receiving device comprising a security module to access media services encrypted under at least a control word, said access being subject to at least the presence of a right in said security module, the method comprising:
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receiving an entitlement management message comprising at least said right and verification data; processing the entitlement management message at least to check the verification data; during the processing of said entitlement management message, building a signature value through a plurality of predetermined operations at intervals within said processing step; deriving a digest (KRi) from at least a part of said signature value; in response to said entitlement management message being valid, recording the right into a rights database together with the digest; receiving an entitlement control message (ECM) comprising an encrypted control word and an access condition referring to said right; processing said entitlement control message at least to verify whether the right referred to by said access condition is present in the rights database; retrieving a digest corresponding to the right referred to by the access condition; and decrypting the encrypted control word using said digest. - View Dependent Claims (2, 3, 4, 5)
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6. A receiving device comprising a security module to access media services encrypted under at least a control word, said access being subject to at least the presence of a right in said security module, said security module comprising:
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a processor; and a database connected to the processor; wherein the processor is configured to perform the steps of; receiving an entitlement management message comprising at least said right and verification data; processing the entitlement management message at least to check the verification data; during the processing of said entitlement management message, building a signature value through a plurality of predetermined operations at intervals within said processing step; deriving a digest from at least a part of said signature value; in response to said entitlement management message being valid, recording the right into a rights database together with the digest; receiving an entitlement control message comprising an encrypted control word and an access condition referring to said right; processing said entitlement control message at least to verify whether the right referred to by said access condition is present in the rights database; retrieving the corresponding digest corresponding to the right referred to by the access condition; and decrypting the encrypted control word using said digest. - View Dependent Claims (7, 8, 9, 10)
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Specification