Patent ID: 9077856
Filing Date: 2015-07-07
Classification: H04H,H04N

Abstract:
1. A method of conditional access to a digital data stream encrypted with at least one first control word and broadcast via an emitter of a unidirectional broadcasting network to at least one mobile equipment including a security module, the at least one mobile equipment also being connected via a bidirectional mobile communication network to a management center, said method comprising: receiving, by the mobile equipment, at least one cryptogram from the management center via the bidirectional mobile communication network, said broadcasted digital data stream including control messages encrypted with a transmission key and including a second control word obtained by a combination of the at least one first control word with a local seed; determining, by the security module of the mobile equipment, the local seed from the received at least one cryptogram, wherein the local seed depends on identifiers of network cells of the bidirectional mobile communication network that are geographically nearest relative to the mobile equipment, receiving, by the mobile equipment, a control message via the unidirectional broadcasting network, decrypting said control message and obtaining the second control word, and combining, by the security module of the mobile equipment, the second control word with the local seed, obtaining the first control word, and decrypting the broadcast digital data stream using the first control word.