Patent ID: 9730057
Date: 2017-08-08
CPC Classifications: G11B,H04L,H04N

Claim:
1. A management system for managing a population of decoders having access to transmitted data, each decoder being temporarily assigned to a position in a group of decoders and sharing a common broadcast encryption scheme, the management system being adapted to: revoke at least one decoder from the group; declare the position of the revoked decoder as vacated; renew a current group access key for the group using a global group addressed message comprising at least a next group access key encrypted using the broadcast encryption scheme so that only the decoders corresponding to non-revoked positions can decrypt it, whereby the at least one revoked decoder is incapable of correctly decrypting the global group addressed message, said group message being further encrypted by the current group access key; and reuse a position vacated by a revoked decoder by making said next group access key the current group access key and by marking the vacated position in the group as available and making another decoder a member of the group.