Digital message e.g. paid audiovisual program, transmitting system for wireless broadcasting network, has decryption modules distributed in specific groups, and memories of each module of same group storing decryption key specific to group

摘要

The system has electronic decryption modules (17) distributed in k+1 decryption module groups whose composition is secret, where k is collusion threshold. Each module has memories (21, 22) to store information. The memories of each module of a same group contain a decryption key specific to the group. The different decryption keys specific to the groups permit the decryption of a same encrypted message for the group and avoid the decryption of an encrypted message for another group. An electronic encryption module (10) encrypts a digital message for a particular decryption module group. An independent claim is also included for a method for transmitting a digital message.