Patent ID: 7110546

Claim:
A secure communication system including a source device and at least one sink device; information being transferred from the source device to the at least one sink device in a communication session including the transfer of a plurality of packets from the source device to the at least one sink device; each packet including a data field for transferring a portion of the information; the source device including: a key generator for, at the initiative of the source device, generating an active session source key in a predetermined sequence of source session keys Ksource i ; an encryptor for encrypting at least part of the data field of a packet under control of the active source session key; the encrypted part of the data field including a sub-field designated as a key check block field that contains a key check block such that a plain-text form of the key check block is a data block agreed between the source and sink devices before starting the transfer of the information; the at least one sink device including: a key generator for generating a plurality of candidate sink session keys in a predetermined sequence of sink session keys Ksink i , where for each index i in the sequence the respective sink session key Ksink i corresponds to the respective source session key Ksource i ; a decryptor for decrypting at least part of the data field of a received packet under control of a sink session key; a key resolver operative to determine which of the candidate sink session keys corresponds to the source session key used to encrypt the encrypted part of a received packet, by causing the decryptor to decrypt the data in the key check block field of the received packet under control of a different one of the plurality of candidate sink session keys until a valid decryption result is found; and to cause the decryptor to decrypt a remaining encrypted part of the data field of the packet under control of the candidate sink session key which produced the valid decryption result.