Renewable traitor tracing

A computer program product for preventing re-use of compromised sequence keys in a broadcast encryption system, the computer program product comprising a non-transitory computer readable storage medium having computer readable program code embodied therewith, the computer readable program code comprising computer readable code for:

• receiving a distributed protected file and a sequence key block at a receiver, the sequence key block being formulated to cryptographically revoke traitorous receivers;
• selecting a first Sequence Key from a plurality of Sequence Keys, the plurality of Sequence Keys being associated with the receiver, and the plurality of Sequence Keys being related by the sequence key block;
• determining by cryptographic testing that the first Sequence Key is compromised,
• cryptographic testing comprising applying the first Sequence Key to the sequence key block;
• determining that at least one additional Sequence Key is available;
• traversing the sequence key block to select a second Sequence Key from the plurality of sequence keys;
• determining by cryptographic testing that the second sequence key is compromised,
• cryptographic testing comprising applying the first Sequence Key to the sequence key block;
• traversing the remainder of the sequence key block and thereby determining that no uncompromised sequence keys can be determined from the sequence key block
• identifying the receiver as traitorous based on the lack of uncompromised sequence keys.