Renewable traitor tracing

A computer program product for traitor tracing, the computer program product comprising a non-transitory computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to perform a method comprising:

• receiving encrypted content at a receiver, the receiver having an associated plurality of sequence keys;
• receiving a sequence key block comprising link keys at the receiver, the sequence key block being formulated to cryptographically revoke sequence keys associated with one or more traitorous receivers;
• selecting a first sequence key from the plurality of sequence keys;
• determining a first link key by applying the first sequence key to the sequence key block;
• traversing the sequence key block using the first link key and the remaining plurality of sequence keys, wherein traversing the sequence key block comprises:
• decrypting a first subset of the sequence key block using the first link key to obtain a second link key from the sequence key block,
• decrypting a second subset of the sequence key block with the second link key to obtain a third link key from the sequence key block, with which decryption of the sequence key block is repeated;
• and
• determining from the traversal that at least one of the remaining plurality of sequence keys has been revoked.