I don’t think that in the context of this discussion we care about which part is fun and which is not. Cryptanalysts often assume the knowledge of the cypher because it’s a realistic assumption that the attacker will have it. However there is a variety of techniques which assume only the availability of cyphertext or of both cyphertext and plaintext without knowing what the algorithm is.
we have a cypher that we cannot make sense of
Um, evidence? Did any professional cryptographer say that? Was a new class of cyphers invented? Should we use this cypher for important communications?
I don’t think that in the context of this discussion we care about which part is fun and which is not. Cryptanalysts often assume the knowledge of the cypher because it’s a realistic assumption that the attacker will have it. However there is a variety of techniques which assume only the availability of cyphertext or of both cyphertext and plaintext without knowing what the algorithm is.
Um, evidence? Did any professional cryptographer say that? Was a new class of cyphers invented? Should we use this cypher for important communications?