re off the shelf cheap des keyseach machine in article apr silverton berkeley edu djb silverton berkeley edu d j bernstein writes in article apr ulysses att com smb research att com steven bellovin writes and key size is one of the things that can be verified externally gee say they feed the bit key through snefru and take the first bits of the result then use those bits as the real key how do you figure out that each key is one of equal keys you can try a birthday attack but if the key can be changed only once a second then you will need several lifetimes to get reliable statistics you re right and i retract the suggestion still i wonder that there are only bits of key information should in principle be detectable maybe some variant of the tests rivest et al did to demonstrate that des was probably not a group it should make an interesting paper a black box analysis of a cryptosystem
