What's the received view on the worth of the parity bit in DES as a checksum? It can catch single bit errors in a byte, no double errors in a byte, and... (it gets more complicated after that). Most checksum mechanisms have a somewhat rationally chosen set of things that they do and don't catch (e.g. bursts). But while you might make a case for the DES approach, it would seem to be after the fact. By utilizing those 8 bits to deal with some global key errors you could presumably do better. It just seems like they threw it in without really caring. But that seems unlikely. Anyone know? Mike