DrZaphod says:
Operating in a system expecting a clipper chip potentially restricts 'fish' for the CCW, where it is re-fed. The host system (to the clipper chip) is going to try and feed 10 bytes plush 3 bytes of a constant. Utilizing IDEA, the key is supposed to be 16 Bytes. The point being that dropping an IDEA chip in is not 'plug and play'. Couldn't one compress the IDEA key to 10 bytes and 3? The hardware wouldn't notice and since you'd be using an IDEA chip on both sides it could decompress and verify on the other end.
I think, that the original poster forgets the fact, that "Clipper" isn't just the Skipjack encryption algorithm implementation. Thus to compare Clipper to a chip that implements _only_ IDEA isn't very helpful. If one wants to imitate the Clipper - one will have to provide _all_ of the external functions it performs, and it doesn't matter at all, what encryption algorithm is implemented deeply inside. Of course, if the "internal" key is longer, than the "system standard" - you'd have to expand those 80 bits, let's say via running SHA over it... There are problems, but this isn't one of them (:-). -- Regards, Uri uri@watson.ibm.com scifi!angmar!uri N2RIU ----------- <Disclamer>
From owner-cypherpunks Thu Jan 27 03:47:32 1994