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Re: clipper pin-compatible chip
>From: [email protected] (Mike McNally)
>I don't think the idea proposed is to reverse-engineer the Clipper.
>Rather, the idea is that once you know the pin-out you can make an
>electrically-compatible (and, in important ways, software-compatible)
>replacement.
While the clipper chip and its CCEP brethern have chip specifications
that imply that key is supplied as long as a read flag is in a certain
state. The key for the clipper chip is 10 bytes of actual key plus
3 bytes of cryptographic check word (CCW), for a total of 13 bytes.
Operating in a system expecting a clipper chip potentially restricts
the keyspace. Non-centrally selected keys use the clipper chip to
'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'.