From: uri@watson.ibm.com
Date: Thu, 27 Jan 94 09:12:12 PST
To: drzaphod@brewmeister.xstablu.com (DrZaphod)
Subject: Re: clipper pin-compatible chip
In-Reply-To: <m0pPPCs-0003DXC@brewmeister.xstablu.com>
Message-ID: <9401271709.AA12076@buoy.watson.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain


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
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<Disclamer>


From owner-cypherpunks  Thu Jan 27 03:47:32 1994