I just sent this to a2@well.sf.ca.us (arthur abraham) but after a finger attempt, I'm not so sure his account exists there anymore. On Wed, 20 Apr 1994, Matt Thomlinson wrote:

I'm reading through an old post of yours (gosh, 7 days from being a year old) regarding the clipper chip.

You laid everything out pretty carefully, but one thing your article doesn't seem to mention:

you've created the LEEF [L1|L2|IV] and when transmitted in the block, it looks like [encrypt(CV), checkword, L1|L2|IV], right? This is a 56+24+192 bit number ( = 272 bits).

My question: how often is this chunk sent? seems like you'd only need to send it once per call, but I'd think they'd send it every so often throughout a call, although this could cause problems for high-bandwidth digital uses, right?

Also, if someone could tell me if the checkword for the CV is encrypted along with the CV I'd be grateful. That is, is the packet [encrypt(CV,checkword), L1|L....] or [encrypt(CV), checkword, L1|L...] mt Matt Thomlinson University of Washington, Seattle, Washington. phone: (206) 548-9804 Check my home page -- ftp://ftp.u.washington.edu/public/phantom/home.html PGP 2.2 key available via email, or finger phantom@hardy.u.washington.edu