CDMF [was Re: Columbia crypto box]

Anton Stiglic astiglic at
Wed Feb 12 11:58:45 EST 2003

----- Original Message -----
From: "Bill Frantz" <frantz at>

> through the 40 bit key space.  (IIRC, basically what the device did was
> reveal 16 bits of a DES key.)

I can't find a description of it on the web (I had it on a paper somewhere
I don't have access to it now),
but I think that what it does is encrypt the intial 56-bit key (64 bits with
additional parity bits) using a fixed value 56-bit key.  Then, given the
result, it would substitute 16 (non parity) bits with fixed values and
the result so that it had correct parity, effectively tranforming keys with
random bits to only 40 random bits.  (maybe I'm recalling wrongly however
I think it was something like that...)

Can you do E-D-E with this, using double-length keys, to effectively get a
strength of 80 bits? (at a first glance, I don't see what would prevent you
from doing this..).
If it's a library that you were exporting, with an API for encryption and
nothing would prevent someone from using such a library to do strong


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