[42368] in Cypherpunks
Re: 80 bit security from 40 bit exportable products
daemon@ATHENA.MIT.EDU (Carl Ellison)
Thu Oct 26 12:42:13 1995
Date: Thu, 26 Oct 95 11:34:28 EDT
From: Carl Ellison <cme@TIS.COM>
To: jeffb@sware.com
Cc: cme@TIS.COM
Cc: cypherpunks@toad.com
In-Reply-To: Jeff Barber's message of Tue, 24 Oct 1995 16:05:59 -0400 (EDT) <199510252222.PAA16375@comsec.com>
>Even if you assume complete independence of key setup, if a successful
>decryption at each layer can be independently detected and verified
>(which seems likely in your example), there're only about 3 * (2 ^ 40)
>total operations in the worst case, NOT 2 ^ (3 * 40) operations needed
>to expose the plaintext. This is an effective 41.5 bits, not 120.
>
Of course. It comes down to whether each encryption step plans some known
plaintext to be used for brute force testing of any next layer.
