[prev in list] [next in list] [prev in thread] [next in thread] 

List:       linux-crypto
Subject:    Re: (AES) loopback crypto questions
From:       Henry Spencer <henry () spsystems ! net>
Date:       2001-07-11 21:30:31
[Download RAW message or body]

On Wed, 11 Jul 2001, Michael H. Warfield wrote:
> ...A "double DES"
> would only have the equivalent strength of roughly 57 bits (for two
> rounds of 56 bit DES) where as 3-DES defeats the meet in the middle
> attack resulting in 112 bit strenght for EDE two key mode or 168 bits
> where all three keys are independent.

Small correction:  it's 112 bits either way.  Even with three independent
keys, a meet-in-the-middle attack remains possible, but one side of the
attack has to deal with a pair of DES keys rather than just one.  The
difference between 56 and 112 is between costs of the order $100k and
costs that even NSA (probably) can't afford. 

                                                          Henry Spencer
                                                       henry@spsystems.net


Linux-crypto:  cryptography in and on the Linux system
Archive:       http://mail.nl.linux.org/linux-crypto/

[prev in list] [next in list] [prev in thread] [next in thread]