[Fwd: Cylink can export 128-bit DH?]

[Perry E. Metzger]

Mike Duvos writes:
> frantz at netcom.com (Bill Frantz) writes:
> 
>  > Most cryptographic experts recommend Triple DES, encrypting
>  > the data 3 times with 3 different keys.
> 
> It's actually encrypted three times with two keys comprising
> 112 bits of keyspace, using a decrypt on one key sandwiched
> between two encrypts using the other.  This prevents a "man
> in the middle" attack, which would be possible if only two
> DES encryptions were used, one for each key.

Many 3DES implementations actually do use 3 different
keys. Surprisingly, the strength of 3DES with 3 keys is around the
strength you would naively expect 3DES with 2 keys to have, and 3DES
with 2 keys is slightly weaker than you would expect...

.pm