From: Jason Zions <jazz@hal.com>
Date: Thu, 17 Jun 93 14:13:23 PDT
To: cypherpunks@toad.com
Subject: re: fast des
Message-ID: <9306172113.AA10922@jazz.hal.com>
MIME-Version: 1.0
Content-Type: text/plain



>>Usually the limiting factor is examining the <ostensibly> decrypted data
>>for statistically significant patterns indicating that you have the
>>correct key.  
>
>If you know that your plaintext is 7-bit ASCII, then you can reject if you
>see too many 8th bits set. [ ... ]  Hint for implementors: don't allow such
>easy bit correlations in your plaintext.

Run your plaintext through compress first; remove the compress header; then
encrypt. Compression will screw up character frequencies (and use all eight
bits) enough to make automated detection of a successfully-broken encryption
really darn hard. Especially if you keep changing compression technology
each message.

Jazz