re: fast des

[Jason Zions <jazz@hal.com>]

>>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