Re: Plaintext

Darrell Kindred (dkindred@cmu.edu)
Wed, 2 Jul 1997 18:27:36 -0400


Nelson Minar writes:
> >In most real world applications, you'll have at least some
> >information about what's inside, whether it's time-stamps, or
> >headers, on a Word document, or whatever.
>
> This is basic canon for cryptanalysis, but I'm not sure I believe it.
> PGP, for instance, does its best to compress the data up to maximum
> entropy to prevent analysis on the plaintext. What do you do in that
> circumstance?

Well, in the worst case, you can just try a decryption key,
then see if the result uncompresses properly, then see if
the uncompressed text looks like what you expected to see.
Compressing plaintext may complicate the brute-force attack,
but it doesn't prevent it.

- Darrell