Re: DE-crypting (trivial case)

[cort <cort@ecn.purdue.edu>]

> I was wondering if anyone knew of software that
> does decryption of weakly encrypted messages,
> i.e., similar to ROT13, but perhaps ROT(x) where
> 0<x<26?  Or maybe a bit more sophisticated, but
> not even at the single DES level?

There is stuff to be had.  Look on the ftp sites (especially ripem.
msu.edu).

crypt200 by John K. Taber helps solve transposition and substitution
ciphers.

> Also...anyone know of any histogram software?
> i.e., I input a file, it counts how many
> letters of each type, and outputs it in a
> table and/or a graph?

Again, lots of statistics gathering software in the crypt directories
lying around the internet.

> If not, I'll have to (horrors!) write code!

I have examined a couple of these software packages and found some
of them very powerful.  However, all I have seen are interactive.
I want a pipe (ciphertext in; plaintext out).  This is completely
feasible for large classes of substitution/transposition ciphers.

I have ideas and _some_ code.

Some of the concepts to look for include isomorphisms and cross
reduction.

Good luck!

Cort.