🚀 go-pugleaf

jdailey@dadd.ti.com (Jim Dailey) writes:

>So what are some of the methods used to attack an encrypted text, when the
>encryption method is unknown?

First you run frequency tests. This will tell you *immediately*
if a "reasonably sized" text was encrypted via *any* character
transposition cipher. 

Then you run statistical tests. These can identify the key length
in character based substitution ciphers.

Once you have the key length (unless it's long enough to have only been
used a *very* few times in the length of the message) you can start
solving the message as bunch of different *simple* substitution
ciphers.

I assume that there are methods for the "fancier" sort of cipher, but
for most folks, these do the job nicely. Alas, I misplaced the
disk with the programs on it and I haven't re-worked them from the
book again. 
-- 
Leonard Erickson		      leonard@qiclab.scn.rain.com
CIS: [70465,203]			 70465.203@compuserve.com
FIDO:   1:105/51	 Leonard.Erickson@f51.n105.z1.fidonet.org
(The CIS & Fido addresses are preferred)