[51766] in Cypherpunks
Re: Index of Coincidence
daemon@ATHENA.MIT.EDU (Perry E. Metzger)
Sat Mar 9 15:35:34 1996
To: Marc North <mnorth@netcom.com>
Cc: cypherpunks@toad.com
In-Reply-To: Your message of "Sat, 09 Mar 1996 11:35:55 PST."
<Pine.SUN.3.91.960309113033.18346B-100000@netcom12>
Reply-To: perry@piermont.com
Date: Sat, 09 Mar 1996 15:25:19 -0500
From: "Perry E. Metzger" <perry@piermont.com>
Marc North writes:
> I'm looking for detailed information on a statistical tool to aid in
> cryptanalysis called an "index of coincidence". I would appreciate it if
> someone could please explain what this is, how one builds such an index
> against a given ciphertext, and how it is valuable in the cryptanalysis of
> said ciphertext.
There is a fairly good general description in "The Codebreakers";
there is also a book by Friedman available from Agean Park Press that
covers the topic. I don't know of any public tools to do the work,
but it isn't very hard...
Perry
