[51790] in Cypherpunks
Re: Index of Coincidence
daemon@ATHENA.MIT.EDU (Rev. Ben)
Sat Mar 9 20:30:33 1996
Date: Sat, 9 Mar 1996 20:04:01 -0500 (EST)
From: "Rev. Ben" <samman-ben@CS.YALE.EDU>
To: Marc North <mnorth@netcom.com>
Cc: Den of CryptoAnarchists <cypherpunks@toad.com>
In-Reply-To: <Pine.SUN.3.91.960309113033.18346B-100000@netcom12>
> 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.
Given a ciphertext X with discrete components x[1], x[2], ... x[n], I[c]
is the probability that two random elements of x are identical.
Ben.
Ben Samman..............................................samman@cs.yale.edu
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