NODE c6cf9375Index of Coincidence
Marc North <mnorth@netcom.com>Sun, 10 Mar 1996 05:35:06 +0800
I'm new to the mailing list, but I have grep'd tcmay's CP-FAQ and all
related FAQs for this, but have yet to find anything.
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.
Many thanks,
Marc
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| Marc North <*> mnorth@netcom.com <*> San Jose, CA. |
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NODE 18edeb7eRe: Index of Coincidence
"Rev. Ben" <samman-ben@CS.YALE.EDU>Mon, 11 Mar 1996 08:38:58 +0800
> 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
"If what Proust says is true, that happiness is the absence of fever, then
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NODE 0b8dae93Re: Index of Coincidence
"Perry E. Metzger" <perry@piermont.com>Sun, 10 Mar 1996 06:51:35 +0800
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