Index of Coincidence

[Marc North]

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 at netcom.com  <*>  San Jose, CA. |
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