Index of Coincidence
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 -- .--------------------------------------------------------. | Marc North <*> mnorth@netcom.com <*> San Jose, CA. | `--------------------------------------------------------'
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
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 I will never know happiness. For I am possessed by a fever for knowledge, experience, and creation." -Anais Nin Want to give a soon-to-be college grad a job? Mail me for a resume
participants (3)
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Marc North -
Perry E. Metzger -
Rev. Ben