# Re: How do I apply the index of coincidence?

*From*: "T" <t1x.arnold@xxxxxxxxx>*Date*: 12 Mar 2006 07:38:08 -0800

Hmmm. Ok. So what is the first step in determining the plaintext from

the ciphertext "OPKWWECIYOPKWIRG"? If I understand the process

correctly, the key length must be determined.

On slide 35 it looks like the IC must be calculated to find likely

values of key length. The IC I get for "OPKWWECIYOPKWIRG" is

0.0583333333333. From slide 35 it appears that the likely key length is

2. Am I on the right track?

If I have this right so far, the ciphertext must be split into two

alphabets.

Alphabet 0:OKWCYPWR

Alphabet 1:PWEIOKIG

Now I'm stuck on determining the key. Any suggestions on how to

determine the key? Thanks!

.

**Follow-Ups**:**Re: How do I apply the index of coincidence?***From:*Xcott Craver

**Re: How do I apply the index of coincidence?***From:*Xcott Craver

**References**:**How do I apply the index of coincidence?***From:*T

**Re: How do I apply the index of coincidence?***From:*Xcott Craver

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