given keylength, crack ciphertext by "ranking" the plaintext output

[evanrichter]

after guessing key values, there needs to be a way to figure out the best candidates for true key value.

we have access to the dictionary of plaintext words, so we can use character frequency with either strategy:

• just read every word from the dict and get a frequency. simple, words are sampled randomly so should be representative
• take the dict and build a plaintext of 10,000 words or so. then take character frequency of that

have a way to see how "close" a string of characters is to the expected character frequency distribution

[evanrichter]

Key:   abcdefgabcdefgabcdefgabcdefgabcdefgabcdefgabcdefgabcde
CT:    ______________________________________________________
PT:    this is normal plaintext attack at dawn blah blah blah

CT under the a's (assuming we got the keylength correct): _________
    for all the shift possibilities (0-26):
        apply the shift
        see what the character frequencies are
pick the shift amount that got you closest to the expected char frequency

[evanrichter]

• create a branch with skeleton code

[evanrichter]

skeleton code created! I imagine most of this code can go in this file on this branch