A Vigenére cipher appeared in the final exam of Cryptography. It will be solved here, step by step, demonstrating a proposal of a general solution to a polyalphabetic substitution cipher. A few valuable tools of breaking Vigenére will also be presented. Topics that will be discussed: frequency analysis, Kasiski method of estimating Vigenére key-length, data-distribution etc.

The cipher

Hint: the string “bhwzkohxool” occurs twice in the text.

Solution to Vigenére cipher

(2 b continued…)