Breaking the Vigenere using frequency analisis

In this video I am showing you how to break the Vigenere cipher using frequency analysis. A brief description of the one time pad, or OTP, comes up, as well as the strengths of it.

To break the cipher you need to know about it's key length. After that number of letters you will have a repeating shift, thus the Vigenere cipher is just a number of substitution ciphers one after the other. This is why a one time pad is important: it creates a random, non repeating sequence of letters, the key in the case of the Vigener being it's greatest strength and weakness.