The following was encrypted using the Vigenere cipher. Determine the length of the keyword. First use the Kasiski method to make a conjecture about the key length by finding several trigraphs and factoring the distances between them.Assuming k is the length of the keyword, now write a program that finds the frequency of letters A... Z for every letters in positions 0, k, 2k, etc. in the ciphertext. This is exactly what we did in the lecture during the cryptanalysis. The output looks like this for example: [10,0,0,1,1,3,7,0,0,5,7,3,2,2,0,0,1,0,4,1,2,3,10,0,1,6], which means that letter A appeared 10 times, letter B appeared 0 times and ... . These numbers are different from the numbers you will get. You should have k output vectors of length 26. The second shows frequency of [A,...,Z] of the letters appearing in positions 1, k+1, 2k+1, etc. The third shows the frequency of the letters appearing in positions 2, k+2, etc. Now write down those histograms in your answer sheet and underline every number that is 6 or more. Use the fact that the distances between A, E, T and A in the alphabet are 4, 15, and 7 to decide how much each shift was. Write down all possible shifts for each histogram. Determine the keyword.

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