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Unformatted text preview: (b) Write the formula used by the Beaufort cipher to decipher the ith ciphertext letter c i . (c) Explain why Kasiskis method works to nd the length t of the key word for Beaufort just as it does for Vigen` ere. (d) Explain why the Index of Coincidence method works to nd the length t of the key word for Beaufort just as it does for Vigen` ere. 2. Suppose a Kasiski analysis identies these six pairs of repeated sequences in the ciphertext of a Vigen` ere cipher: Location of start of rst occurrence 10 21 37 49 58 72 second occurrence 34 65 109 105 162 132 What can you conclude about the length t of the key word used to encrypt the message? Explain your answer. 1...
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This note was uploaded on 03/03/2010 for the course CS 555 taught by Professor Wagstaff during the Spring '10 term at Purdue University Calumet.
 Spring '10
 Wagstaff

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