G. Mark

July 28, 2011 at 11:27 am

Interesting observation about “shifting” the keys for ciphertexts 2 and 3. That wasn’t necessary if you feed the ciphertext into a Vigenère three times with the three keys. The offset is zero for each, beginning with the start of the message, so that the transition from one key to the other is not dependent upon the ciphertext length. Again, simplify. :)

BTW, for the winner of the crypto contest (Joel Kerr), I sent an NSA challenge coin and an official NSA reproduction of a Civil War field cipher wheel that would have been used for encoding/decoding messages during the war. – G. Mark