Los Angeles Math Circle

1/22 -- LAMC Beginners: Cryptoclub II

We will continue our study of cryptology with a look at the Vigenere cipher, once believed by many to be unbreakable. NOTE: For homework, complete sections 1-4. On Section 5, begin by numbering the cipher (the first one, which begins "KVX DOGRUXI OM R PHRH-KVBMRZ ...") in 123123123 fashion, and since there is a single letter R, guess either R=a or R=i for the ciphertext letters under number 1. Use your guess to decode the first three lines, but only the letters under number 1. We'll work on it more next week.