Cryptology, the science of secret writing, is a great way to introduce students to different areas of mathematics such as number theory, linear algebra, probability and statistics. Cryptology consists of two branches: cryptography and cryptanalysis. Cryptography is the science of designing techniques for encrypting and decrypting a message. Cryptanalysis is the science of recovering plaintext (the original unencrypted form of a message) from ciphertext (the secret form of the message after encryption) without knowledge of the process used for encryption and decryption. One of the most famous, private-key cryptosystems is the Vigenere Cipher. Encryption and decryption using the Vigenere Cipher was originally described in terms of a table known as the Vigenere Square and a secret keyword. Like many other cryptosystems, it is quite easy to describe this cryptosystem mathematically using basic properties of modular arithmetic. The purpose of this paper is to show students how the TI-83 graphic calculator can perform the computations needed to implement the Vigenere Cipher.