I recommend my own book, Applied Cryptography (John Wiley & Sons, 1996), as a good place to start. Then read The Codebreakers , by David Kahn (Scribner, 1996). After that, there are several books on computer cryptography, and a few others on manual cryptography. You can subscribe to my free e-mail newsletter at or by sending a blank e-mail message to . It’s a fun field; good luck.