Cryptography: Theory and Practice, Third Edition (Discrete Mathematics and Its Applications)

Douglas R. Stinson's Cryptography: Theory and Practice is a mathematically intensive examination of cryptography, including ciphers, the Data Encryption Standard (DES), public key cryptography, one-way hash functions, and digital signatures. Stinson's explication of "zero-sum proofs"--a process by which one person lets another person know that he or she has a password without actually revealing any information--is especially good.

If you are new to the math behind cryptography but want to tackle it, the author covers all of the required background to understand the real mathematics here. Cryptography includes extensive exercises with each chapter and makes an ideal introduction for any math-literate person willing to get acquainted with this material.