References
Cryptology

M. Gardner, Codes, Ciphers, and Secret Writing. Dover
Publications, Inc. New York 1984.

A. Young, Mathematical Ciphers: From Caesar to RSA.
Mathematical World, Volume 25. American Mathematical Society
2006.
Number Theory

I. Niven, H. Zuckerman, and H. Montgomery, An Introduction to the
Theory of Numbers, 5th ed. Wiley 1991

K. Rosen, Elementary Number Theory, 5th ed. Addison Wesley
2004.
This work was made possible through a grant from the National
Science Foundation.