Java Number Cruncher: The Java Programmers Guide to Numerical Computing

The classes BigInteger and BigDecimal , which are in the java.math package, are fully described by the Java documentation supplied by Sun Microsystems, Inc.

Clawson, Calvin C., Mathematical Mysteries: The Beauty and Magic of Numbers , New York: Plenum Press, 1996.

Graff, Jon C., Cryptography and E-Commerce , New York: John Wiley and Sons, 2001.

Knudsen, Jonathan, Java Cryptography , Sebastapol, CA: O'Reilly, 1998.

Clawson contains a brief but good introduction to public key encryption in Chapter 9. Graff and Knudsen are good introductory texts to cryptography; the latter is Java-specific.