The base class for hashing algorithms in the Java programming language. Implementations of MessageDigest algorithms must extend this class and implement all the abstract methods. The integration of this algorithm into the programming language standard libraries is an example of how higher-level programming languages include security-aware programming features enabling programmers to write better, more secure software. Sun Microsystems, Inc. Overview Package. [Online, 1999.] Sun Microsystems, Inc. Website. http://java.sun.com/products/javacard/htmldoc/javacard/security/ MessageDigest.html.