Provides a base for all Shiro Hash algorithms with support for salts and multiple hash iterations. <p/> Read <a href="http://www.owasp.org/index.php/Hashing_Java" target="blank">http://www.owasp.org/index.php/Hashing_Java</a> for a good article on the benefits of hashing, including what a 'salt' is as well as why it and multiple hash iterations can be useful. <p/> This class and its subclasses support hashing with additional capabilities of salting and multiple iterations via overloaded constructors.