1. A method of processing calculations for algorithms involving Galois Field arithmetic, the method comprising the steps of: mapping one or more source arithmetic operations in Galois Field GF(2 n ) into sets of corresponding arithmetic operations for a plurality of respective isomorphic composite Galois Fields GF((2 p&lsqb;1&rsqb; ) p&lsqb;2&rsqb; )... ) p&lsqb;v&rsqb; ), for one or more of each unique decomposition of n into p&lsqb;i&rsqb;s such that &pgr; v i&equals;1 p&lsqb;i&rsqb;&equals;n; evaluating, for each respective set of corresponding operations, a field cost function relating to an implementation of the source arithmetic operations with the set of corresponding arithmetic operations; and selecting one of the sets of corresponding arithmetic operations as a target set of arithmetic operations, based on calculated results of an aggregate cost function based on the field cost function for each of the respective sets.