A method and apparatus for increasing performance of a multiplication operation in a processor. The processor's instruction set includes multiply instructions that can be used to accelerate modular exponentiation. Prior to issuing a sequence of multiply instructions for the multiplication operation, a multiplier register in a multiply unit in the processor is loaded with the value of the multiplier. The multiply unit stores intermediate results of the multiplication operation in redundant format. The intermediate results are shifted and stored in the product register in the multiply unit so that carries between intermediate results are handled within the multiply unit.