ENHANCED NATURAL MONTGOMERY EXPONENT MASKING

摘要

A method and apparatus for masking messages subject to exponentiation in a secure cryptographic device subject to a chosen-message attack for the purpose of discovering secret exponent information through non-invasive physical testing of the cryptographic device. Through the use of Montgomery arithmetic, a random multiplicative factor is applied to the input message, and can be easily removed without having to compute the inverse of the random factor, as is necessary with prior-art masking techniques. This masking complements and enhances the natural masking inherent in the use of Montgomery arithmetic. The method of the persent invention is ideally suited to Montgomery arithmetic processors, but is not limited thereto, and can be used in combination with other security techniques.