A New Algorithm for Switching from Arithmetic to Boolean Masking

To protect a cryptographic algorithm against Differential Power Analysis, a general method consists in masking all intermediate data with a random value. When a cryptographic algorithm combines boolean operations with arithmetic operations, it is then necessary to perform conversions between boolean masking and arithmetic masking. A very efficient method was proposed by Louis Goubin in [6] to convert from boolean masking to arithmetic masking. However, the method in [6] for converting from arithmetic to boolean masking is less efficient. In some implementations, this conversion can be a bottleneck. In this paper, we propose an improved algorithm to convert from arithmetic masking to boolean masking. Our method can be applied to encryption schemes such as IDEA and RC6, and hashing algorithms such as SHA-1.