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