Patent ID: 7400723

Claim:
A method for securing a cryptographic process that generates output data from input data and a private key, the method comprising: a key scheduling process comprising a plurality of derived key scheduling steps to each provide an updated derived key from a previously derived key computed during a preceding derived key scheduling step, a first updated derived key being obtained from the private key; masking the private key, prior to the key scheduling process, so that each updated derived key is different for each key scheduling process; wherein, during the masking step, a randomly chosen masking parameter is mixed with the private key, to provide a masked private key, the first updated derived key being computed from the masked private key during a first derived key scheduling step; and performing a plurality of computation steps, each using an updated derived key, and an unmasking step is executed after each computation step to eliminate a contribution of the masking parameter on a result of the previous computation step.