Method for performing a sensitive data encryption with masking, and corresponding encryption apparatus and computer program product

Cryptographic circuitry masks sensitive data values. The masking includes extracting unique combinations of random mask values from one or more sets of random mask values. Each sensitive data value is masked using a respective unique combination. The unique combinations have a combination class greater than or equal to a determined integer corresponding to a protection-level against side-channel attacks, and a number of unique combinations greater than or equal to a number of the sensitive data values. A number of random mask values in the one or more sets of random mask values is based on the number of unique combinations and the class of the plurality of unique combinations.