Patent ID: 8635460

Claim:
A method for masking a digital word by application of a random bijection, comprising: applying a first operation to said word, the first operation comprising acts of: selecting, by a computing device, a subset of said word, the selected subset comprising a plurality of successive bits and having a position and a size depending on a first random quantity; assigning, by the computing device, to each bit of the selected subset a state of a bit in the selected subset having a symmetrical position with respect to a middle of the selected subset; and concatenating unselected bits of the digital word with the assigned bits of the selected subset, to obtain a result of the first operation; applying a second operation to the result of the first operation, the second operation comprising a bit-to-bit combination by an XOR function of the result of the first operation with a second random quantity, to obtain a result of the second operation; and applying a third operation to the result of the second operation, the third operation comprising a circular permutation of the result of the second operation a number of times based on a third random quantity, to obtain a masked digital quantity.