CRYPTOGRAPHY CIRCUIT PROTECTED AGAINST OBSERVATION ATTACKS, IN PARTICULAR OF A HIGH ORDER

摘要

The present invention relates to a cryptography circuit protected againstobservation attacks.The cryptography circuit comprises at least one register R (22) providing avariable x masked by the mask m, the masked variable being encrypted bya first substitution box S(1) in a cyclic manner. The circuit also comprises amask register M (23) delivering at each cycle a mask m 1, the transformationof m, the mask m being extracted from m1 before being encrypted by asecond substitution box S' (21), the new mask m' obtained on output fromthis box S' (21) is transformed into a mask m'1 before being stored in themask register M(23)The transformation consists of a bijection or a composition law making itpossible to reduce or indeed to cancel any high-order attack in accordancewith a model of activity of the registers R and M.The invention applies notably for the protection of cryptography circuitsagainst high-order observation attacks on installations based on masking.