Patent ID: 8150029

Claim:
A method of detection of a disturbance of a calculation, by an electronic circuit, of a result of an integral number of applications of an internal composition law on elements of an abelian group, by successive iterations of different steps according to the even or odd character of a current coefficient of a polynomial representation of said integral number, the degree of which determines the number of iterations, each iteration comprising: initializing an expected value to a result of application of said composition law to first and second arbitrarily-selected numbers; in case of an odd current coefficient, updating at least one first variable intended to contain the result at the end of the calculation; and in case of an even current coefficient, updating a second variable by application of said composition law to the first and second arbitrarily-selected numbers and comparing the updated second variable with the expected value, the value of the updated second variable having no effect on the result of the calculation, wherein a lack of identity between the updated second variable and the expected value indicates a disturbance of the calculation, wherein in case there is no identity between the second variable and said expected value, the first variable is updated by a function modifying its value, before proceeding to the rest of the calculation, including executing, as long as all the significant coefficients of the polynomial representation of the integer have not been processed, at least the following operations: if the current coefficient is even: D=A(+)B, otherwise R=R(+)T and D=f(R); and in all cases: T=T(+)T, where (+) designates said composition law, R is said first variable initialized with the neutral element of the composition law to contain the final result, T is a third variable initialized with the value of the element to be submitted to the calculation, f is a function modifying its operand, and D is said second variable, A and B being digital values.