METHOD OF SECURING A CALCULATION OF AN EXPONENTIATION OR A MULTIPLICATION BY A SCALAR IN AN ELECTRONIC DEVICE

A cryptographic operation includes calculating a multiplication of an element of an additively denoted group by a scalar. After two registers R0+R1, are initialized, iterations are carried out over the components Ki of the scalar K. If Ki of the scalar equals 0, then the value in register R1 is replaced by 2(R0+R1) If Ki equals 1, the value in register R0 is replaced by 2(R0+R1). At the end of the algorithm, the value of the register R0 is returned as the calculated result. This method poses the advantage of carrying out a calculation of multiplying by a scalar by carrying out only doubling and adding operations of the type 2(A+B).