Patent ID: 9400636
Filing Date: 2016-07-26
CPC Classification: G06F,H04L

Claim Text:
1. An apparatus for calculating a result of a scalar multiplication of a reference number with a reference point on an elliptic curve, comprising: a random number generator comprising electric circuitry and configured to generate random bits; and a processor configured to calculate the result of the scalar multiplication based on a Montgomery ladder algorithm involving a loop over every bit of the reference number, the processor comprising a first auxiliary variable storing a first interim result representing an integer multiple of the reference point or a coordinate of an integer multiple of the reference point and a second auxiliary variable storing a second interim result representing another integer multiple of the reference point or a coordinate of another integer multiple of the reference point, wherein the processor is configured to, per loop i of the Montgomery ladder algorithm, swap a value stored by the first auxiliary variable and a value stored by the second auxiliary variable, if a swap condition is fulfilled, and controlled via a computation condition which at least depends on an i wherein at least one of the swap condition and the calculation condition depends on the i wherein a result of scalar multiplication is determinable from values stored by the first and second auxiliary variables after the loop over every bit of the reference number.