Patent ID: 8971540
Filing Date: 2015-03-03
Classification: H04L

Abstract:
1. A computer-implemented method in a first entity for authenticating itself to a second entity by proving to the second entity that it is in possession of a full secret without sending the full secret to the second entity, the method comprising: receiving in the first entity an input from a user, the full secret having been divided into at least a first factor and a second factor and the input relating to the second factor of the secret; reconstructing in the first entity the full secret from at least the first factor and the input; and carrying out a calculation in the first entity using the reconstructed full secret and sending the results of the calculation to the second entity, wherein the results provide an input to a pairing calculation in the second entity, the secret corresponds to a point on an elliptic curve and the pairing calculation comprises a pairing on the elliptic curve wherein the method further comprises generating a random value x in the first entity, where x is lower than q; calculating A=H calculating another point U=xA on the elliptic curve in the first entity and transmitting ID receiving a random value y generated in the second entity, wherein y is lower than q, and wherein carrying out said calculation in the first entity using the reconstructed full secret and sending the results to the second entity comprises calculating a new point V=−(x+y)((s−α)A+αA) and sending the coordinates of V to the second entity, wherein the first factor corresponds to a point (s−α)A on the elliptic curve and the input comprises a value α, wherein the secret sA is issued by a trusted authority and has been obtained by the trusted authority by multiplying the point A, corresponding to the identity associated with the first entity, with a master secret s, and wherein the pairing calculation comprises a mapping where 1 and 2 are distinct and a is the order of the groups 1 , 2 , and T .