Patent ID: 8543822

Claim:
A method to be performed by a first device that possesses a value h for determining whether a second device possesses the value h, the method comprising: generating a product R D and transmitting the product R D to a third device, wherein R D is a product of a random value r D and a public key value P; receiving from the third device a challenge value e D that was received by the third device from the second device; receiving from the third device a product R B that was received by the third device from the second device, wherein R B is a product of a random value r B and the public key value P; obtaining a challenge value e B and transmitting the challenge value e B to the third device; receiving from the third device a value y B that was received by the third device from the second device; calculating y B P+e B R B to obtain a first result; calculating hP to obtain a second result; comparing the first result to the second result; and determining that the second device is in possession of the value h when the first result is identical to the second result, wherein the public key value P generates a prime subgroup of the group E(F q ) of order p, wherein F q is a finite field of prime order q, wherein the random values r D and r B are between the number 1 and the number (p−1), and wherein the challenge values e D and e B are between the number 1 and the number (p−1).