Patent ID: 8156336

Claim:
A method for determining whether a first device and a second device both possess a value h, the method comprising: receiving and storing a product R D from the first device, wherein R D is a product of a random value r D and a public key value P; receiving and storing a product R B and a challenge value e D from the second device, wherein R B is a product of a random value r B and the public key value P; transmitting the challenge value e D to the first device; receiving and storing a value y D and a challenge value e B from the first device, wherein a first expression involving the value y D , the random value r D and the challenge value e D has a value equivalent to a product hP of the value h and the public key value P; transmitting the challenge value e B to the second device; receiving and storing a value y B from the second device, wherein a second expression involving the value y B , the challenge value e B and the random value r B has a value equivalent to the product hP; and determining that the first device and the second device are both in possession of the value h when a condition y B P+e B R B =y D P+e D R D is satisfied.