Patent ID: 8762723

Claim:
A method for establishing a secure communication session between a first device and a second device, wherein the first device comprises a physical unclonable function (PUF) element, the method comprising, performed at the second device: generating a second part of a challenge value; signing the second part of the challenge for signature verification at the first device and transmitting the signed second part of the challenge to the first device; receiving an encryption of a response from the first device representing a use of the challenge as an input to the physical unclonable function element at the first device; decrypting the encrypted response; determining a predicted response to the challenge, and determining if the decrypted response sufficiently matches the predicted response; generating a symmetric key based on the decrypted response; and using the symmetric communication key for communication with the first device; wherein determining if the decrypted response sufficiently matches the predicted response comprises computing a similarity between a plurality of parts of the decrypted response and a corresponding plurality of parts of the predicted response.