A method for determining an authentication score for use in exchanging information between a first and a second device. The method comprises at the first device: determining a first authentication score associated with a first information exchange session between the first and second devices; determining a second authentication score associated with a second information exchange session between the first and second devices, the second information exchange after the first information exchange; combining the first and second authentication scores to create a combined score; responsive to the first authentication score, generating an encryption key for encrypting the combined score, wherein the encryption key is known by the first and the second devices; and encrypting the combined score to generate a dynamic pairing code.