Abstract: In accordance with certain embodiments, a method for authenticating the identity of a user for granting resource access includes using a user device to obtain, in connection with an authorized user of the user device, authorized user authentication data (AUAD), using the user device to obtain, for a current user of the user device, current user authentication data (CUAD), comparing the CUAD with the AUAD, calculating a confidence index based upon the comparison of the AUAD with the CUAD, the confidence index reflecting a confidence level that the current user is the authorized user, and making the confidence index available to a resource provider to grant access to a resource if the confidence index is above a predetermined threshold