A user can be challenged to provide at least one randomly selected biometric attribute. The randomly selected biometric attribute input by the user is automatically compared to a plurality of biometric attributes of the user contained in a user profile. The user can then be authenticated if the randomly selected biometric attribute input by the user matches at least one of the plurality of biometric attributes of the user contained in the user profile. Biometric attributes analyzed according to the methods and systems of the present invention, include, but are not limited to, for example, fingerprints, iris, retina, and/or tissue characteristics, such as skin morphology, skin layer thickness, collage density and orientation, tissue hydration, optical patent length differences, etc.