1. A method for determining the liveness of the face of a user, said method comprising: acquiring a first image of a face of a user with an interface; providing an instruction to the user to reorient the user's head to a new position with an output device; acquiring a second image of the face of the user with the interface; determining if the instructed reorientation was performed with a processor connected to the interface by comparing the first image and the second image; identifying a plurality of facial feature points on the first image and the second image; identifying displacements of the facial feature points between the first image and the second image; fitting the displacements of the facial feature points to a three-dimensional surface model; and determining whether the first image and the second image are authentic with the processor based on said fitting of the displacements of the facial feature points to the three-dimensional surface model.