Looking for unique biomarkers beneath the surface of our skin is a clever way of identifying us—you can change your hairstyle or wear colored contacts, but it’s really tricky to rewire your vein structure.

Using biometrics to recognize and authenticate someone also has an added layer of security in that it requires that they are living, since these systems look for both structure and movement.

But for those who are concerned that one bio-identifier isn’t secure enough, scientists at the National Taiwan University of Science and Technology developed a kind of two-factor authentication method that first looks at skeleton topologies and then finger vein patterns.