Retinal photon
Rétine par les photons

(2017 Apr) It is known that the eye’s scotopic photodetectors, rhodopsin molecules and their associated phototransduction mechanism leading to light perception, are efficient single photon counters. We here use the photon counting principles of human rod vision to propose a secure quantum biometric identification based on the quantum-statistical properties of retinal photon detection. The photon path along the human eye until its detection by rod cells is modeled as a filter having a specific transmission coefficient. Precisely determining its value from the photodetection statistics registered by the conscious observer is a quantum parameter estimation problem that leads to quantum secure identification method. The probabilities for a false positive and a false negative identification of this biometric technique can readily approach 10^-10 and 10^-4, respectively. The security of the biometric method can be further quantified by the physics of quantum measurements. An impostor must be able to perform quantum thermometry and quantum magnetometry with energy resolution better than 10^-9~, in order to foil the device by non-invasively monitoring the biometric activity of a user.

• Original paper (2017 Apr): Quantum Biometrics with Retinal Photon Counting / M. Loulakis, G. Blatsios, C. S. Vrettou, and I. K. Kominis

(my explanation -less complicated I hope-)

• It is possible to construct a kind of sensitivity map of your retina, thanks to its extraordinary sensitivity: a few photons are enough.
• Enrolment: in the present proposal, a light source sends around 6 photons successively at some locations, and Alice says if she sees something or not. At the end of this process, we have a sensitivity map, which is the biometric template.
• Recognition: the system chooses arbitrary locations. For instance, we know that at some location, it is sensitive, so we send the shape of a "2". Alice must see that, but Eve has very few chances to see this shape. We can repeat this process with some unsensitive locations: Alice must see nothing, but Eve is likely to see something. Repeating this process will reduce the chances to make a mistake.

This is a very attractive biometric modality, because it involves the brain, and so we should have quite a natural aliveness detection -at first sight- (if I can say that, speaking of retina :)

From a security point of view, there are some important details:

• The template must be cyphered. If Eve knows the template, then it will be possible to use a simple camera (photodetector in the paper) instead of an eye to look at the sent pattern, and decide if we should see something or not. The paper indicates that we could force Alice to answer, but this is not so useful, just steal the template.
• As a result, we must be sure that we have a real eye in front of the system: this is not only a simple photon source.
• The paper indicates that the sent pattern sequence could be public: this is generally a mistake. In any cryptographic system, when you want to check for a secret key, you MUST use a true random number generator. If you know the sequence, then it is possible to replay it, and then obtain some information about the key... (here the template).

Unprecedented level of security : maybe or maybe not. Yes if some aliveness detection is added to check that the source is sending photons to a real eye.

That said, I have been impressed by this proposal, likely one of the most potentially secure biometric modality I have ever seen, because the brain is involved (and I think I know a little bit about this topic :).

The tongue and its taste sensors, connected to the brain, should work the same... but well, not that pratical.