[wyager]

Practically speaking, every face has to communicate, what, 20 bits of information, to avoid common doppelgängers via the birthday paradox? Probably even more. Very interesting.

People have proposed leveraging this to generate unique avatars, since you can just pick some random parameters for the arrangement of a stick figure face and it will probably look unique.

[Capt-RogerOver]

Openface (probably state-of-the-art currently? If I haven't missed anything) uses a 128-dimensional unit hypersphere to represent a face identity. They have likely optimized this, so it's the dimensionality that works well in practice, not too large, not too small. It's perhaps a bit bigger than it has to be, but it cannot be too big either because that would very likely lead to overfitting. So that's 128*sizeof(float) = 512bytes = 4096 bits of information. Kinda like an RSA private key :).