Human Verification Protocol (HVP)
This is a protocol designed to prevent online impersanation.
It is not a computer protocol. It is a human protocol.
It requires cooperation from both parties.
The human that is in the same physical location as the target.
The thing to verify belongs to the verifier. Often the verifier's face.
Aquire image of target
For additional insurance, this step can be performed before the target is informed that this protocol is being used.
The key consists of a sequence of numbers between zero (0) and five (5) (inclusive). More numbers means less chance the key has been used before. With four (4) numbers, there are 625 possible keys. Keys can easily be generated by repeatedly rolling a standard six (6) sided die and subtracting one from the result each time.
Have verifier count off keys
This will typically be done over video, with standard finger counting. The target must be in view the entire time. For additional security, this should be done live (eg. in a video call).