# Identification

I am reading Jim Harper’s book Identity Crisis and got the inspiration to draw this simple chart of identifiers that can be used for multi-factor authentication.

Combinations of these identifiers can be used to increase the certainty in any authentication scheme (computer based or not).
As an example, if the probability of identifying someone using the hair color (something you are, biometric) is 1 in 10 ($I_1 = {{1} \over {10}}$) and the probability to identify him based on his name (something assigned, name) is 1 in 100,000 ($I_2={{1} \over {100,000}}$) The probability for the combined use is $I_{1 + 2}=I_1 \times I_2={{1} \over {1,000,000}}$)