The first widely distributed and open source version of this typist timing validation idea I saw (and incorporated into my own software at the time) was released by Michael Crichton as part of a password 2nd-factor checker (1st factor a known phrase or even your name, the 2nd factor being your idiosyncratic typing pattern) in Creative Computing magazine that printed the code.

Original here: https://archive.org/details/sim_creative-computing_1984-06_1...