Comment by fbdab103

Even if there was ambiguity, some data is better than none. Given enough training data, I suspect you could find repeatable patterns in standard typists: on a qwerty layout, after typing an "A", "Q" takes 1.2-2.3x as long to type as a "J" kind of pairwise tempo patterns. Anything to reduce the search space from brute-forcing every candidate character.

Even better if the target uses a passphrase, "hXXXse battXXX stXXXXX cXXXXXX" becomes interpretable given a few landmark letter identified with high probability.