Two factor verification

[ReneZ]

It is perhaps of interest to note that different applications use different words for largely the same thing: identification, verification, authentication.

None of these apply to the Voynich example in the opening post, I am afraid, because both would have to be independent, apply to the same item, and have a very small probability of giving a 'false positive' (i.e. you think they are the same but they are not).
The "two factor" comes in because the probability of two false positives is the product of each individual false positive.

Ages ago, I (half seriously) applied this to the "identification" of the Voynich MS with a genuine old manuscript, and it was three-factor.
1. It is written on old vellum. Let's assume that there is a 1% chance (factor 0.01) that this was previously unused old parchment used by a modern faker
2. It is described in a letter from 1637. Again we can arbitrarily assume a 1% chance that this is actually another MS
3. It has the genuine name of Tepenec in there. Again. 1% chance that this was added by a modern faker

One can argue about all three numbers. They are arbitrary and cannot be computed in reality.

In any case, this three-factor identification of the Voynich MS with a genuine old MS results in a false positive of 0.000001 (1 in a million).