Cribs in the Voynich MS

[Koen G]

I can imaging kind of a continuum of how handy a crib is, depending on a number of factors:

Scenario 1, maximum certainty

You know the underlying language (let's say Latin) and you suspect simple substitution. In this case, even if your crib is a single word, it will be incredibly useful. Say you have a picture of the sign Aries, and with it ciphertext Bsjft. Congratulations, your cipher is now solved.

Scenario 2, uncertain language

This is the same as scenario 1, only now you don't know the underlying language. You can start testing your crib by plugging in "Aries", but also any vernacular versions that seem plausible (Widder, Bélier, Ram...) and spelling variations. As soon as you find something that works, you will also need to test this system with other cribs. As long as you are dealing with simple substitution though, a few words should be enough to get you started.

Scenario 3, uncertain crib

You suspect simple substitution but your crib is a sentence and you don't know the exact phrasing. I think this might be more difficult than scenario 2, because there can be variation in terms of the words selected, syntax, word order and spelling. However, if you do know the underlying language, you should have a decent chance of success even without using computers.

Scenario 4, uncertain cipher

Imagine you know the underlying language and are certain that you are looking for the word "Aries", but the ciphertext is "aarbicedse". In this case, you could still either solve it manually or use a computer to brute-force a solution. Some ciphers will probably be unsolvable this way, though I don't know enough about it to know whether this would be the case for any of the standard medieval ciphers one would encounter.

Scenario 5, combination of uncertainties

All of the above, apart from scenario 1, come with their own set of difficulties. But now imagine you are not certain about the exact wording of your crib, you don't know the underlying language and you don't have a clue about the type of cipher you're dealing with. You don't even know if the meaning of your ciphertext is retrievable (one-way cipher) or if it contained any meaning to begin with. You also don't know if your text describes the drawings in a straighforward way, or in which way it relates to them, if at all. That's the situation we're in.