[ChuckMcM]

This interpretation is entirely possible, however there are two issues I have with that.

The first is that even in medieval times parchment wasn't cheap. It wasn't like anyone could get there hands on enough to make 200 pages of gibberish unless they were a relatively wealthy doodler.

The second is that were it in code, the sophistication of ciphers in the 1500's was hot high, and generally quite susceptible to the sort of forensic analysis that is covered in the ISI paper linked in the comments. As far as I am aware, the only cipher system, known at that time, that would not succumb would be a one time pad. And in the case of an OTP cipher it would reveal itself in other ways (lots of entropy in the words).

If it isn't clear, I do agree that it 'being in code' is the most likely reason it has not been deciphered, but that the cipher of that time is not breakable given what we know of 'plain text' of those times (the various languages it could have been written in) makes me wonder how we would fare against an alien communication (should we ever pick one up).

[kragen]

> The first is that even in medieval times parchment wasn't cheap. It wasn't like anyone could get there hands on enough to make 200 pages of gibberish unless they were a relatively wealthy doodler.

But consider: > The first person said to have owned the manuscript was the Holy Roman Emperor Rudolf II, who reportedly was intrigued enough to buy it from its previous owner for six hundred ducats, around ninety thousand dollars in today’s money. (According to the manuscript’s radiocarbon dating, the book was already nearly two centuries old at the time of his purchase.)

Supposing it's random — perhaps the person who made it originally, two hundred years earlier, hoped to charge a similar price from either a gullible patron like Rudolf, or someone who hoped to find a greater fool like Rudolf?

[ChuckMcM]

That is a very good point, if the author knew that there was a demand for mysterious documents they may have created one to fill that demand.

[codezero]

Tis is very likely. I bought a map of the US for my dad (he collects old maps) which depicts California as an island some 10-15 years after they were sure it wasn't an island. It turns out that novelty maps were more in demand than real maps.

[codezero]

I just think its unlikely that an alien message would be coded. Our own messages sent with intent to space are not just unenciphered, they include a lot of meta data to make finding the patterns required to understand it easier.

If instead we used a one time pad, we wouldn't have much luck reaching out to aliens. This points to the more likely scenario that the manuscript isn't encoded at all (gibberish) or it was meant to be understood by only one person.