1400s amateur crypto and human puzzle tendencies

[byatan]

I understand that during the time period the ms was written, it is well documented that crypto was in common use for general government written communications that might foreseeably be subject to inspection by one's adversaries.

This has the implication that knowledge of the existence and use of crypto, if not of the specific methods themselves, would have been reasonably widespread beyond those who actually used or computed crypto for official purposes. I don't know how well this is documented; namely: how much evidence is there for the use of cryptography outside of government in the early renaissance?

What are some estimates of the contemporary distribution of literacy in terms of profession?

If today's humans are any indication, some of those with writing ability would have had the tendency to create or explore various written puzzles. Crypto is an obvious option here. What kind of written puzzles did the literate engage in?