I agree with Anton, I never thought of it this way either.
I'm not sure how the process would be supposed to go.
Patron has a secret code to encipher secret knowledge, and reveals all to a scriptorium so they can write the book for him? I doubt that.
Or patron has secret knowledge, which he reveals to scriptorium so they can come up with a code to hide it?
Nah that doesn't make sense either.
Better: Owner is a literate and cultured group of people with enough money to purchase (or the opportunity to "borrow") some materials, they come up with secret code to hide knowledge, and DIY it.
I'm not sure how the process would be supposed to go.
Patron has a secret code to encipher secret knowledge, and reveals all to a scriptorium so they can write the book for him? I doubt that.
Or patron has secret knowledge, which he reveals to scriptorium so they can come up with a code to hide it?
Nah that doesn't make sense either.
Better: Owner is a literate and cultured group of people with enough money to purchase (or the opportunity to "borrow") some materials, they come up with secret code to hide knowledge, and DIY it.