Occult Literature: A First Attempt To Conceal Royal Private Encryption Keys?

I had a theory about spell books and magic squares and other talismans and amulets used by occult practitioners in the past to "cast spells" and "summon demons" in the 15th and 16th centuries by the likes of people such as John Dee. Considering there were court magicians and court astrologers everywhere, what if the true point of a magic square / spell book (not to mention the true role of an astrologer) was most often to conceal an encryption/decryption key for the royal family for them to use for private communications?