1-level
You write on parchment, paper, or some other suitable writing material and imbue it with a potent illusion that lasts for the duration
To you and any characters you designate when you cast the spell, the writing appears normal, written in your style of writing, and conveys whatever meaning you intended when you wrote the text. To all others, the writing appears as if it were written in an unknown script that is unintelligible. Alternatively, you can cause the writing to appear to be an entirely different message, written in a different style.
Should the spell be dispelled, the original script and the illusion both disappear.