Bob Miller wrote:
I'm not aware of it being allowed, but then, I'm also not aware of any
FCC rule saying an amateur cannot encrypt a message.

Now you are. 47 CFR 97.113(a)(4)

Hams couldn't use ASCII until relatively recently. FCC declared it a code
and said it was illegal for ham use and maintained that stance for years.

--
Britney Spears' Guide to Semiconductor Physics
http://britneyspears.ac/lasers.htm