Bril is the only compiler IL I know of that is specifically designed for education.
R. Kent Dybvig's compilers course has had approximately 15 "intermediate" representations designed for his course since at least 2004 -- a consequence of teaching the course using the nanopass compiler framework for scheme. You could broadly divide these into "representations that are restrictions of scheme," and "representations that are increasingly-annotated versions of UIL" where UIL is the underlying intermediate representation. As far as I know, UIL was also designed for this course.
I've only ever seen "one-time" in cryptography to refer to One-Time Pads (OTP). They are literally uncrackable (because every possible plaintext could be encoded by every possible ciphertext) but they achieve that by using a shared private key. The cipher becomes attackable if the key is re-used, hence the "one-time."
But that key has to be exchanged somehow, and that exchange can be attacked instead. Key exchange algorithms can't necessarily transfer every possible OTP which means eavesdropping on the exchange would make an OTP attackable. So the best option we know of that doesn't require secret meetings to share OTPs* really is to use RSA encryption. Once we have efficient quantum-resistant schemes, they'll be the best option we know.
* and let's be honest, secret meetings can be eavesdropped on as well.