Sounds like they are trying to achieve perfect forward secrecy per message. Typically you might do this with Diffie-Hellman using ephemeral derivation pairs per

Sounds like they are trying to achieve perfect forward secrecy per message. Typically you might do this with Diffie-Hellman using ephemeral derivation pairs per session. This is good practice as if any one session key is broken, that has no effect on the privacy of past or future messages encrypted under different session keys. They seem to be claiming to use their own crypto based on the parent comment (red flag) and no signature scheme over the top of it to prove a consistent identity, so I'm not sure what they would be doing. Establishing encrypted pipes over an observable medium is very doable, but providing a way to trust that the party on the other end of the pipe is who you think it is is the hard part as you pointed out.