Does OTR encrypt everything but the first message?

Question

Information Security

Hey!
A bird sang to me here that libotr encrypts everything except the first message. Is it true?
Tell me more about it. How does Off the record encryption work in general, what strength, what algorithm (AES?), what attacks?

Answer 1

With questions like these, the following comes to mind:

“On two occasions I have been asked, 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' […] I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.”
—Charles Babbage, Passages from the Life of a Philosopher
(1864)