Very interesting! I'm trying to wrap my head around this. I see a potential security issue with the "refund timeouts". What if Alice post her tx just before the timeout elapses, resulting in Bob never get the chance to receive his BURST? Could you elaborate on that?
Bob's AT must have have less length (expiration) than Alice's AT.So in case Alice sends the TX with the key to Bob's AT just before the expiration, Bob will have time to send the key to Alice's AT afterwards.