Author: Bastien TEINTURIER 2021-12-07 13:11:00
Published on: 2021-12-07T13:11:00+00:00
In a discussion between t-bast and ZmnSCPxj, it was agreed that PTLC adaptor signatures should be included in the `commitment_signed` message rather than `update_add_ptlc`. However, it was noted that whenever the commitment changes, peers need to create new signatures and adaptor signatures for all pending PTLCs. This includes new pre-signed transactions that spend a PTLC from the remote commitment, which may require an additional round-trip. In a simple example where one pending PTLC exists in each direction, the party making unrelated updates cannot immediately send their `commitment_signed` to the other party, as this would invalidate their ability to claim the PTLC from the other party's new commitment. Instead, the other party must first send a new message (`remote_ptlcs_signed`) containing their adaptor signatures for the PTLC-remote-success transactions that would spend their future commitment. Only then can the first party safely send their `commitment_signed`. This adds one message in each direction but doesn't add more data to existing messages. ZmnSCPxj also noted that fast-forwards could avoid this issue by delaying the change of the commitment tx. Overall, this protocol change simplifies the process and improves efficiency.
Updated on: 2023-06-03T06:44:04.677913+00:00