This proposal introduces a self-custodial credit system that sits in front of an existing ecash mint. The users balance is held in a trustless credit contract that can be instantly swapped for ecash tokens offchain at the time of payment. Custodial risk only exists while payments are in flight, which is usually seconds, and only for the amount currently being transacted. The balance is always self-custodial and if the mint disappears or is uncooperative the user can unilaterally exit and reclaim their credits onchain.
The protocol works on Bitcoin today and does not require a soft fork or any new opcodes. Infact it doesn't require any opcodes at all. The protocol is almost entirely off chain, every possible way to execute the trustless credit contract results in a MuSig2 taproot key path spend onchain, no Bitcoin Script required.
