KeyPack grin-wallet enhancement, please take a look

[Anynomous]

For convenience, a link to the original 1-of-2 output proposal by David B to eliminate the finalize step.

Eliminating finalize step

Currently, grin transactions are created using the following 3 (simplified) steps: Send - Sender commits to amount, fee, and a public nonce, public excess. It could also commit to tx offset, inputs, change output, and probably others. Receive - The receiver adds their output & rangeproof, and commits to their public nonce and excess. It then updates the total kernel commitment, and signs for their half of the kernel. Finalize - The sender adds their half of the signature, aggregates the 2 part…

It is stated in this new KeyPack proposal that there are

Strong payment proofs

That is something that David had not solved in his proposal. Whats new in this proposal to my understanding is the use of a

1. A time-lock
2. Claimed strong payment proofs.
3. Use of cut-through to eliminate a temporary output (nifty, I also used this in my fun but poor transaction buddy proposal)

The payment proofs is something to really pay attention to, also if the proof works to avoid dispute in case a transaction expires (can the sender not falsely claim the funds were send)? I really wonder how the peoof can work, is the proof included in the transaction output that is dropped “C(r_t, v)”, or no probabbly the kernel.

Another part I do not understand is the “Single fee payment for entire operation”. Even if cut-through is used the transaction does create two kernels, and to my understanding the fees for the eliminated temporary output would still have to be paid for for the first kernel to be valid.