A few questions/comments:
Why is there a 10 sat fee on each tx? Where does that fee go?
I don’t think this design sufficiently protects against double spends by the “issuer” (the person who actually has the UTXO). Your guarantee tx mechanism only really covers the case where someone tries to double spend part of a UTXO balance (in other words, if the penalty lost is less than the value gained by doing a double spend, its worth it to double spend, and in a world where you’re passing around digital IOUs, it’s easy to make it worth it). Later in the post, you mention that there will be a p2p network to gossip fund transfers and that will prevent an issuer from double spending. The problem there is that network latency is non-zero, large network partitions are both real and common, and nodes can come and go anytime (hardware failure, power failure, network partition healing, just because they feel like it, etc). Different nodes on the network might hear about different, conflicting transactions. Nodes will need a way to all come to consensus on what the right set of “sent notes” is. I think you will end up reinventing a lot of the problems solved by bitcoin.
Why did you pick email as the RPC mechanism to transfer these notes? Email is going to add variable amounts of latency and things like spam filters will cause issues.
Alex
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Alex Schoof