selected_utxos.md

UTXOs

Given that:

• ETH is a token user wants to send
• OMG is a fee token

ETH	OMG
5	5
10	10
15	-
20	-

Strategy

Pick fee tokens first for the stealth inputs (because fee token is often used)

Send Amount (ETH)	Fee Amount (OMG)	Inputs	Stealth Inputs
5	3	5 ETH, 10 OMG	5 OMG, 20 ETH
35	8	20 ETH, 15 ETH, 10 OMG	5 OMG
35	15	20 ETH, 15 ETH, 10 OMG, 5 OMG	-
12	15	20 ETH, 10 OMG, 5 OMG	15 ETH
30	10	20 ETH, 15 ETH, 10 OMG	5 OMG
15	10	15 ETH, 10 OMG	5 OMG, 20 ETH

Example 1. Makes sense.
Example 2. Makes sense
Example 3. Makes sense
Example 4. Makes sense

Example 5. This would have no benefit because you will return an output of 5 OMG, which is equivalent to the input you put in. What you could do here is put an extra ETH input.
Example 6. Again, this would have no benefit as you would return the same stealth inputs as outputs. What you could do is add two inputs of the same currency.

I have clarified the logic in what I wrote:

U < 3; input amounts match corresponding currency payables exactly -> Stealth merge if 2 or more UTXOs of the same currency available.
U < 4; input amounts exceed corresponding currency payables -> Stealth merge if 1 or more UTXOs available on a currency where we expect "change"

Thanks! The above would serve as good test cases!

We also need to clarify two things:

• Do we prioritise larger or smaller inputs for stealth merge? 🤔
• How do we prioritise currencies for stealth merge? I propose we order currencies by number of UTXOs, given that each currency has an exit queue and this is what we are trying to shorten in the case of a mass exit.