Combining UTXOs: Privacy Risks and Wallet Strategies

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#1Oct 10, 2019, 08:22 PM
Changing your address regularly is supposed to enhance privacy, but what if risks are still there even when we do that? I was thinking about this while trying to figure things out today. I drew a little diagram to help myself understand it better.
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matrix2021Full Member
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#2Oct 11, 2019, 12:06 AM
That’s a valid point. Wallets can pick any inputs for transactions. Sure, oldest-first is a method, but there are better options out there, depending on what you’re aiming for, like privacy or fees. Coin selection algorithms are constantly being tweaked.
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Ba5edGuruFull Member
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#3Oct 11, 2019, 05:28 AM
Totally depends on the wallet. If you're using Electrum, there’s a coin control feature. You can pick exactly which input to use. Like, if you have 1 BTC and 0.6 BTC, you can select the 0.6 BTC for the transaction.
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bear100Hero Member
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#4Oct 11, 2019, 07:59 AM
From what I learned on this site, you can’t just spend part of an output. You need to spend the whole output and create a change output for the remainder. FIFO isn’t the way to go here.
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#5Oct 11, 2019, 11:56 AM
Exactly, no special consolidation fee exists, just the transaction fee. That fee covers both the combination of UTXOs and the change output. It’s best to consolidate when fees are low, since they depend on the transaction size.
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0xChadNewbie
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#6Oct 11, 2019, 03:27 PM
Just a note, when you're diving into UTXOs, don't mix in addresses, since they're wallet-specific. The FIFO logic in your article doesn’t apply to wallets I’ve seen. UTXOs can be spent in any order as long as the total value is correct.
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Ba5edGuruFull Member
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#7Oct 12, 2019, 04:00 PM
+1, exactly. It’s about combining inputs efficiently.
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#8Oct 12, 2019, 09:24 PM
So consolidation is just about combining inputs, right? Doing it when fees are low is smart. Otherwise, what’s the point of doing it when fees are high?
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Ba5edGuruFull Member
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#9Oct 13, 2019, 12:01 AM
I couldn't find coin control on Mycelium either. Must be limited or outdated.
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#10Oct 13, 2019, 03:01 AM
For Mycelium, I haven’t seen it either. In Electrum though, you should see an option to manage inputs if you right-click them. But if Mycelium doesn’t have that feature, that’s a bummer.
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