Saturday, 29 December 2018

Splitting and selling coins without associating UTXOs with your identity

It's natural for people who support BCH over BSV post-split to want to sell their BSV coins (or vice versa). One significant problem is privacy concerns. If you had, say, 10 BCH utxos before the split and then use the common ways of splitting, it's very likely that it will become clear that all 10 of those utxos were controlled by the same person. If you then deposit the "other" coins to a KYC exchange, it's even worse because it's now clear precisely who owns the coins you didn't sell.

I do have some split coins, and could easily use those split coins to split the rest of my utxos, but doing so would associate all my utxos with the same dust and so with each other.

This made me think: someone should make a basic trustless service that does things like building splitting txs using some split dust. Since multiple people's utxos will be associated with the same dust the association would be misleading and unreliable. I didn't know of such a service, so I built one. While I was building it, I also added support for pushing txs onto the two networks and coordinating coinjoins. The coinjoin requires manual effort and would take place over days, but coinjoin is (IMO) the best trustless way to preserve privacy on transparent blockchains. I definitely think nicer, more user friendly coinjoin implementations for BCH or BSV will show up at some point, but in the meantime I wanted to provide some option for anonymous people to coordinate some coinjoins.

None of the services ask for anyone's private keys or ask anyone to send me their coins.

I imagine Alice and Bob using the service to split their utxos, then coordinating some coinjoins, and then selling the coins they don't want. Due to the common splitting dust being used by multiple people, and the coinjoins after the split, their remaining utxos on one chain would not be tightly linked to the utxos they sold on the other chain. It wouldn't be clear which unspent utxos belong to Alice, Bob, or someone else who used the service.

Now I'm in unfamiliar territory. I'm not starting a business. I'm not charging for the service. And I only plan to run it for two months. I must remain anonymous, so I can't go around talking about it. But I feel like posting about it myself, or posting an onion link (it's a tor hidden service) will be seen as advertising or "shilling." Well, if anyone does want the link then look at the "crosschain" account on memo.cash. Hopefully saying that is OK.

In addition to being privacy oriented (behind tor, no accounts), the service is nice in that everything you need to do is just using the standard client (.e.g., Bitcoin ABC or Bitcoin SV). You need to be able to run commands like decoderawtransaction and signrawtransaction from the console or command line.

I'd rather someone else post about it than me, of course. But I don't see how that would happen. Feel free to ask questions or give me advice about how to proceed.

TLDR: I made an anonymous service to help people split their coins without tightly linking their utxos on both chains, and now I don't know how anyone will know it exists.

submitted by /u/crosschain75
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source https://www.reddit.com/r/btc/comments/aal5in/splitting_and_selling_coins_without_associating/

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