Among strategies to deal with toxic change in coinjoins, inclusion is one of them.
Wasabi 1.0 and JoinMarket include toxic change in coinjoins. What does this mean for users and their privacy? Let’s dive in:
Wasabi 1.0 requires around 0.1 BTC to participate in coinjoins, while many different amounts are available on JoinMarket. In JoinMarket, you have to find or become a maker who provides liquidity & decides the values for a coinjoin.
This creates toxic change as takers will likely have input amounts that differ.
With Wasabi 1.0, toxic change is also present in the coinjoin transaction, making it sometimes possible for an outside observer to link the change output to the input. If a user has one 0.17 BTC coin, they can participate in a coinjoin round to get a ~0.1 BTC private coin and a ~0.07 BTC change output.
Is the 0.07 BTC change toxic!? Let’s see…
Even if the coinjoin participant did not intend to make the ~0.07 BTC change output private, there is an opportunity for the change output to inherit some privacy due to the presence of inputs from other users in the same round. For example, if another user in the round had registered both a 0.08 BTC coin and 0.09 BTC coin, they also get a ~0.1 BTC private coin and a ~0.07 BTC change output. The larger the coinjoin, the more difficult it becomes to link a change output to an input.
In the Wasabi 1.0 interface, private coins are labeled with a green shield, while the non-private change coins have a clearly-visible red shield. If a user tries to consolidate by spending them together, they will see a warning discouraging the consolidation.
In many cases, it is still possible to link a change output in Wasabi 1.0 and in JoinMarket to other inputs, which makes the change inclusion strategy in these coinjoins not as robust over time. Pushing this burden on the user is not optimal. What are the other options?
In the next post, we will explore the other strategies to deal with toxic change in coinjoins, namely change isolation and elimination. Follow the full discussion in the Bitcoin Magazine article here: https://bitcoinmagazine.com/technical/toxic-change-wabisabi-bitcoin-coinjoin-privacy
wasabiwallet / Wasabi Wallet
npub167…8schc
2023-03-30 16:15:01
Author Public Key
npub167hmfzj38hkumks4wxny89797la0sf7wnwfrw4enlmcl82msp0cs78schcSeen on
wss://nos.lolPublished at
2023-03-30 16:15:01Event JSON
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"tags": [],
"content": "Among strategies to deal with toxic change in coinjoins, inclusion is one of them.\n\nWasabi 1.0 and JoinMarket include toxic change in coinjoins. What does this mean for users and their privacy? Let’s dive in:\n\nWasabi 1.0 requires around 0.1 BTC to participate in coinjoins, while many different amounts are available on JoinMarket. In JoinMarket, you have to find or become a maker who provides liquidity \u0026 decides the values for a coinjoin.\n\nThis creates toxic change as takers will likely have input amounts that differ.\n\nWith Wasabi 1.0, toxic change is also present in the coinjoin transaction, making it sometimes possible for an outside observer to link the change output to the input. If a user has one 0.17 BTC coin, they can participate in a coinjoin round to get a ~0.1 BTC private coin and a ~0.07 BTC change output. \n\nIs the 0.07 BTC change toxic!? Let’s see…\n\nEven if the coinjoin participant did not intend to make the ~0.07 BTC change output private, there is an opportunity for the change output to inherit some privacy due to the presence of inputs from other users in the same round. For example, if another user in the round had registered both a 0.08 BTC coin and 0.09 BTC coin, they also get a ~0.1 BTC private coin and a ~0.07 BTC change output. The larger the coinjoin, the more difficult it becomes to link a change output to an input.\n\nIn the Wasabi 1.0 interface, private coins are labeled with a green shield, while the non-private change coins have a clearly-visible red shield. If a user tries to consolidate by spending them together, they will see a warning discouraging the consolidation.\n\nIn many cases, it is still possible to link a change output in Wasabi 1.0 and in JoinMarket to other inputs, which makes the change inclusion strategy in these coinjoins not as robust over time. Pushing this burden on the user is not optimal. What are the other options? \n\nIn the next post, we will explore the other strategies to deal with toxic change in coinjoins, namely change isolation and elimination. Follow the full discussion in the Bitcoin Magazine article here: https://bitcoinmagazine.com/technical/toxic-change-wabisabi-bitcoin-coinjoin-privacy",
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