reply on: What's the role of transaction size in onchain privacy? \ stacker news ~bitcoin

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142 sats \ 2 replies \ @kruw 8 Feb \ on: What's the role of transaction size in onchain privacy? bitcoin_beginners

If a transaction size is a round number in sats or Dollars, it's probably the payment and the other one the change.

Yes, this is one heuristic for distinguishing the payment output from the change output. Other fingerprints include comparing each output's script type/version/locktime/feerate to the origin inputs once both outputs are eventually spent.

Also mostly small UTXOs are mostly the transaction and the bigger one probably the change.

I think you have this backwards - If many inputs are consolidated in a transaction and two outputs are created, the bigger output is probably the payment.

Am I still anonymous in a coinjoin if I lower the minimum amount from 0.01 BTC (which is a lot imo).

This default minimum of 1 million sats hasn't been changed since the price of BTC was $15k 😅 Since the mempool is empty, you can bypass this warning and coinjoin smaller amounts without wasting too much in fees.

Shouldn't this mean having never used an exchange with a wallet makes onchain Bitcoin way more private than its reputation?

You should always try to avoid KYC of any form for any transaction. However, Bitcoin's reputation for poor on chain privacy is generally accurate: Unless you take specific measures to control how your UTXOs are spent, you will casually link all of your transactions together over time.

Lightning fixes this for high volume. Coinjoin fixes this for high value.

21 sats \ 1 reply \ @kilianbuhn OP 8 Feb

Shouldn't this mean having never used an exchange with a wallet makes onchain Bitcoin way more private than its reputation?

You should always try to avoid KYC of any form for any transaction. However, Bitcoin's reputation for poor on chain privacy is generally accurate. Unless you take specific measures to control how your UTXOs are spent, you will casually link all of your transactions together over time.

But why tho? Never used an exchange with this wallet. Always VPN. Widely used wallet so not that uncommon type/version/locktime/feerate. Most transactions have odd sizes. Now what? Where is the attack surface on that wallet?

100 sats \ 0 replies \ @kruw 8 Feb

But why tho? Never used an exchange with this wallet. Always VPN. Widely used wallet so not that uncommon type/version/locktime/feerate. Most transactions have odd sizes. Now what? Where is the attack surface on that wallet?

Assuming you are also using your full node or client side block filters to protect your privacy during synchronization, then the remaining attack surface would be the common input ownership heuristic.

Widely used wallet so not that uncommon type/version/locktime/feerate. Most transactions have odd sizes.

Just because you are using random fingerprints doesn't guarantee you are fully protected. If the recipient fingerprints themselves, your change output is identified through process of elimination.