Donating to a miner's address, what kind of "change" would I expect?

[OROBTC]

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Most miners have a (relatively anyway) fixed address.  Here is one from Poolin that was the last block winner as I write:

191sNkKTG8pzUsNgZYKo7DH2odg39XDAGo

There is a substantial balance of BTC there (over 400 BTC now).


What happens to the "change" if someone were to donate, say, BTC0.0001 (+ small fee) to Poolin's address?  Would that BTC received back as change then be considered "clean"?

Asking for a friend...

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[ranochigo]

No. There is no difference between a change of that transaction and of a regular transaction. Both of them will be linked or tainted to the inputs used in that transaction. Taint is mostly determined by linking the UTXO through the chain of transaction. Since your change is still linked to your inputs, there will be no difference no matter who you send your Bitcoins too.

The only way to reduce the taint is to say, if you send Bitcoins to a miner and the miner sends one of their UTXO from the block rewards to you in a separate transaction. The coins that you receive would be considered clean.

[pooya87]

No. It doesn't matter what the destination is, the change output is still linked to the same input.

input ┌───── donation address
      └───── change address

The only coins that can be considered "clean" (relatively) are the coinbase reward sometimes it is also known as "virgin coins". I wouldn't even call the fees added to that reward "clean" specially in cases where the fee is intentionally too large.

[Quickseller]

If you were to send 0.0001BTC to poolin's address, it would be obvious to most that you are sending a small amount to poolin, and that the change address belongs to you.

If however, you were to send 0.0001BTC to a never-before-used address, and had change sent to a never-before-used change address, there might be some techniques a blockchain analysis company could determine which is the change address, depending on how the outputs are eventually spent, but it would not be obvious which is the change address. If you send BTC to yourself via two outputs, some blockchain analysis companies may be able to conclude you just sent BTC to yourself via two outputs, depending on how the outputs are eventually spent, and how the change outputs from subsequent transactions are eventually spent.

[Charles-Tim]

The only coins that can be considered "clean" (relatively) are the coinbase reward sometimes it is also known as "virgin coins". I wouldn't even call the fees added to that reward "clean" specially in cases where the fee is intentionally too large.

But i think there should be differences between virgin Bitcoin (which is the block reward mined by miners) and clean bitcoin (which are Bitcoin that can not be linked back to the previous transactions). In my opinion, clean bitcoin are coins that can not be linked back to the original addresses. Like the one exchanged for monero and back into bitcoin in an absolute decentralized exchange, or the a mixing service provided by well rightly functioning mixers. Also Bitcoin transactions on CoinJoin wallets like Wasabi could be regarded as clean bitcoin as the transaction impossible to be tracked.

[ranochigo]

But i think there should be differences between virgin Bitcoin (which is the block reward mined by miners) and clean bitcoin (which are Bitcoin that can not be linked back to the previous transactions). In my opinion, clean bitcoin are coins that can not be linked back to the original addresses. Like the one exchanged for monero and back into bitcoin in an absolute decentralized exchange, or the a mixing service provided by well rightly functioning mixers. Also Bitcoin transactions on CoinJoin wallets like Wasabi could be regarded as clean bitcoin as the transaction impossible to be tracked.

That is not the definition of clean coins. Clean coins or otherwise known as untainted coins are those which were never associated with any illicit activities via transaction linkage or has went to specific addresses. The level of taint on a specific UTXO doesn't necessarily concern the user's privacy nor is that of any concerns here. CoinJoins are the opposite of taint; due to the nature of the transactions, you're more likely to have tainted coins after using CoinJoin.

Coins directly from the block rewards are clean as they've never been associated with anything else. I wouldn't be surprised if some miners starts to use the fees as a way to clean their Bitcoin but taint is really not that much of a concern.

[Charles-Tim]

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You are right, I even create a thread recently on bitcoin discussion board, the thread is about MARA mining pool and there was a quote:

“By excluding transactions between nefarious actors, we can provide investors and regulators with the peace of mind that the bitcoin we produce is ‘clean’, ethical and compliant with regulatory standards,” Marathon said in a statement.

So theoretically this type of coins should be called clean bitcoin including the ones mined by miners as block reward. I am not implying MARA are confirming clean bitcoin transactions because their statement is not even entirely true for now, but just an illustration.