Bitcoin Privacy & Address reuse

[o_e_l_e_o]

I assume this is more than enough, to secure my coins privacy-wise, isn't it?

Yes, that's more than enough, although I shudder a little at the thought of how much you have paid in fees to do all that.

If it was me, I would probably have just left my coins in Sparrow for more free remixes. I imagine it is fairly unusual to take outputs from Whirlpool and immediately feed them in to JoinMarket, so that potentially gives blockchain analysis companies something to latch on to.

[apogio]

Yes, that's more than enough, although I shudder a little at the thought of how much you have paid in fees to do all that.
If it was me, I would probably have just left my coins in Sparrow for more free remixes.

You 're right. Unfortunately I couldn't leave my computer (Sparrow) turned-on since I 'll not be home for a week. I 've lost a total 2.3% of my original satoshi.

I imagine it is fairly unusual to take outputs from Whirlpool and immediately feed them in to JoinMarket, so that potentially gives blockchain analysis companies something to latch on to.

I don't understand this. Could you elaborate please?

[o_e_l_e_o]

I don't understand this. Could you elaborate please?

It is easy to identify coinjoin transactions when examining blockchain data. Coinjoin isn't useful because the transactions are secret - they aren't - but because it is difficult or impossible to know which inputs are linked to which outputs.

However, you need to be aware of how you spend those outputs. If you send outputs from a coinjoin to Binance, for example, then there are probably lots of other people who are also sending their outputs to Binance, so yours will blend in with the crowd. However, I imagine it's fairly unusual to send coinjoin outputs to a different coinjoin implementation. If you are the only user spending your outputs in this way, then a blockchain analysis company might make that connection. If there are 10,000 Whirlpool outputs spent today, and only 5 of them go directly to JoinMarket, then those outputs are potentially linked.

[apogio]

If you are the only user spending your outputs in this way, then a blockchain analysis company might make that connection. If there are 10,000 Whirlpool outputs spent today, and only 5 of them go directly to JoinMarket, then those outputs are potentially linked.

But how can they know that? Considering that I run Jam on my node. I haven't seen the code but is JoinMarket connected to some central servers? If not, how can they know?

[o_e_l_e_o]

If not, how can they know?

By examining the publicly viewable blockchain data. As I said above, coinjoin transactions are easy to identify.

For example, here is a recent JoinMarket coinjoin I just pulled from the blockchain: https://mempool.space/tx/98423f23138446f079442bda7856b87cba075d15142ae756e06dcbdc0eb6b61c
It has all the characteristics of being a JoinMarket coinjoin which makes it easily identifiable - large number of inputs and outputs, similar number of inputs and outputs, all inputs are from segwit addresses, multiple outputs of identical values (0.04416277 BTC in this case) in order to obfuscate which is which, and if you look back in time the majority of the inputs have come from similar JoinMarket coinjoins.

Similarly, here is a recent Whirlpool coinjoin I just pulled: https://mempool.space/tx/5a734035c9745820dc98ab79209a1e44d4fbd2b7a0ed1dd417131be31a7ad763
These are even easier to identify, since Whirlpool uses fixed pool values of 0.001 BTC, 0.01 BTC, 0.05 BTC, or 0.5 BTC, they always have the same number of inputs and outputs, and two inputs will always be slightly more than the pool size in order to pay the transaction fee.

As I said, the privacy gain from coinjoin transactions comes from it being impossible to link the inputs to the outputs, not from the coinjoin transaction itself being hidden or secret. A blockchain analysis company can easily watch where all the outputs of every coinjoin transaction go, but if they don't know who owns those outputs, which other outputs that person controls, or who owns the addresses they are being sent to, then they can't do anything with information. But if a very small number of outputs all go the same unusual and identifiable place, which I imagine would the case when taking outputs from one coinjoin implementation and sending them to a second coinjoin implementation, then they can infer common ownership. (I have no data on this, I am just postulating that moving coins from one coinjoin implementation directly to a different coinjoin implementation is not a very common thing to do.)

[apogio]

If not, how can they know?

By examining the publicly viewable blockchain data. As I said above, coinjoin transactions are easy to identify.

For example, here is a recent JoinMarket coinjoin I just pulled from the blockchain: https://mempool.space/tx/98423f23138446f079442bda7856b87cba075d15142ae756e06dcbdc0eb6b61c
It has all the characteristics of being a JoinMarket coinjoin which makes it easily identifiable - large number of inputs and outputs, similar number of inputs and outputs, all inputs are from segwit addresses, multiple outputs of identical values (0.04416277 BTC in this case) in order to obfuscate which is which, and if you look back in time the majority of the inputs have come from similar JoinMarket coinjoins.

Similarly, here is a recent Whirlpool coinjoin I just pulled: https://mempool.space/tx/5a734035c9745820dc98ab79209a1e44d4fbd2b7a0ed1dd417131be31a7ad763
These are even easier to identify, since Whirlpool uses fixed pool values of 0.001 BTC, 0.01 BTC, 0.05 BTC, or 0.5 BTC, they always have the same number of inputs and outputs, and two inputs will always be slightly more than the pool size in order to pay the transaction fee.

As I said, the privacy gain from coinjoin transactions comes from it being impossible to link the inputs to the outputs, not from the coinjoin transaction itself being hidden or secret. A blockchain analysis company can easily watch where all the outputs of every coinjoin transaction go, but if they don't know who owns those outputs, which other outputs that person controls, or who owns the addresses they are being sent to, then they can't do anything with information. But if a very small number of outputs all go the same unusual and identifiable place, which I imagine would the case when taking outputs from one coinjoin implementation and sending them to a second coinjoin implementation, then they can infer common ownership. (I have no data on this, I am just postulating that moving coins from one coinjoin implementation directly to a different coinjoin implementation is not a very common thing to do.)

I totally understand, but I really assume that they wouldn't bother. The only reason why I did it was because I wanted to experiment with those conjoin apps. I won't repeat it though.

I will keep using Jam however. It seems too easy to me.

[o_e_l_e_o]

I totally understand, but I really assume that they wouldn't bother.

Maybe. Maybe not. We'll never know. Just pointing out that unusual uses cases like this do provide something for analysis companies to latch on to.

I will keep using Jam however. It seems too easy to me.

As I said above I've never used Jam, but I've been using JoinMarket via its own GUI for years and don't have any real complaints.