Surely this defeats the point of a mixer if you're just running CoinJoin with yourself?
It's pointless as long as third parties know that all of the CoinJoin's inputs are yours.
This is my point in the example above, without other participants nothing is obfuscated, even if old coins are made into new coins.
I get that the coins would still technically be new, but it doesn't do anything to break the connection between old and new coins if you're only mixing coins from the same origin...
The same origin needs to be proved it's the same. A bitcoin transaction can be consisted of inputs that are not owned from the same person.
That I get. The only thing I see happening with the 2014 mix of Crypsy is the following:
Mixing wallets CrypsyA + CrypsyB + CrypsyC etc = CrypsyABCX. There is no UnknownA, B or C to adequately break the connection between stolen and non-stolen coins.
For sure it obfuscated whether the new coins were part of Cryptsy wallet A, B or C. This I don't deny. But mixing stolen coins together only results in stolen coins.
I had thought the point of a mixer was to mix your coins with other peoples, not just your own. Surely this defeats the point of a mixer if you're just running CoinJoin with yourself?
It's not a coinjoin. You get different coins than the ones you started with.
Ok, well whatever software/protocol was used, the hacker simply got back what they put in, as was responsible for all the inputs (-1) - hence got all the outputs (-1).
it doesn't do anything to break the connection between old and new coins if you're only mixing coins from the same origin...
Think of it this way: Alice gets Bob's coins, without knowing who Bob is, and without knowing how Bob got his coins. Alice's old coins are now owned by the mixer, and Alice's old coins can't be linked to Alice's new coins.
The coins are totally different.
This is assuming it was an online mixer that was used, and that the website had 11K BTC liquidity ($5 million back then)? To me they look like simple transactions that consolidates funds.
I do see the logic of the coins not being the stolen ones however, but simply owned by the thief after blatant online mixing. Similar to how any tx makes an old coin new again, as the trail shows. This means the blacklisting could be not for stolen coins, if indeed they were able to mix it with a website (swap them as you put it), but attempting to block profiting from a theft on a somewhat permanent basis.
I'm also guessing that back in 2014 there weren't delays in receiving your coins from online mixers, at least not the one that was potentially used, hence didn't obfuscate anything either...