I suspect that in the future, people who believe that this is a guaranteed way to hide the source of their bitcoins are going to be rather surprised at the capabilities of forensic accounting and a lot of computing power.
I deposit BTC and Buy AUR go to another exchange sell AUR for BTC and withdraw to a fresh new wallet.dat made on another pc with another IP and put it on paper wallet .... how they can find out?
IANAFA (I am not a forensic accountant), so I'm no expert in the matter.
One possibility that comes to mind is that they know the total AUR that the deposited BTC can purchase. They see the depoist from you at the first exchange. Then they find a transaction (or set of transactions) withdrawing the right amount of AUR from the first exchange. They follow these transactions through the AUR blockchain until they see them all deposited into the exact same account at the second exchange. They know the total BTC that the deposited AUR can purchase, so they find a transaction (or set of transactions) withdrawing the right amount of BTC from the second exchange.
In addition they track the source of where you get the initial BTC from, and they track the location that the final BTC are stored or spent. A subpoena and a search warrant, and they confirm that the bitcoins are yours.
I have to develop a way to make it secure, maybe building some shady websites where you purchase things that are not shippable and from that websites to deposit the money in different exchanges and withdraw in also more wallets the final amount, if they still can find it at least they will work their asses off!