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August 11, 2015, 05:38:55 PM |
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so, I bought some bitcoins, send them to Address A. The exchange now knows that address. It's in their books, associated with my identify and fiat-world accounts.
In the humanized blockchain speak (as far as I understand it), this would be
"Address A owns 5 btc"
I'm a business, so I've implemented some payment software that generates new addresses for each of my customers. For whatever reason, I want to keep my business activity private from the exchange - say, for example, they are banning accounts associated with selling frying pans, because the exchanges jurisdiction outlaws selling frying pans. I happen to be selling frying pans.
"Address B owns 1 btc" "Address C owns 1 btc" "Address D owns 1 btc"
I go to make a new transaction. The software scans for outputs that I own
An investigator stumbles across my frying pan webfront and wants to figure out if I'm abiding by the law of his jurisdiction. He buys a frying pan.
"Address E owns 1 btc"
The investigator now knows address E is the one selling frying pans.
If I then go to make a transaction, say, for 8.5, all of those outputs would be used in a new transaction. All of those outputs would be used, and the change would go back to a new address, which we'll call address F.
So now address A, which has identifying information tied to it via the exchange, is now tied to address F, which is the change from my transaction, and they're all tied to my frying pan business.
And if you say "well, we could just modify it so that when you craft a transaction, you can select outputs for your inputs", well then you've destroyed fungibility. And if you say "well, you could just use a separate private key for your frying pan business", again, is it fungible?
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