One of the more interesting aspects of developments in cryptocurrency, web3 and decentralised finance is the issue of fungibility. This is an important property of money, but not of property, if you see what I mean. All money is the same, all property isn’t. This why, as J.P. Koening pointed out, if you are a fan of anonymity and have perfectly good legitimate reasons for keep your transactions away from the prying eyes of your spouse, co-workers, mom or tax authorities then sending your crypostash through a “mixer” virtually guarantees that your perfectly legitimate pile of coins will be commingled with the proceeds of crime. After all, according to Chainalysis around a quarter of all of the funds sent to mixers in 2022 come from “illicit” addresses.
Well, you might think, so what? My Bitcoins are my money. But they are not. Your Bitcoins are your property, and that’s very different.
We’ll come back to that point shortly, but first let us look at mixers in more detail. The Financial Crimes Enforcement Network (FinCEN) has classified mixers are money transmitters under the Bank Secrecy Act (BSA). This. Means that they have an to register with FinCEN and implement anti-money laundering (AML) procedures that are undoubtedly at odds with the goals of most people using mixers. Remember that mixers ability to obfuscate the source of funds depends on volume. If fewer people use the mixer it becomes easier to track funds through the mixing process.
One of the most used mixers is Tornado Cash. This has attracted headlines for being used to launder the proceeds of a number of major cryptocurrency exploits, including a $375m attack on Wormhole in February and a $100m hack of the Horizon Bridge in June. Earlier this year, the CEO Roman Semenov explained that his tool has many important uses. He said that, for example, it is an important mechanism for cryptocurrency traders who want to hide their wealth lest they fall prey to “kidnapping, torture and blackmail.”
Well, that maybe, but a few days ago The Office of Foreign Assets Control (OFAC), the agency tasked with preventing sanctions violations, added Tornado Cash to its running tally of blacklisted people, entities and cryptocurrency addresses. As a result, all U.S. persons and entities are prohibited from interacting with Tornado Cash or any of the Ethereum wallet addresses tied to the protocol. Those who do may face criminal penalties.
This has had knock-on effect
Mixed Up
In the mundane world of dollar, dollar bills we have the concept of “money laundering” to describe what happens when dirty money is mixed with clean money (surely every one of us has touched banknotes that have been involved in some criminal activity!). But this doesn’t work for bitcoins. The “tainted” money stays tainted. Ross Anderson, Ilia Shumailov and Mansoor Ahmed from the Cambridge University Computer Laboratory wrote a terrific paper on this theme a couple of years ago. In “Making Bitcoin Legal” they pose some interesting questions about what to do with tainted cryptocurrency asking, for example, “If an identified customer says ‘Hi, what will you give me for UTXO x?’ and the exchange replies, ‘Sorry, 22% of that was stolen in a robbery last Tuesday, so we’ll only give you 78%’ does the customer then have to turn over the crime proceeds?”. Their idea of a public “taintchain” is an interesting way forward. This would be a mechanism to make stolen coins visible, in which case they might display a futuristic Gresham’s Law dynamic as good coins drive out bad ones!
Whether by taintchain or some other mechanism, it’s actually pretty each to track dirty bitcoins. You can see where this might lead: What if law enforcement agencies go to the biggest miners in the world and tell them that if they continue to confirm easily identifiable mixing transaction outputs, they will be accused of money laundering? This is not difficult to imagine, which suggests to me that Bitcoin’s lack of fungibility has far-reaching implications.
As I have written before, we could well see a strange and interesting twist in the world of cryptocurrency that has no analog in the analogue world of notes and coins: black and white money, or clean and dirty money, or light and dark money (an idea that goes back to the earliest days of cryptocurrency) in which some bitcoins will be worth more than others! Maybe a year or two from now, exchanges will be quoting two BTC-USD pairs: clean BTC at $100,000 and dirty BTC at $75,000. This doesn’t happen for GBP-USD or JPY-GBP, which confirms my feeling that whatever Bitcoin is, it isn’t currency.