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Comment by alasdair_ | Hacker News Reader

>I have never understood the appeal of BitCoin as a means of purchasing or selling illegal materials. The entire transaction history is literally encoded in a public ledger!

Don't most illegal users use tumblers that commingle money from many addresses and then send back (in different quantities and at random times and sometimes from unrelated addresses) bitcoin of roughly the same value? Or is that no longer the case now that transaction costs are higher?

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It seems like a huge part of criminal investigation is tracing opportunity and motive, and only then proving that the suspect was involved. We conflate filtering with proving all the time. Filtering strategies don't have to hold up in court. They don't have to prove anything, except whether I'm definitely looking at the wrong guy(s). The evidence gathered after I've filtered down to 5 supects is the stuff I'd be using in court. I (proverbial "I", as I'm not in law enforcement) need Due Process for every step after that.

If you can narrow a suspect pool from millions down to hundreds by showing they were at the same 'location' as the perpetrator, that's not great but it's surely a start.

What percentage of people using tumblers aren't up to something sketchy? Even if that's 95% that's still greatly amplifying the signal when you're talking about looking for one individual among a hundred thousand.

That's the scary thing. Today, it's using a tumbler that filter you in. Tomorrow it's not having a 24/7 camera/mic in your house connected to the internet with weakened or no encryption.

Tumblers aren't magic and they're a great example of why you have to look at the security of an entire system with a particular threat model in mind: when law enforcement sees one in use, they don't say it's impossible and give up. Instead, every point where real money enters or leaves the system is an area to apply existing legal tools to compel people to document that they aren't violating money laundering laws, etc. Because every Bitcoin transaction is public that provides a strong disincentive for anyone legitimate to use a tumbler — how many reasons do you have which are strong enough to risk having to prove that you weren't part of another user's illegal activity? — further increasing the likelihood that simply sending or receiving funds from one would be considered probable cause.

I’d assume a lot of mixers are operated or taken over by law enforcement.

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