de-anonymize tor/bitcoin
Jeffrey,
this stuff is a bit heavy but if you care for it here are a couple of links:
One obvious technique to de-anonymize tor is to control the 'exit nodes', meaning the nodes that connect Tor to the Internet. If you control enough of them you can de-anonymize a lot of it.
A friend of mine (among other people), found ways to de-anonymize a lot of the 'hidden services' (roughly the 'secret' websites inside tor) much more efficiently. I believe Tor fixed those flaws by now, but it's a pretty ingenious attack: http://www.ieee-security.org/TC/SP2013/papers/4977a080.pdf The bottom line there is that with roughly $11k you can realistically de-anonymize any hidden service on tor. You do that by 'pretending' to be one of the servers handing out the addresses of the hidden services
The third option is to just attack the machine(s) of the 'bad guys', this is for instance what the FBI did a while ago against a network of pedophiles:
http://www.reddit.com/r/onions/comments/ljmrta/founder of the freedom hosting arrested held/ This option is targeted but it always works. The trick there was to attack the computer and then have the computer connect to a non-tor website, by doing that they could get the IP address and de-anonymize the user. Of course once you have control over the machine you can do much more than that, but they stuck to that
As for bitcoin itself, I believe I sent you the Bitlodine paper. Another very good one is this: http://cseweb.ucsd.eduhsmeiklejohn/files/imc13.pdf
Now some of these approaches are probabilistic, (3) is not. But I guess my point is: if you really want to figure out what somebody is doing on tor/bitcoin you can do it given enough resources. Not that it matters too much, but well