A common misconception is that bitcoin transactions are anonymous. The truth is, unless you are very careful about covering your tracks, your bitcoin transactions can be connected to you. And the transaction records on bitcoin's public database (the blockchain) can never be changed or deleted, meaning they will forever be searchable by authorities or anyone else. Andy Greenberg of Wired reports that researchers were able to "connect someone's bitcoin payment on a dark web site to that person's public account."
[T]he Qatari researchers first collected dozens of bitcoin addresses used for donations and dealmaking by websites protected by the anonymity software Tor, run by everyone from WikiLeaks to the now-defunct Silk Road. Then they scraped thousands of more widely visible bitcoin addresses from the public accounts of users on Twitter and the popular bitcoin forum Bitcoin Talk.
By merely searching for direct links between those two sets of addresses in the blockchain, they found mor ...