The strongest argument against cryptocurrencies used to be that they had yet to show they were much good for anything. Now the strongest argument against them may be that they have become far too good at one thing: enabling crime.

Not long after the first of the private digital currencies, bitcoin, launched in 2009, crooks recognised its appeal. While law enforcement is proving increasingly adept at tracking bitcoin transactions and at times seizing ill-gotten money, the ability to make digital payments without financial intermediaries has facilitated activities such as the selling of illegal goods and services online and money laundering. In a 2019 paper, researchers Sean Foley, Jonathan Karlsen and Tālis Putniņš estimated that 46% of bitcoin transactions conducted between January 2009 and April 2017 were for illegal activity.