The U.S. Treasury’s recent sanctions of Tornado Cash are opening important new fronts in the ever-evolving arms race between government regulators and the digital innovators trying to build a new world without them. This week: Can an open-source piece of code really be deplatformed? Cryptocurrency, and much of the open internet, is based on the idea that computer code is a shared public resource that can live more or less forever online. Bitcoin, to take the best-known example, is nothing but a bunch of servers running the same protocol and tracking the same list of transactions. Tornado Cash, as most of the crypto world knows by now, is a “mixer,” a piece of software that obscures the origin of cryptocurrency. Worried about its use for money laundering, the Treasury Department has been trying to bar people from using it, including by sanctioning Tornado Cash itself. The issue is that Tornado isn’t a person, a country or a company, the typical subjects of Treasury’s blacklists. As we addressed here in the wake of sanctions, it's a self-executing piece of software, something without an owner, a legal residence or a bank account. It might even enjoy some constitutional protections. Last week, we took a look at the First Amendment questions raised by the Tornado sanctions. This week, we’re seeing those questions start to be put to the test in a way that raises the prospect of a broader controversy over the platforming of controversial code, just as the platforming of controversial social media content has become a hot-button political issue. In response to Treasury’s sanctions, GitHub, a platform for software developers, took down pages that were used to develop the tool. Because of the novelty of applying sanctions to open-source software, it is not clear whether GitHub’s takedown was required by law, but, when in doubt, companies often err on the side of complying with the government’s wishes. While the U.S. now forbids its use, a portion of the Tornado code continues to exist on the decentralized Ethereum blockchain network, from which it would be impractical to remove it. On GitHub, the full code had been available in an accessible form, until it was yanked offline. Except… now it’s not offline. Matthew Green, a computer science professor at Johns Hopkins University, announced this week that he has re-uploaded the source code to GitHub. Green, who studies cryptography and teaches students about Tornado Cash’s privacy features, tells Digital Future Daily that this is the first instance he’s aware of in which notable open-source code has gone offline—and it’s worth worrying about. “The idea that source code disappears from the internet is a really bad thing,” he said. In his view, it's not unlike banning or destroying books: It's an act that diminishes the store of shared human knowledge. Though Green has not yet been embroiled in any legal fights over his republication, he is already being represented by the Electronic Frontier Foundation, a veteran of fights with the government over code and expression, which asserts that Green’s republication does not violate the Treasury Department’s sanctions. The group argues that his posting of software code itself for the purpose of study or improvement amounts to speech. Critics of the sanctions argue that they will lead private companies, eager to avoid irritating the government, to take pre-emptive steps against secrecy tools beyond what the law requires, even when they interfere with legitimate privacy applications or free expression. A spokeswoman for GitHub, Sandra Dieron, did not address questions about whether or not the platform planned to take Green’s post down. In a statement, she said, “We examine government sanctions thoroughly to be certain that users and customers are not impacted beyond what is required by law.” Green is no stranger to controversies over software and government power. In 2013, an administrator at Hopkins, which has close ties to the federal government, asked Green to take down a blog post discussing Edward Snowden’s leak of National Security Agency material, then changed course and apologized after the takedown generated online outrage. As the Biden administration steps up its focus on blockchain, and interest in new cryptographic methods continues to grow, Green predicts that fights over secrecy tools will multiply. “This privacy stuff,” he said, “is going to snowball.” | 
