The Laboratorium (3d ser.)

A blog by James Grimmelmann

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Content Moderation on End-to-End Encrypted Systems

I have a new draft article with Charles Duan, Content Moderation on End-to-End Encrypted Systems. A group of us received an NSF grant to study techniques for preventing abuse in encrypted messaging systems without compromising their privacy guarantees. Charles and I have been looking how these techniques interact with communications privacy laws, which were written decades ago, long before some of the cryptographic tools had been invented.

This paper has been a lot of fun to work on. Charles and I are birds of a feather; we enjoy spending time at the intersection of law and computer science. Although the details of the analysis are highly technical (in both legal and technological senses), working through them led us to some interesting observations about end-to-end encryption and the structure of the federal communications privacy laws.

Here is the abstract:

End-to-end encrypted online platforms are increasingly common in the digital ecosystem, found both in dedicated apps like Signal and widely adopted platforms like Android Messages. Though such encryption protects privacy and advances human rights, the law enforcement community and others have raised criticisms that end-to-end encryption shields bad behavior, preventing the platforms or government authorities from intercepting and responding to criminal activity, child exploitation, malware scams, and disinformation campaigns. At a time when major Internet platforms are under scrutiny for content moderation practices, the question of whether end-to-end encryption interferes with effective content moderation is of serious concern.

Computer science researchers have responded to this challenge with a suite of technologies that enable content moderation on end-to-end encrypted platforms. Are these new technologies legal? This Article analyzes these new technologies in light of several major federal communication privacy regimes: the Wiretap Act, the Stored Communications Act, and the Communications Assistance for Law Enforcement Act.

While generally we find that these content moderation technologies would pass muster under these statutes, the answers are not as clear-cut as one might hope. The advanced cryptographic techniques that these new content moderation strategies employ raise multiple unsettled questions of law under the communication privacy regimes considered. This legal uncertainty arises not because of the ambiguous ethical nature of the technologies themselves, but because the decades-old statutes failed to accommodate, or indeed contemplate, the innovations in cryptography that enable content moderation to coexist with encryption. To the extent that platforms are limited in their ability to moderate end-to-end encrypted content, then, those limits may arise not from the technology but from the law.

Comments welcome!