Verification Dilemmas, Law, and the Promise of Zero-Knowledge Proofs

Individuals expose personally identifying information to access a website or qualify for a loan, undermining privacy and security. Firms share proprietary information in dealmaking negotiations; if the deal fails, the negotiating partner may use that information to compete. Regulators that comply with public transparency and oversight requirements can risk subjecting algorithmic governance tools to gaming that destroys their efficacy. Litigants might have to reveal trade secrets in court proceedings to prove a claim or defense. Such “verification dilemmas,” or costly choices between opportunities that require the verification of some fact, and risks of exposing sensitive information in order to perform verification, appear across the legal landscape. Yet, existing legal responses to them are imperfect. Legal responses often depend on ex post litigation remedies that are prohibitively expensive for those most in need, or that fail to address abuses of information entirely. Zero-knowledge proofs (ZKPs)—a class of cryptographic protocols that allow one party to verify a fact or characteristic of secret information without revealing the actual secret—can help solve these verification dilemmas. ZKPs have recently demonstrated their mettle, for example, by providing the privacy backbone for the blockchain. Yet they have received scant notice in the legal literature. This Article fills that gap by providing the first deep dive into ZKPs’ broad relevance for law. It explains ZKPs’ conceptual power and technical operation to a legal audience. It then demonstrates how, and that, ZKPs can be applied as a governance tool to transform verification dilemmas in multiple legal contexts. Finally, the Article surfaces, and provides a framework to address, the policy issues implicated by the potential substitution of ZKP governance tools in place of existing law and practice.