Designing Proof of Human-work Puzzles for Cryptocurrency and Beyond

We introduce the novel notion of a Proof of Human-work (PoH) and present the first distributed consensus protocol from hard Artificial Intelligence problems. As the name suggests, a PoH is a proof that a human invested a moderate amount of effort to solve some challenge. A PoH puzzle should be moderately hard for a human to solve. However, a PoH puzzle must be hard for a computer to solve, including the computer that generated the puzzle, without sufficient assistance from a human. By contrast, CAPTCHAs are only difficult for other computers to solve — not for the computer that generated the puzzle. We also require that a PoH be publicly verifiable by a computer without any human assistance and without ever interacting with the agent who generated the proof of human-work. We show how to construct PoH puzzles from indistinguishability obfuscation and from CAPTCHAs. We motivate our ideas with two applications: HumanCoin and passwords. We use PoH puzzles to construct HumanCoin, th...

• Type: Journal
• Year: 2016
• Where: IACR
• Authors: Jeremiah Blocki, Hong-Sheng Zhou
• Keywords: Biometrics, IACR 2016