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Digital Finance Seminar Series: Joachim Neu, a16z
by
Fri, Oct 24, 2025
1:30 PM – 3 PM EDT (GMT-4)
750 Schapiro CEPSR
530 W 120th St, Room 750, New York, NY 10027, United States
36
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Details
Registration is recommended but not required for CUID holders. Columbia-affiliated walk-ins will be accepted at the door.
"Accountable Liveness"
The two classical security properties of blockchain consensus protocols are safety (confirmed transactions are consistent) and liveness (transactions do get confirmed). Recent works have strengthened safety with accountability: if safety breaks, then "many" adversary nodes can be proven to be protocol violators. In this talk, we explore if and how accountability can be achieved for liveness ("if liveness breaks, then 'many' adversary nodes can be proven to be protocol violators"). We prove that accountable liveness is achievable if and only if more nodes are honest than adversarial, and "the network is more synchronous than asynchronous" (made precise in the talk). What is more, our protocol identifies a near-optimal number of adversarial nodes. Our results provide rigorous foundations for liveness-accountability heuristics such as the "inactivity leaks" employed in Ethereum. Paper: https://eprint.iacr.org/2025/693
"Accountable Liveness"
The two classical security properties of blockchain consensus protocols are safety (confirmed transactions are consistent) and liveness (transactions do get confirmed). Recent works have strengthened safety with accountability: if safety breaks, then "many" adversary nodes can be proven to be protocol violators. In this talk, we explore if and how accountability can be achieved for liveness ("if liveness breaks, then 'many' adversary nodes can be proven to be protocol violators"). We prove that accountable liveness is achievable if and only if more nodes are honest than adversarial, and "the network is more synchronous than asynchronous" (made precise in the talk). What is more, our protocol identifies a near-optimal number of adversarial nodes. Our results provide rigorous foundations for liveness-accountability heuristics such as the "inactivity leaks" employed in Ethereum. Paper: https://eprint.iacr.org/2025/693
Campus Access
In accordance with the University's current visitor guidelines, all non-Columbia guests will receive a QR code within a few hours of the event date. The code will be sent to you via email from CU Guest Access and must be presented for campus entry, along with a government-issued ID. Please note, this is not the same as the Campus Groups event QR code. Accessibility
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Where
750 Schapiro CEPSR
530 W 120th St, Room 750, New York, NY 10027, United States
Speakers
Joachim Neu
a16z
Joachim Neu is a post-doc Research Partner at a16z Crypto Research led by Tim Roughgarden. Previously, Joachim earned a PhD from Stanford, advised by David Tse. His current research focus is blockchain-era consensus and decentralized-systems security. His broader interests include distributed systems security and applied cryptography.