Rethinking Cryptography and Blockchain Attacker Models

Sep 16, 2026

Episode #921

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Abstract

In the past few years, blockchains have emerged as a new class of decentralized systems with wide-ranging applications. But the promise of blockchains has been marred by hype, speculation, and a plethora of high-profile attacks.

The purpose of this talk is to demonstrate, through examples from my research, why blockchain security is challenging. Blockchains operate in a radically new, highly adversarial environment where subtle protocol flaws can be immediately monetized by anonymous actors. This fundamentally intertwines an assortment of fields---cryptography, distributed systems, and mechanism design, among many others. Blockchain security should no longer be thought of from a single lens.

In this talk, I will show powerful new attacks, motivated by blockchains, that erode security through the very same tools typically used to build secure protocols. These attacks provide valuable insights on existing, well-studied security and cryptographic models. In turn, this shows why understanding blockchain security has broader utility and how it can serve as a guiding principle when designing secure systems.

The first part of my talk challenges assumptions in cryptographic models of knowledge by showing powerful bribery attacks in bribery-resistant voting---fixing these attacks requires a stronger notion of knowledge. The second part will discuss new techniques for collusion using blockchains, and how it impacts incentives and models in accountable cryptography.