The disastrous vulnerabilities in smart contracts sharply remind us of our ignorance: we do not know how to write code that is secure in composition with malicious code. Information flow control has long been proposed as a way to achieve compositional security, offering strong guarantees even when combining software from different trust domains. Unfortunately, this appealing story breaks down in the presence of reentrancy attacks. In this talk I will present a highly general definition of reentrancy and reentrancy security that allows software modules like smart contracts to protect their key invariants while retaining the expressive power of safe forms of reentrancy. I will describe how we can combine a type system and run-time mechanism to enforce this new notion of security even in the presence of unknown code.

This work recently received a best paper award at IEEE S&P ‘21. The paper is available at https://ethan.umiacs.io/papers/serif.pdf


Ethan is currently a post-doc at the University of Maryland working primarily with Mike Hicks and is on the market for tenure-track academic jobs this year. His research focuses broadly on designing secure decentralized systems and building tools to ease their development using programming languages and applied cryptography. He completed his PhD at Cornell in August 2021 working with Andrew Myers and Ari Juels, and is a proud alumnus of Brown undergraduate Computer Science program (class of 2012). More information is available at his website: https://ethan.umiacs.io/