Fair exchange is one of the most fundamental human-to-human activity in a society. In a simple case, we have two users Alice and Bob, where Alice has a commodity A, and Bob has a commodity B that they want to exchange. While fairness has several definitions, the one we will focus on is: If and only if, Alice gets commodity B, Bob gets commodity A. Assuming a trusted third party solves the exchange, however, it introduces new problems of centralized trust. On the other hand, Cleve’86 showed that the above notion of fairness is impossible in the absence of an honest majority of parties. Many academic works since then have relaxed the notion of fairness using game-theoretic incentives for the involved parties. Recently, with the advent of blockchains, we have solutions that allow a fair exchange between a buyer’s payment and a seller’s digital good. While such an exchange is the fundamental operation for a functioning economy, the current solutions are still lacking due to various issues like poor privacy, efficiency, and limited compatibility.

In this talk, we will see how to overcome these issues and challenges using novel cryptographic tools. Specifically, we will learn about adaptor signatures that allow for an efficient solution for fair payments between a buyer and a seller, with better privacy and compatibility. We will also see how to expand the functionality of adaptor signatures to support more applications of fine-grained information sales.

Aravind in short, is a lecturer at The University of Sydney’s School of Computer Science. His research focuses on cryptography and decentralized systems like Blockchains. He aims at developing provably secure cryptographic tools in combination with game-theoretic techniques to address privacy, fairness, and efficiency issues in decentralized applications. Previously, he was a postdoc at NTT Research and Carnegie Mellon University supervised by Elaine Shi. He finished his Ph.D. at the University of Erlangen Nuremberg, Germany with Dominique Schröder as his advisor in 2021.