CWI Cryptology Group

Abstract: Trustworthy generation of public random numbers is necessary for the security of many cryptographic applications. It was suggested to use the inherent unpredictability of blockchains as a source of public randomness, for lotteries, smart contracts or election auditing. We analyse this idea and show how an adversary could manipulate these random numbers, even with limited computational power and financial budget. We discuss other solutions to securely generate public randomness, and how to integrate external sources into Bitcoin.