Malleability of the blockchain's entropy

Cécile Pierrot (1, 2, 3) , Benjamin Wesolowski (4)

1 CNRS - Centre National de la Recherche Scientifique
2 Direction Générale de l'Armement
3 ALMASTY - ALgorithms for coMmunicAtion SecuriTY
4 EPFL - Ecole Polytechnique Fédérale de Lausanne

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. Entropy from the Bitcoin blockchain in particular has been used in lotteries and has been suggested for a number of other applications ranging from smart contracts to election auditing. In this Arcticle, we analyse this idea and show how an adversary could manipulate these random numbers, even with limited computational power and financial budget.

Mots clés: Random number generation; Blockchain; Random Beacon; Bitcoin; Dyck language

Domaines: Cryptographie et sécurité [cs.CR]

Cécile Pierrot, Benjamin Wesolowski. Malleability of the blockchain's entropy. ArcticCrypt 2016, Jul 2016, Longyearbyen, Norway. ⟨hal-01364045⟩