Paper 2019/1320

Homomorphic Encryption Random Beacon

Alisa Cherniaeva and Ilia Shirobokov and Omer Shlomovits

Abstract

A reliable source of randomness is a critical element in many cryptographic systems. A public randomness beacon is a randomness source generated in a distributed manner that satisfies the following requirements: Liveness, Unpredictability, Unbiasability and Public Verifiability. In this work we introduce HERB: a new randomness beacon protocol based on additively homomorphic encryption. We show that this protocol meets the requirements listed above and additionaly provides Guaranteed Output Delivery. HERB has a modular structure with two replaceable modules: an homomorphic cryptosystem and a consensus algorithm. In our analysis we instantiate HERB using ElGamal encryption and a public blockchain. We implemented a prototype using Cosmos SDK to demonstrate the simplicity and efficiency of our approach. HERB allows splitting all protocol participants into two groups that can relate in any way. This property can be used for building more complex participation and reward systems based on the HERB solution.