FPLotto: A fair blockchain-based lottery scheme for privacy protection

Aiming at the existence of a trusted third party in the traditional lottery and the privacy leakage of the current blockchain lottery scheme, we propose a fair blockchain-based lottery scheme for privacy protection, called FPLotto. Benefiting from a Lagrange interpolating polynomial over a finite field and a verifiable random function, lottery ticket of all users fairly contributes to the generation of winning numbers which is transparent and verifiable to anyone. The discrete logarithm, the one-way property of hash function and VRF provide security and avoid deliberate control of the lottery draw. Moreover, the mixing protocol based on zero-knowledge proofs hides lottery amount and bonus amount, and cuts off the connection among the lottery buyers and the winners for protecting the privacy of users. The scheme guarantees fairness, verifiability, and privacy without a trusted third party. Additionally, we propose a method of aggregation verification based on PLONK reducing the operating cost of lottery agency and speeding up the draw phase.