Paper 2026/2809

Pastel: Single Secret Leader Election with Private Weights

Abstract

A single secret leader election (SSLE) protocol allows an election of exactly one leader among $n$ parties in a secrecy-preserving manner, where only the elected leader knows it has won until it publicly announces and claims leadership. Motivated by proof-of-stake blockchains where stakes are stored in an encrypted or committed form for the sake of privacy, we design and implement the first SSLE protocol with private weights. Each party's probability of winning an election in our protocol is weighted by stake, and these weights are private. Prior schemes in the literature only allow probabilistic (i.e. expectation of one but can be zero or many leaders) elections in the same setting. Preserving privacy also means public verification is paramount in order for a protocol to be practically reliable. In this respect, our protocol achieves security against malicious adversaries with a concrete implementation. In particular, we concretely implement the needed zero-knowledge proofs and thus do not rely on slashing (financial penalties) to achieve end-to-end malicious security, though slashing can still serve as a performance optimization. Along the way, we observe that previous SSLE protocols in a setting without private weights (either unweighted or with public weights) are either maliciously secure with implementation or post-quantum secure but not both, while our protocol achieves both.