Private Attacks in Longest Chain Proof-of-stake Protocols with Single Secret Leader Elections

TL;DR

This paper compares the security of proof-of-stake protocols using Single Secret Leader Elections (SSLE) versus Probabilistic Leader Elections (PLE), showing SSLE significantly improves resistance to private and grinding attacks, reducing settlement times.

Contribution

It provides the first quantitative analysis of security improvements in PoS protocols using SSLE over PLE against private and grinding attacks.

Findings

SSLE reduces settlement time by ~25% against 25-33% adversaries.

Security threshold against grinding attacks increases from 0.26 to 0.36 with SSLE.

Settlement time decreases by ~70% for a 20% adversary in SSLE protocols.

Abstract

Single Secret Leader Elections have recently been proposed as an improved leader election mechanism for proof-of-stake (PoS) blockchains. However, the security gain they provide has not been quantified. In this work, we present a comparison of PoS longest-chain protocols that are based on Single Secret Leader Elections (SSLE) - that elect exactly one leader per round - versus those based on Probabilistic Leader Elections (PLE) - where one leader is elected on expectation. Our analysis shows that when considering the private attack - the worst attack on longest-chain protocols - the security gained from using SSLE is substantial: the settlement time is decreased by roughly 25% for a 33% or 25% adversary. Furthermore, when considering grinding attacks, we find that the security threshold is increased by 10% (from 0.26 in the PLE case to 0.36 inthe SSLE case) and the settlement time is decreased by roughly 70% for a 20% adversary in the SSLE case.