Mixed-Weight Committee Selection in Proof-of-Stake: Tunable Stake-Baseline Mixing with Exponential Tail Guarantees and Incentive Compatibility
Proof-of-Stake (PoS) blockchains often select committees in direct proportion to stake, which makes security sensitive to large validators and stake concentration. In such settings, a purely stake-based lottery can sometimes produce committees whose adversarial share crosses the safety threshold, even if the global adversarial stake remains below one third. This paper introduces a simple mixed-weight rule that combines stake with a bounded baseline distribution through a single mixing parameter $\lambda$. The rule leaves committee size, rewards, and VRF-based sortiti