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election.go - Leader Election through Sortition in Canopy Blockchain

This file implements the election sortition mechanism for the Canopy blockchain's Byzantine Fault Tolerance (BFT) consensus protocol. It provides a fair, secure, and decentralized way to select block proposers (leaders) based on their stake in the network.

Overview

Election sortition in Canopy is designed to:

  • Select block proposers (leaders) in a verifiable random manner
  • Weight selection probability based on validator stake
  • Prevent various attacks on the consensus mechanism
  • Ensure fair participation in the consensus process
  • Provide fallback mechanisms when needed

Core Components

Election Sortition Process

The election sortition process uses a multi-step approach to select leaders:

  1. Verifiable Random Function (VRF): Each validator generates a provably random value using their private key and common seed data. This creates unpredictability while allowing verification.

  2. Stake-Weighted Threshold: Validators with more stake have a higher probability of becoming candidates. The system calculates a threshold based on each validator's voting power relative to the total.

  3. Candidate Selection: Validators whose VRF output falls below their threshold become candidates for leadership.

  4. Leader Selection: From all valid candidates, the one with the lowest VRF output becomes the leader for the current round.

  5. Fallback Mechanism: If no candidates emerge, the system falls back to a stake-weighted pseudorandom selection.

Sortition Parameters

The system uses several parameters to control the sortition process:

  • Expected Candidates: The system targets having approximately 10% of validators as candidates, with minimum and maximum bounds.
  • Voting Power: A validator's stake or voting power influences their probability of becoming a candidate.
  • Seed Data: Includes previous proposer addresses, block heights, and round numbers to prevent manipulation.

Verification System

The sortition process includes robust verification mechanisms:

  • VRF Verification: Anyone can verify that a validator's random value was correctly generated without knowing their private key.
  • Candidate Verification: The system can verify if a validator is legitimately a candidate based on their VRF output and stake.
  • Leader Selection Verification: The process of selecting the leader from candidates is deterministic and verifiable by all participants.

Security Features

The election sortition mechanism includes several security features:

  • Protection Against Grinding Attacks: By including previous proposer addresses in the seed data, validators cannot manipulate the process by repeatedly trying different inputs.

  • Protection Against DDoS Attacks: The identity of the leader isn't known until the process begins, making it difficult for attackers to target specific validators in advance.

  • Stake-Weighted Fairness: The probability of becoming a leader is proportional to a validator's stake, ensuring economic alignment with network security.

  • Non-Malleability: The use of BLS signatures provides non-malleability and uniqueness, making them suitable for the VRF implementation.

  • Deterministic Leader Selection: Once candidates are identified, the selection of the leader is deterministic, preventing manipulation of the final selection.