Proof of Contribution (PoC) Consensus

QFC uses a novel consensus mechanism called Proof of Contribution (PoC) that rewards validators based on their multi-dimensional contributions to the network.

Overview

Unlike traditional Proof of Stake (PoS) which primarily considers staked tokens, PoC evaluates validators across seven dimensions:

Dimension	Weight	Description
Staking	30%	Amount of QFC tokens staked
Compute	20%	Computational resources provided
Uptime	15%	Node availability and reliability
Accuracy	15%	Validation accuracy and correctness
Network	10%	Network quality and latency
Storage	5%	Storage capacity contributed
Reputation	5%	Historical performance and behavior

Contribution Score

Each validator's contribution score is calculated as:

Score = Σ (dimension_weight × dimension_score)

Where each dimension score is normalized between 0 and 1.

Example Calculation

Validator A:
- Staking:    0.8 × 0.30 = 0.240
- Compute:    0.9 × 0.20 = 0.180
- Uptime:     0.95 × 0.15 = 0.143
- Accuracy:   0.98 × 0.15 = 0.147
- Network:    0.85 × 0.10 = 0.085
- Storage:    0.7 × 0.05 = 0.035
- Reputation: 0.9 × 0.05 = 0.045
─────────────────────────────────
Total Score: 0.875

Block Producer Selection

Block producers are selected using a Verifiable Random Function (VRF) weighted by contribution scores:

1. VRF Generation: Each validator generates a VRF proof using the previous block hash
2. Weighted Selection: Selection probability is proportional to contribution score
3. Verification: Other nodes verify the VRF proof

P(selected) = contribution_score / total_contribution_scores

Epoch System

QFC operates in epochs:

• Epoch Duration: 100 blocks (~5 minutes)
• Validator Set Update: At epoch boundaries
• Score Recalculation: Every epoch

At the end of each epoch:

1. Contribution scores are recalculated
2. Validator set is updated (joining/leaving)
3. Rewards are distributed

Finality

QFC uses a two-phase commit for fast finality:

Phase 1: Proposal

• Block producer creates and broadcasts block
• Validators receive and validate the block

Phase 2: Voting

• Validators vote on the block (>2/3 required)
• Block is finalized when supermajority is reached

Finality time: < 0.3 seconds (single block confirmation)

Slashing

Validators can be slashed for malicious behavior:

Violation	Penalty
Double signing	5% stake
Prolonged downtime (>24h)	1% stake
Invalid block proposal	2% stake
Censorship (proven)	10% stake

Slashed tokens are burned (removed from circulation).

Rewards

Block rewards are distributed based on contribution:

validator_reward = block_reward × (validator_score / total_scores)

Additionally:

• Delegator Rewards: Distributed proportionally to delegated amount
• Commission: Validators take a commission (0-100%) from delegator rewards

Dynamic Weight Adjustment

In certain network conditions, dimension weights can be adjusted:

High Congestion

When transaction volume is high:

• Compute weight increases
• Network weight increases
• Staking weight decreases slightly

Attack Detection

When potential attacks are detected:

• Accuracy weight increases
• Reputation weight increases
• Quick response to malicious actors

Becoming a Validator

Requirements:

• Minimum stake: 10,000 QFC
• Reliable hardware (see Requirements)
• 99%+ uptime commitment

// Register as validator
await wallet.registerValidator(
  10,                    // 10% commission
  'my-validator',        // moniker
  parseQfc('10000')      // stake
);

Delegating

Anyone can delegate to validators:

// Delegate to validator
await wallet.delegate(
  '0xValidatorAddress',
  parseQfc('1000')       // minimum 100 QFC
);

// Check rewards
const delegation = await wallet.getDelegation('0xValidator');
console.log('Pending rewards:', formatQfc(delegation.pendingRewards));

// Claim rewards
await wallet.claimRewards();

Comparison with Other Consensus

Feature	PoC (QFC)	PoS (Ethereum)	DPoS (EOS)
Selection Criteria	Multi-dimensional	Stake only	Elected delegates
Validator Count	Unlimited	~500k	21
Finality	< 0.3s	~15 min	~0.5s
Energy Efficient	Yes	Yes	Yes
Decentralization	High	High	Medium

Security Properties

1. Sybil Resistance: Staking requirement prevents cheap identity creation
2. Nothing-at-Stake: Slashing makes attacking expensive
3. Long-Range Attacks: Checkpoint system prevents history rewriting
4. Censorship Resistance: Multi-dimensional scoring prevents monopoly

Next Steps

• Become a Validator
• Staking Guide
• Blockchain Basics