✅ Master Verifiable Randomness
Understand VRF, commit-reveal, and Chainlink integration
Generate provably fair random numbers on-chain
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You've learned how verifiable randomness enables provably fair applications on blockchain through cryptographic guarantees. Let's review the key concepts before testing your knowledge.
🎲 The Randomness Challenge
Blockchains are deterministic by design—every node must compute identical results. This makes true randomness impossible without external sources.
- •blockhash(): Vulnerable to miner manipulation (can withhold unfavorable blocks)
- •Oracles: Introduce trust assumptions (centralization risk)
- •VRF/VDF: Cryptographically provable randomness without trust
🔐 VRF (Verifiable Random Functions)
VRF generates pseudo-random outputs with cryptographic proofs. Oracle uses private key to compute randomness + proof; anyone verifies using public key.
- •Chainlink VRF: Industry standard, $10B+ secured, 12+ chains, ~$5-10 per request
- •API3 QRNG: Quantum randomness (ANU source), free to use, 5+ chains
- •Process: Request → Oracle generates (output, proof) → On-chain verification → Callback delivery
- •Security: Unpredictable, verifiable, unique, collision-resistant
🔒 Commit-Reveal Schemes
Two-phase protocol: participants commit to hashed values, then reveal actual values. Prevents changing choices after seeing others' inputs.
- •Phase 1: Submit H(value + salt) — commitment locks in choice
- •Phase 2: Reveal value + salt — contract verifies hash matches
- •Use cases: Gaming (poker, RPS), voting (private ballots), auctions (sealed bids), RANDAO (Ethereum)
- •Security: Require deposits to penalize non-reveals, enforce strict deadlines, use strong salts
⚡ Implementation Choices
Choose implementation based on security requirements, cost constraints, and latency tolerance:
- •Chainlink VRF: Best for most projects (medium complexity, high security, ~200k gas + $5-10 fee)
- •Commit-Reveal: Low-cost applications (only gas fees ~50k, requires multiple participants)
- •VDF: Maximum security scenarios (time-locked computation, high gas ~500k, slow)
🚀 Real-World Applications
Verifiable randomness powers billions in blockchain value across multiple sectors:
- •Gaming & Lotteries: $1B+ market, provably fair outcomes (Axie Infinity, PoolTogether)
- •NFT Minting: Fair launches, random traits (Azuki, Moonbirds used Chainlink VRF)
- •Validator Selection: Ethereum beacon chain RANDAO, unbiased rotation
- •DeFi Protocols: Liquidation order randomization, sampling mechanisms