Provably fair selections for games, loot boxes, and any randomized allocation.
Commit to a rule before the outcome is knowable. Verify every result trustlessly.

No server. No account. No trust required.

What It Does

When your game drops loot, runs a gacha pull, or makes any randomized selection — players have no way to know it was fair. They can only trust you.

@fairseal/commit eliminates that trust requirement. It creates a Committed Selection Receipt (CSR) — cryptographic proof that:

Your selection rule was locked before the randomness existed
The randomness came from a public, verifiable source (drand beacon)
Anyone can independently verify every step

Quick Start

npm install @fairseal/commit

Copy-paste runnable (Node.js ≥ 18, ESM or ts-node):

import { createCommitment, resolveCommitment, createReceipt, verifyReceipt } from '@fairseal/commit';

// 1. Commit to your rule BEFORE the outcome is knowable
const commitment = createCommitment({
  rule: JSON.stringify({ type: 'uniform', pick: 1 }),
  inputs: ['SSR_Dragon', 'SR_Phoenix', 'R_Shield', 'N_Sword'],
  revealAfter: 10, // seconds until the beacon round
});
// commitment.commitHash is now locked — can't be changed

// 2–3. Resolve: { wait: true } polls until the beacon round is available
//    (max ~15s by default — no manual sleep needed)
const resolution = await resolveCommitment(commitment, { wait: true });
// resolution.beaconRandomness = verifiable entropy from drand
// resolution.selection        = built-in rule result (e.g. one of your inputs)

// 4. Package as a portable receipt
const receipt = createReceipt(commitment, resolution);

// 5. Anyone can verify — no trust in you required
const proof = await verifyReceipt(receipt);
console.log(proof.status, resolution.selection);
// → "PARTIAL" + your selected item

Expected: a self-issued receipt that is not anchored on-chain verifies as status: 'PARTIAL' (precedence unattested) — the math and entropy check out, but timing isn't third-party provable. That is the expected result here, not a failure. Only INVALID means verification failed.

Prefer an explicit helper? waitAndResolve(commitment) ≡ resolveCommitment(commitment, { wait: true }).

How Operators Integrate

You keep your own drop-rate algorithm. Fairseal doesn't implement your game logic — it proves your commitment was made before the outcome.

import { createCommitment, resolveCommitment, createReceipt } from '@fairseal/commit';

// Your published loot table (legally required in many jurisdictions)
const LOOT_TABLE = {
  version: 'celestial-banner-v3.2',
  rates: { SSR: 0.006, SR: 0.051, R: 0.200, N: 0.743 },
  items: {
    SSR: ['Dragon_Blade'],
    SR: ['Phoenix_Staff', 'Thunder_Bow'],
    R: ['Iron_Shield', 'Wind_Cloak'],
    N: ['Wooden_Sword', 'Leather_Armor'],
  },
};

// Step 1: Commit to the loot table + player ID before the pull
const commitment = createCommitment({
  rule: JSON.stringify(LOOT_TABLE),        // your entire table, hashed
  inputs: [playerId, sessionId, pullNumber.toString()],
  revealAfter: 10,
});

// Step 2: Resolve (waits for the beacon round automatically)
const resolution = await resolveCommitment(commitment, { wait: true });

// Step 3: Use YOUR weighted algorithm with the verifiable entropy
const drop = yourWeightedPull(LOOT_TABLE, resolution.beaconRandomness);

// Step 4: Package receipt — player can verify everything
const receipt = createReceipt(commitment, resolution);

// Give the player: { drop, receipt }
// They can verify: the table was locked before the entropy,
// the entropy is real, and re-run your algorithm to check the drop.

What the player sees

🎰 You pulled: ✨ SR Phoenix Staff

📜 Verification:
   Loot table committed: ✅ (locked before randomness existed)
   Randomness source:    ✅ (drand round #31034840, independently verifiable)
   Timing verified:      ⚠️  (PARTIAL — no on-chain anchor)
   
   Receipt ID: de31f0f939d2efcc...
   Verify: https://verify.fairseal.io/de31f0f939d2efcc

Architecture

┌─────────────┐     ┌──────────────┐     ┌─────────────┐
│  Your Game   │     │    drand     │     │  Base Chain  │
│  Server      │     │  (public     │     │  (optional   │
│              │     │   beacon)    │     │   anchor)    │
│  1. Commit   │     │              │     │              │
│  2. Wait     │────▶│  3. Entropy  │     │              │
│  4. Resolve  │◀────│              │     │              │
│  5. Receipt  │     │              │     │  6. Anchor   │
└─────────────┘     └──────────────┘     └─────────────┘
       │                                        │
       │              ┌──────────┐              │
       └─────────────▶│  Player  │◀─────────────┘
                      │ (verify) │
                      └──────────┘

Your game server commits to the loot table and resolves the selection.
drand provides public, verifiable randomness (League of Entropy — Cloudflare, Protocol Labs, etc.).
Base chain (optional) anchors the commitment timestamp for third-party proof.
The player can independently verify every step. No trust required.

Verification Levels

Level	What it proves	How
PARTIAL	Math is correct, entropy is real	Free — `@fairseal/commit` only
VALID	Math + entropy + timing independently proven	On-chain anchor (self-anchor or Fairseal service)

PARTIAL = your players can verify the math. Good for trust-building.
VALID = a third party (regulator, auditor, dispute resolver) can prove timing. Required for compliance.

Need VALID? On-chain anchoring (anchorCommitment) is coming in v0.2. In the meantime, you can self-anchor the commitment.commitHash to any EVM chain. The Fairseal service will offer batched anchoring at ~100x lower cost.

Use Cases

Scenario	How CSR helps
Gacha / loot box	Every pull has a receipt. Players verify drops match published rates.
Boss loot drops	Drop table committed per encounter. No "ninja nerfing."
Matchmaking	Pairing algorithm committed. Players verify no favoritism.
Daily rewards	Reward distribution provably follows announced rules.
Tournament brackets	Bracket seeding provably random, not rigged.
NFT minting order	Mint queue provably fair — no insider front-running.

Regulatory Compliance

Drop-rate disclosure is legally mandated in key markets:

🇨🇳 China — required since 2017
🇹🇼 Taiwan — disclosure requirements added 2023
🇯🇵 Japan — kompu gacha banned outright
📱 Apple / Google — odds disclosure required for paid random items

CSR closes the gap: disclosure says what the rates should be; CSR proves every pull followed the disclosed rates.

API Reference

`createCommitment(opts)`

Creates a commitment bound to a future drand beacon round.

createCommitment({
  rule: string,          // your game logic (canonical JSON) — will be hashed
  inputs: string[],      // context: player ID, session, pull number, etc.
  revealAfter: number,   // seconds until the beacon round
  beacon?: string,       // default: 'drand:quicknet'
  salt?: Uint8Array,     // random if omitted
})

Returns: Commitment with commitHash, targetRound, ruleHash, etc.

`resolveCommitment(commitment, opts?)`

Fetches the beacon randomness and verifies the BLS signature.

resolveCommitment(commitment, {
  wait?: boolean,      // poll until the target round is available (default: false — throws if early)
  maxWaitMs?: number,  // wait budget when wait=true (default: 15000)
})

Returns: Resolution with beaconRandomness, verified, output, etc.

`waitAndResolve(commitment, opts?)`

Convenience wrapper for resolveCommitment(commitment, { wait: true }).

`createReceipt(commitment, resolution, anchor?)`

Packages everything into a portable CSR receipt.

Returns: CSReceipt — JSON-serializable, independently verifiable.

`verifyReceipt(receipt)`

Independent verification — recomputes every hash, re-fetches the beacon, checks everything.

Returns: VerificationResult with status ('VALID' | 'PARTIAL' | 'INVALID') and individual checks.

Performance

Benchmarked on Apple M-series, Node.js v26. Your game won't notice.

Operation	Time	Notes
Commitment creation	0.006ms	Local SHA-256. 170,000+/sec.
Beacon fetch (drand)	~200ms	Cloudflare CDN, global.
Resolve (fetch + derive)	< 1 sec	One HTTP call + local HMAC.
BLS verification	~150ms	Real BLS12-381 pairing check.
Receipt size	0.9 KB	Smaller than a PNG thumbnail.

Scale: Client-side, no server. 10M pulls/day is just ~116 requests/sec to public drand relays. Your game server is the only bottleneck — and Fairseal won't be it.

FAQ

Do I need to change my game logic?
No. You keep your existing drop-rate algorithm. Fairseal wraps it with a commitment and verification layer.

What if the drand beacon is down?
Graceful degradation — the selection is delayed, never corrupted. The library tries multiple relays (Cloudflare, Protocol Labs) with automatic failover.

Is this free?
The library is free and open source. PARTIAL verification is free. For VALID (on-chain anchored) verification, you can self-anchor (~$0.01/tx) or use the Fairseal service for batched anchoring at lower cost.

Can I use this without blockchain?
Yes. The library works entirely without blockchain. On-chain anchoring is optional — it's only needed for VALID (third-party provable) receipts.