UVS: a draw's fairness as a fact you can recompute — not a certificate you trust

Constantin Razinsky — Sun, 14 Jun 2026 23:38:36 +0000

I've built casino slot machines and gaming systems for 15 years. I mostly stayed away from compliance, but once I had to write the official algorithm description for a certification lab. I made it technically precise, handed it over — and realized nobody read or verified it. The lab ticked the boxes, took the money, issued a paper certificate. Two hours later a hotfix could ship to production and void the certified hash, and nobody would notice. The industry runs on dead paper, not real-time verification.

And it isn't only casinos: any draw, lottery, gacha banner, school-place allocation or event-ticket raffle has the same hole. There's a "✓ Provably Fair" badge, a server seed, a hash — and almost nobody ever checks it, often including the operator.

UVS (Uncloned Verification Standard) moves the proof of fairness off trusted third-party certificates and onto something anyone can recompute themselves.

The invariant: a tier derived from evidence, not claimed

The core of the standard is one function, deriveTier. It assigns a draw a trust tier from the evidence actually attached, not from a badge:

🔴 — no anchor, bare seed;
🟡 — notary / self-anchor / a beacon binding without proof the commitment came first;
🟢 — a neutral-registry signature, or trail-immutability, or outcome-binding with a proven commitment.

No evidence, no green. The code decides, not a promise.

Honest scope first — the part most "provably fair" pitches skip

UVS proves that the published rules were followed on the published inputs using the published randomness. It does NOT prove the inputs themselves were honest: an operator can still enter phantom tickets or publish a prize pool that differs from what players were promised. UVS secures one link — the outcome — and secures it completely; guarding the inputs (and KYC, licensing) is a separate control. Better to say it up front than oversell.

Two branches, because randomness behaves differently by mechanic

uvLottery (draws / gacha) — can reach 🟢

One seeded permutation. Hash a server seed with a public drand round (quicknet, 3s ticks), score every entrant, sort, deal the published pool onto that order:

combinedSeed = SHA-256( serverSeed : drandRandomness )
score(id)    = SHA-256( combinedSeed : id )      // per participant

Sort by score (descending, ties by id), deal prizes top-down. Same inputs → the same list, on any machine, in any language, forever. No hidden state.

To stop the operator grinding seeds, the outcome binds to a drand round whose randomness doesn't exist yet at commit time. drand rounds are a deterministic function of time:

round = floor((now − genesis) / 3) + 1     // quicknet genesis = 1692803367

For 🟢 that isn't enough — you need a commitment anchor. The commitmentHash (without the round) is timestamped at two independent RFC-3161 TSAs (FreeTSA + DigiCert, different jurisdictions, in parallel), and the round is then derived from the proven stamp: R = roundAt(genTime)+1 — the first round strictly after the timestamp. So genTime < timeOfRound(R) holds by construction, and the operator never chooses R (nothing to grind). Verification is the spec's reference path:

openssl ts -verify -digest <commitmentHash> -in token.tsr -CAfile <ca>

"But a TSA is a trusted third party too." Yes — but a neutral one, and two in different jurisdictions make quiet collusion implausible. More importantly the whole chain is publicly re-derivable: refetch the round, re-run the permutation in any language, verify the token. You aren't asked to trust me; you're handed the inputs.

uvGame (interactive physics) — honest ceiling is 🟡

Input-seeded commit-reveal: the outcome depends on a committed server seed plus the player's real-time moves. There's no external beacon in the physics loop, so outcome-binding (and 🟢) is impossible by construction.

The "Uncloned" layer: a WASM engine built on the fly

The word "Uncloned" comes from here. The verification logic isn't baked in statically: per session, the registrar issues a regSeed, and the client builds a unique WASM module from it, in the browser, byte by byte.

buildWasm(regSeed) runs a deterministic LCG seeded by regSeed, draws a chain of 4–7 arithmetic steps (shifts + binary ops with random constants), then hand-emits a valid wasm binary — magic header 00 61 73 6d, the type/function/export/code sections, LEB128 numbers — exporting a compute(i32) -> i32:

function buildWasm(regSeed) {
  const lcg = new LCG(regSeed);
  const n = lcg.range(4, 7);
  const steps = Array.from({ length: n }, () => ({
    shiftOp:  SHIFT_OPS[lcg.range(0, SHIFT_OPS.length)],
    shiftAmt: 8 + lcg.range(0, 8),
    binOp:    BINARY_OPS[lcg.range(0, BINARY_OPS.length)],
    constVal: (lcg.next() | 1) | 0,
  }));
  // ...emit wasm sections + the function body in LEB128...
  return { bytes: new Uint8Array([0x00,0x61,0x73,0x6d, 0x01,0x00,0x00,0x00, /* ... */]) };
}

The client instantiates it, runs compute, gets a wasmResult; the registrar does the same with its regSeed and checks the result. Because the circuit is unique per session and derived from a seed, you can't pre-bake or stub it — to pass you must actually run the exact arithmetic the registrar emitted. That's the "uncloned" layer: not "trust our engine," but "here's exactly the engine we verify."

After a session the player hits ANCHOR, which notarizes the final game record at the same dual RFC-3161 TSAs — an immutable post-game ledger, honestly labeled 🟡. A 🟢 path via OpenTimestamps (Bitcoin trail-immutability) is coded but switched off until anyone needs it.

A note on the verifiers: the four byte-for-byte reference implementations (JS / Python / Java / C++) are for the draw; the physics game's determinism is checked by deterministic replay of the input log.

Architecture

The crypto runs on a backend (Docker on Render) — one host carries both the game registrar and the anchored draws. Endpoints: /commit (server seed → commitmentHash → ×2 RFC-3161 in parallel → R = roundAt(genTime)+1 from the proven stamp), /reveal (fetch the round, run the draw, return the 🟢 record + serverSeed + drand + anchor), /anchor-record (notary for a game record). Crucially the host verifies each RFC-3161 token itself (openssl ts -verify, roots fetched from the TSAs at build, not from the operator) before granting 🟢; the commit time used is the verified genTime, never the caller's claim. deriveTier reads the tier off the facts.

On latency — honestly

The anchored draw settles in a few seconds, and it isn't the crypto. The round it binds to is the first drand round after the proven timestamp (R = roundAt(genTime)+1), so the wait is one beacon tick (~3s): the randomness simply doesn't exist when the seed is fixed. That short wait IS the anti-grinding property, not overhead.

On "an LLM wrote this"

I'm a core Java developer; I know HTML/JS by hearsay and leaned heavily on LLMs for the browser and cloud parts. Normally that's a reason to distrust a security tool — except the whole point of UVS is that you don't have to trust the implementation: the result is independently recomputable from public inputs in four languages. Whether an LLM or I wrote the front end is irrelevant to whether a draw is fair. The protocol is the product; the code is one expression of it.

Try it

Everything is live, open (MIT) and decoupled:

Spec + verifiers (JS / Python / Java / C++): https://github.com/constarik/uvs (lives at https://uvs.uncloned.work)
/draw — one page, In-browser 🟡 (client-side) vs Anchored 🟢 via the backend: https://uvs.uncloned.work/draw
PADDLA — a physics arcade game: https://paddla.uncloned.work . Play, hit ANCHOR, verify the RFC-3161 token with openssl ts -verify.
SDK: npm i @constarik/uvs-sdk

I'd love a tear-down of deriveTier, the dual-TSA commitment, and the derived-R rule (R = roundAt(genTime)+1) — where does it break?

DEV Community: Constantin Razinsky