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How RNG certification works in slots
Introduction: why slots are "a real accident"
RNG is the heart of any luck game. It turns spin into an unpredictable result, and its correctness ensures that the declared mathematics (RTP, variance) actually works. Certification is an independent check of the algorithm, its implementation and environment (assembly, logs, security policies) to eliminate bias and manipulation.
1) Which RNGs are used in online slots
Cryptographically strong PRNGs (often based on stream encryption/block ciphers in the counter): for example, AES-CTR/DRBG-like solutions.
Modern high quality PRNG (xoshiro/PCG) - sometimes used in combination with a crypto stirrer.
Hardware entropy (HWRNG) - as a source of culture/entropy, and not as the only generator in the prod.
Classic generators like Mersenne Twister are convenient for simulations, but in real slots they often prefer crypto-resistant schemes or a hybrid (entropy → DRBG → stream of numbers).
Key requirements: high periodicity, uniformity of distribution, lack of correlations, resistance to prediction by the output sequence.
2) Seeding and entropy refilling
Primary seed is formed from several sources: system entropy pools, HWRNG, timings, network noise.
Reseed by schedule/volume: the generator is periodically "backed up" with new entropy to exclude degradation and attacks by state.
Safe storage: seed/keys - in HSM or protected module; least privilege access; rotation and audit.
3) How RNG numbers turn into symbols on reels
1. RNG produces 128-/256-bit blocks or 32/64-bit words.
2. Numbers are scaled to the desired range (for example, drum tape indices) without offset: use rejection sampling instead of simple "mod N" to avoid "modulo-bias."
3. The results are mapped into ribbons/paytables, after which the outcome of the spin is considered and the game rules (wild, scatter, bonus, multipliers) are applied.
4) What an independent laboratory checks
Accredited laboratories (for example: GLI, BMM Testlabs, iTech Labs, eCOGRA, SIQ) are engaged in certification. Their focus is wider than "run a couple of tests" - this is an audit of the process.
4. 1. Algorithm and implementation
PRNG/DRBG description, period, internal status structure.
Seeding/refilling method, entropy sources, key protection.
No hidden code/parameter branches affecting outcome.
4. 2. Statistical tests
Sets: frequency tests, runs tests, serial/cumulative, spectral analysis, autocorrelation, basket distribution (χ ²), bit randomness.
Complex packages: NIST SP 800-22/90-series (part of the approaches), Dieharder/TestU01.
Criteria: fractions of passes in confidence intervals for large samples.
4. 3. Linking to game math
Verification of compliance of the actual RTP with the declared model (simulations on tens/hundreds of millions of spins).
Validation of reels/tables of payments and combinations, control of rare events (jackpots, features).
4. 4. Safety loop and operational practices
Version control (hash builds, code-signing), unchanging logs (who/when deployed).
Separation of roles (who can trigger release/rollback), 4-eye principle.
Monitoring and anomaly alerts; patch and hotfix policy.
4. 5. Documents at the exit
RNG certificate and/or game/version specific certificates.
Test protocols, parameters, sample sizes, results.
Non-conformance report and CAPA plan (corrections with deadlines).
5) Certification process: how it looks step by step
1. Teacher: the developer/provider transfers the source materials - descriptions of algorithms, builds, configs, payment tables.
2. White/black box: code/binary review, checksum comparison, analysis of generation and mapping paths.
3. Generator test: large random number samples, batteries of statistical tests.
4. Simulations of the game: running mathematics on a massive sample (RTP/volatility/distribution of winnings).
5. Information security audit and processes: logging, sending, access, storage of/seed keys.
6. Report and certificate: issuing a certificate for a specific version of the game/engine.
7. Markets and listing: publication in the laboratory/regulator register (if provided).
6) When recertification is needed
Any edit affecting:- RNG algorithm, culture/reside;
- reel belts/pay tables;
- RTP/volatility parameters
- Random number mapping key ↔ outcomes
- cryptographic libraries and assembly chain.
- Moving infrastructure (different environment/compiler/platform) - often requires at least regression tests and an updated report.
7) Online platform: server RNG vs client
Server RNG (provider/operator side): centralized control, seed/HSM protection, simple certification.
Client RNG (rarely in slots): requires a secure environment on the device and a complex verification scheme.
In online slots, the standard is a server RNG with signed artifacts and unchangeable logs.
8) How a player can tell the difference between "real" certification
Checklist:1. In the footer/in the Fair Play section, the laboratory, certificate number/identifier, version of the game are indicated.
2. The date/version in the certificate matches the version specified in the game/lobby.
3. RTP in the rules = RTP on the game card and in the report.
4. The laboratory has a public registry or verifiable page.
5. During updates, there is a changelog and an explanation of whether the update affects RTP/certification.
Red flags:- Blurred wording "certified in Europe" without specifics.
- Links lead to a shared site, not a certificate/registry page.
- Different RTP in different places, "quiet" patches without notifications.
9) What is important to the operator and provider
Build DevSecOps gates: without a valid certificate/hashes, the release does not go into production.
Maintain a registry of versions (SBOM, hashes, compilation metadata), store artifacts.
Use rejection sampling/canonical mappings, avoid modulo-bias.
Implement reseed policy and key storage in the HSM.
Publish transparent changelogs and certification pages to trust and reduce controversy.
10) Frequent misconceptions
"There is a license - no audit is needed": a license is a frame, an audit is proof that the implementation is fair.
"RTP can be changed under promo": any change to RTP/tapes is a new assessment and, as a rule, re-certification.
"PRNG can be hidden, it is a secret": implementation details can be confidential, but the laboratory is obliged to see and test them.
"Mod N is always ok": with large ranges and "non-multiple" N gives an offset; the correct method is rejection.
11) Mini-FAQ
How many spins are raced on RTP tests?
Tens and hundreds of millions - to see rare events and narrow confidence intervals.
Is it possible to "guess" the next outcome from history?
With the correct crypto scheme and seeding policy, no; the story does not reveal the state of the generator.
Why are certificates bound to a version?
Any patch can change the statistics/data path; certification - about a specific build.
RNG certification is not one test, but a system of guarantees: a high-quality generator + correct seeding + correct scaling + verifiable game mathematics + secure release and logging processes. Where all these elements are built and regularly confirmed by an independent laboratory, the player gets a predictably honest slot, and the operator gets less controversy, higher partner confidence and access to regulated markets.