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Run npx skillmds@latest add egorfedorov/rng-crypto-specialist in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

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Is Rng Crypto Specialist free to use?

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Who published Rng Crypto Specialist?

egorfedorov (@egorfedorov) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Rng Crypto Specialist by egorfedorov

Name: Rng Crypto Specialist
Author: egorfedorov

Rng Crypto Specialist

Design, implement, and audit provably fair RNG and cryptographic seed workflows for casino games. Use when defining commit-reveal architecture, server/client seed lifecycle, nonce progression, hash/HMAC outcome derivation, bias-free range mapping, fairness transcript verification, or cryptographic release sign-off evidence.

egorfedorov Updated Sep 17, 2026

File contents

RNG Crypto Specialist

Use this skill to make RNG behavior reproducible, tamper-evident, and independently verifiable.

Workflow

Define fairness contract before implementation.

Specify game outcomes that are RNG-derived, transcript fields, and reveal timing.
Set immutable rules for server seed rotation, client seed changes, and nonce increments.
Declare what players can verify pre- and post-reveal.

Choose cryptographic primitives and transcript schema.

Prefer SHA-256 commitments and HMAC-SHA256 outcome derivation unless the system requires otherwise.
Store canonical transcript fields: serverSeedHash, serverSeed (after reveal), clientSeed, nonce, gameId, mode, and outcome.
Define exact string/byte serialization and encoding rules to avoid replay mismatches.

Enforce bias-free outcome mapping.

Derive randomness from deterministic crypto material only.
Convert random integers to bounded outcome ranges with rejection sampling.
Reject modulo-only mapping when 2^n is not evenly divisible by range size.

Implement seed and nonce lifecycle controls.

Treat server seed as secret until reveal, then rotate immediately after reveal window.
Keep per-session or per-player nonce monotonic and gap-free.
Block replay or out-of-order nonce acceptance at API boundaries.

Verify transcripts with deterministic tooling.

Recompute commitment hashes from revealed server seeds.
Recompute expected outcomes from serverSeed, clientSeed, and nonce.
Treat hash mismatches, nonce reuse, or outcome mismatches as hard blockers.

Produce cryptographic sign-off package.

Deliver algorithm specification, sample transcripts, verification command outputs, and open risks.
Include exact patch plan with file paths for any fixes.

Commands

python3 scripts/verify_provably_fair.py \
  --server-seed "<secret>" \
  --client-seed "<client>" \
  --nonce 0 \
  --range-max 10000

python3 scripts/verify_provably_fair.py \
  --input <transcript.jsonl> \
  --default-range-max 10000

Treat non-zero exits as blocker findings.

Output Contract

When handling RNG crypto tasks, return:

Protocol Summary: commit-reveal flow, primitives, serialization, and rotation policy.
Verification Findings: pass/fail for commitments, outcomes, nonce monotonicity, and bias handling.
Patch Plan: exact files/functions to change and why.
Evidence: commands run and key outputs.
Residual Risks: unresolved issues preventing sign-off.

References

references/workflow.md: end-to-end implementation and audit procedure.
references/crypto-primitives.md: approved primitives, mappings, and pitfalls.
references/signoff-template.md: concise report structure for handoff.

Execution Rules

Keep pre-reveal server seeds confidential; never log plaintext secrets in production traces.
Freeze canonical serialization and test vectors before cross-language implementation.
Require rejection sampling for bounded integer mapping unless divisibility is guaranteed.
Mark any unverifiable outcome path as non-compliant.

---name: rng-crypto-specialistdescription: Design, implement, and audit provably fair RNG and cryptographic seed workflows for casino games. Use when defining commit-reveal architecture, server/client seed lifecycle, nonce progression, hash/HMAC outcome derivation, bias-free range mapping, fairness transcript verification, or cryptographic release sign-off evidence.---# RNG Crypto SpecialistUse this skill to make RNG behavior reproducible, tamper-evident, and independently verifiable.## Workflow1. Define fairness contract before implementation.- Specify game outcomes that are RNG-derived, transcript fields, and reveal timing.- Set immutable rules for server seed rotation, client seed changes, and nonce increments.- Declare what players can verify pre- and post-reveal.2. Choose cryptographic primitives and transcript schema.- Prefer `SHA-256` commitments and `HMAC-SHA256` outcome derivation unless the system requires otherwise.- Store canonical transcript fields: `serverSeedHash`, `serverSeed` (after reveal), `clientSeed`, `nonce`, `gameId`, `mode`, and `outcome`.- Define exact string/byte serialization and encoding rules to avoid replay mismatches.3. Enforce bias-free outcome mapping.- Derive randomness from deterministic crypto material only.- Convert random integers to bounded outcome ranges with rejection sampling.- Reject modulo-only mapping when `2^n` is not evenly divisible by range size.4. Implement seed and nonce lifecycle controls.- Treat server seed as secret until reveal, then rotate immediately after reveal window.- Keep per-session or per-player nonce monotonic and gap-free.- Block replay or out-of-order nonce acceptance at API boundaries.5. Verify transcripts with deterministic tooling.- Recompute commitment hashes from revealed server seeds.- Recompute expected outcomes from `serverSeed`, `clientSeed`, and `nonce`.- Treat hash mismatches, nonce reuse, or outcome mismatches as hard blockers.6. Produce cryptographic sign-off package.- Deliver algorithm specification, sample transcripts, verification command outputs, and open risks.- Include exact patch plan with file paths for any fixes.## Commands```bashpython3 scripts/verify_provably_fair.py \ --server-seed "<secret>" \ --client-seed "<client>" \ --nonce 0 \ --range-max 10000python3 scripts/verify_provably_fair.py \ --input <transcript.jsonl> \ --default-range-max 10000```Treat non-zero exits as blocker findings.## Output ContractWhen handling RNG crypto tasks, return:1. `Protocol Summary`: commit-reveal flow, primitives, serialization, and rotation policy.2. `Verification Findings`: pass/fail for commitments, outcomes, nonce monotonicity, and bias handling.3. `Patch Plan`: exact files/functions to change and why.4. `Evidence`: commands run and key outputs.5. `Residual Risks`: unresolved issues preventing sign-off.## References- `references/workflow.md`: end-to-end implementation and audit procedure.- `references/crypto-primitives.md`: approved primitives, mappings, and pitfalls.- `references/signoff-template.md`: concise report structure for handoff.## Execution Rules- Keep pre-reveal server seeds confidential; never log plaintext secrets in production traces.- Freeze canonical serialization and test vectors before cross-language implementation.- Require rejection sampling for bounded integer mapping unless divisibility is guaranteed.- Mark any unverifiable outcome path as non-compliant.

Frequently asked questions