The 30-second summary
GCP Cloud KMS generateRandomBytes returns random bytes from Google's HSM infrastructure. Like AWS KMS, it's the right primitive when you need HSM-backed entropy with FIPS 140-2 attestation and you're operating inside GCP's trust boundary.
Provable.io is a commit-reveal API. The server publishes a hash of its seed in advance, then reveals it; anyone with the seeds can re-derive the result. It's the right shape when a third party has to audit the draw, not when you need certified-module bytes for key material.
Feature matrix
| Capability | Provable.io | GCP Cloud KMS random |
|---|---|---|
| Trust model | Re-derive from published seed + hash | Trust GCP-managed HSM |
| Verifiable to a third party | Yes | No |
| Pre-commitment | Yes | No |
| Reproducible from seed | Yes | No |
| Entropy source | HMAC-SHA256 over committed seeds | FIPS 140-2 validated HSM |
| Cost | Free up to per-account daily quota | Per-request KMS API charge |
| IAM / network surface | API key or anonymous | Requires GCP credentials & KMS permissions |
| Game primitives | dice, shuffle, weighted pick, distributions | Raw bytes only |
| Best for | Public-audience draws that need proof | HSM-sourced key material inside GCP |
When GCP Cloud KMS random is the right answer
Reach for Cloud KMS when HSM-backed entropy is the actual requirement:
- Generating cryptographic key material with FIPS 140-2 attestation.
- Compliance regimes that require certified-module random bytes.
- You're already integrated with Cloud KMS for the rest of your secret management.
When Provable.io is the right answer
Cloud KMS doesn't publish proofs — the bytes are private to your project. Reach for Provable.io when:
- The draw has an external audience who needs to check the outcome. See raffle picker.
- You want to avoid per-call IAM and billing. Provable.io's free tier covers most app workloads.
- You need richer primitives — see shuffle a deck.
Try it now
Equivalent to generateRandomBytes({ lengthBytes: 32 }) — with a published proof attached.
curl "https://api.provable.io/api/bytes?clientSeed=vs-gcp-kms-demo&count=32&encoding=hex"FAQ
Is one stronger than the other?
For practical purposes the bytes are indistinguishable. The choice is about trust model: trust a certified HSM (Cloud KMS) vs trust the open-source verifier (Provable.io).
Can I use both?
Yes — Cloud KMS for key material that has to stay inside your project, Provable.io for draws an outside party will audit.
What about AWS KMS?
Same shape of comparison — see vs AWS KMS GenerateRandom.