The 30-second summary
openssl rand is the OpenSSL CLI for emitting random bytes from the local OpenSSL CSPRNG. It's ubiquitous in shell scripts, CI pipelines, and ops one-liners (openssl rand -hex 32 to mint a token, anyone?). It's a great primitive — for jobs where nobody outside the script needs to verify the result.
Provable.io is the verifiable counterpart: every draw comes with a serverHash published in advance, so anyone with the seeds can re-derive the bytes after the fact.
Feature matrix
| Capability | Provable.io | openssl rand |
|---|---|---|
| Cryptographic strength | HMAC-SHA256 keyed stream | OpenSSL CSPRNG (seeded from OS entropy) |
| Reproducible from seed | Yes | No |
| Third-party verifiability | Yes | No — call is local |
| Pre-commitment | Yes | No |
| Latency | ~tens of ms (network) | Microseconds (local exec) |
| Auditable history | Yes — persisted, addressable by short ID | No |
| Dependency | HTTP | OpenSSL CLI / libcrypto |
| Best for | Public-audience draws that need proof | Shell scripts, CI tokens, local key material |
When openssl rand is the right answer
Stay with the CLI when the script is the only consumer:
- One-off shell tokens.
openssl rand -hex 32for a temporary password, signing key, or test fixture. - CI / build-time secrets. Seeding a test database, minting an ephemeral signing key.
- Local key material. Generating an HMAC key or an AES key without a network dependency.
When Provable.io is the right answer
A local CLI can't publish proof. The moment a result needs to be checked by someone who didn't run the command, Provable.io is the right shape:
- A public draw — raffle, jackpot, NFT trait reveal. See raffle picker and NFT trait generation.
- A re-derivable decision — A/B bucket, loot drop. See A/B bucketing.
- A scripted draw with an external audience — run
curlinstead ofopenssl rand; see the cURL quickstart.
Try it now
Same shell-script ergonomics as openssl rand -hex 32 — except the bytes carry a published proof.
curl "https://api.provable.io/api/bytes?clientSeed=vs-openssl-rand-demo&count=32&encoding=hex"FAQ
Is the network call worth it?
Only when verifiability matters. For one-off shell tokens, openssl rand wins on latency and dependency footprint every time. For published draws, the round trip is the price of proof.
Is openssl rand cryptographically sound?
Yes — OpenSSL's CSPRNG is the same primitive that backs most TLS in the world. The question is verifiability, not strength.
Can I script Provable.io from a Makefile?
Yes — see the cURL quickstart. Anywhere you can run curl, you can run a verifiable draw.