Primes

Miller–Rabin, forty rounds, at the bit width you ask for.

numbers.prime · v1 · renderer text

14835490616671508111
10538098786465337959
17445624733399859783
17627307080433432071
10318148356124380727

Controls · from schema()

Bit width

8 256

A 2048-bit RSA key is two 1024-bit primes. This stops at 256 because bcmath does the modular exponentiation in software and the wait stops being interactive.

How many

1 20

Safe primes only

p where (p−1)/2 is also prime — what Diffie–Hellman wants. Rarer by another factor of ln(p), so the width is capped at 128 bits when this is on.

Prefer twins

Report whether p + 2 is also prime. Not a filter: twin primes thin out fast and searching for them at 64 bits would hang.

Show as

Entropy source

Picking a source changes the story on the receipt, never the quality: anything below class A is mixed with the OS CSPRNG before it reaches you. This result actually came from drand · League of Entropy.

There is no same-seed re-render here. Recomputing a secret from a kept seed is exactly the thing this generator refuses to make possible, so every change of parameters draws fresh entropy.

seed token withheld

Nothing to keep: no token is issued for a generator that makes secrets.

entropy in

16 bytes

stream used

4,104 bytes

rejections

duration

31,252 µs

bits

found

candidates tested

rejected by trial division

expected candidates per prime

22.20

rounds

false positive bound

4^-40, about 1 in 10^24 — far below the odds of the hardware getting the arithmetic wrong

exhausted

search budget

643

sensitive

yes

Seed receipt

Class B · Public beacon

drand round 6,465,850 — no single operator could have predicted this value.

Published openly — anyone can look this value up after the fact.

source: drand · League of Entropy
observed: 2026-09-14T17:22:17+00:00
latency: 337ms
mixed with: csprng — always

https://api.drand.sh/public/6465850 ↗

No permalink

This generator makes secrets, so it is never given a shareable link. A password with a replayable URL is not a password — anyone holding the link could recompute it byte for byte, forever. The seed token is discarded the moment the response is written; nothing here is stored, logged or recoverable.

seed · withheld by design · numbers.prime is marked sensitive

This page and /api/v1/g/numbers.prime run the same code. There is no private endpoint.

Primes

Result

Measurements

Seed receipt

No permalink