Proof of work

The browser spent about a second of CPU on this request, on a 16-bit hash puzzle.

What it attests

The browser found a number so that SHA-256("<digest>:<number>") starts with 16 zero bits. The digest is unique to one request, so nothing can be computed in advance. A solution is good for one request only.

What it does not attest

It does not tell a human from a program. It only shows that the request had a cost.

What it learns

Only the request digest. It stores nothing.

How to list it

attestations: {
  'not-a-robot': { label: 'I am not a robot', providers: ['https://attest.triauth.org/proof-of-work'] }
}

The signature comes from proof-of-work@attest.triauth.org. Its signed metadata carries { bits: 16 }, so a website can set its own threshold.