# Reading a receipt

Every result carries a receipt: an Ed25519 signature over the BLAKE3 digest of the RFC 8785 canonical text of the request and of the result without its receipt. The command line signs with the user's key; the job service signs with its own, which `GET https://wai.transaction.science/quantum-jobs/v1` publishes.

```sh runnable
wai-quantum run prog.qasm --json > job.json
wai-quantum verify job.json        # signature VALID, and the signer's did:key
```

A result still verifies after any JSON reader has carried it. Change one number, in the request or the result, and it no longer does.

## What a job says

- `method` and `why`: the method that ran, and why the planner chose it.
- `result.accuracy.class`: `bit-exact` (the same bits on every machine), `exact` (only double-precision rounding), `bounded` (a bound on the error beside each value), `single` (single precision, on a GPU), `estimate` (with a standard error) or `heuristic` (with the method's own error estimate, not a bound). `wai-quantum docs methods` lists them.
- `result.counts`: seeded samples, keyed by the classical bits with the highest bit first. `expectations` and `amplitudes` are as asked.
- `result.energy`: on the service, the CPU energy of the job's process as the kernel counts it, with its uncertainty and what it leaves out. On the command line it is `unmetered`, with the reason.
- `result.receipt.key`: the key that signed it.

## The two receipts of `wai-quantum test`

- `receipts/NAME.run.json` is the run, in the job's form above.
- `receipts/NAME.intent.json` is the check. Its request holds the program, the run, each intent with every reference's text, and the run's receipt digest. Its result holds each verdict and whether all hold. `wai-quantum verify` checks it the same way.

## What a receipt shows

It shows that this key signed this request and this result, and anyone can rerun the request to compare. It does not show who holds the key, nor that the physics is right: the accuracy class and the intent's verdict say how far the numbers can be trusted.