# Proof Key

A **proof key** identifies a publication slot for a name, record, authority, and
method. Some methods use it to calculate where a proof must be published before
reading that proof.

For example, the HTTPS publication method uses:

```text
https://example.com/.well-known/ens-record-verification/<proof-key>
```

Separate keys let `alice.eth` and `bob.eth` publish proofs on the same website
without sharing a file. The `url` and `blog` records on one name also get
different keys.

## Three Different Values

| Value                | Purpose                                                        |
| -------------------- | -------------------------------------------------------------- |
| Discovery-record key | Finds the descriptor in ENS, such as `verification[text][url]` |
| Claim digest         | Identifies the complete signed statement                       |
| Proof key            | Identifies a predictable publication slot                      |

The proof key is public. It is not a secret, a hash of the proof file, or proof
that anyone approved a claim.

## When It Changes

The key includes the protocol's signing domain, authority version, authority
address, ENS node, record type, record key, and method. Changing any of these
inputs changes the key.

It excludes the record value and timestamps so the publisher can update or
renew a proof at the same slot. The full location can still change: moving a
URL record to another website changes the origin used with the key.

The verifier checks the complete claim after retrieval. An older proof at the
same slot cannot verify a different current value.

## When It Is Needed

HTTPS uses a proof key to locate the envelope. DNS TXT uses it to locate the
published claim digest, while `u` supplies the envelope separately.

A method that needs only the envelope at `u` has no additional publication slot
to derive. Inline envelopes also need no lookup, but a method can still require
a proof key for separate evidence, as DNS TXT does.

Including the authority gives a new owner a different slot, but does not
prevent an old proof from becoming usable if that owner later returns. The
[claim's validity rules](/docs/components/common-claim#changes-and-expiry) still apply.

## Implementer Guide

See [Proof Key](/implementers/proof-key) for the derivation, output encodings,
and test vector.