# Proof Key

Use a proof key only when the method derives a publication slot, such as an
HTTPS path or DNS TXT owner. Descriptor `u` identifies envelope bytes, but does
not remove a method's separate publication requirement. DNS TXT uses `u` for
the envelope and a proof key for the DNS claim-digest location.

The key is public and is not a content hash or signature. Validate the retrieved
envelope independently.

## Inputs

Use the [domain separator](/implementers/claim-digest), selected authority,
normalized name's node, record type and key, and exact descriptor method.
All inputs must be known before retrieving the proof. Never obtain them from
the envelope you are trying to locate.

## Derivation

The exact type string is:

```text
ENSRecordVerificationProofKey(bytes32 domainSeparator,uint32 authorityVersion,address authority,bytes32 node,bytes32 recordTypeHash,bytes32 recordKeyHash,bytes32 methodHash)
```

```pseudocode
proofKeyTypeHash = keccak256(UTF8(proofKeyType))
recordTypeHash = keccak256(UTF8(recordType))
recordKeyHash = keccak256(UTF8(recordKey))
methodHash = keccak256(UTF8(method))

proofKey = keccak256(abi.encode(
    proofKeyTypeHash,
    domainSeparator,
    uint32(authorityVersion),
    address(authority),
    node,
    recordTypeHash,
    recordKeyHash,
    methodHash
))
```

Encode eight standard 32-byte ABI words, for a 256-byte preimage. Left-pad the
integer and address with zero bytes. Do not use packed encoding, textual hex,
JSON, or an EIP-712 `0x1901` prefix for this calculation.

The proof-key type is separate from the signed claim type. Empty record keys
use Keccak-256 of the empty byte string, not a zero hash.

## Publication Encodings

| Method              | Encoding of the 32-byte key                       |
| ------------------- | ------------------------------------------------- |
| HTTPS publication   | 64 lowercase hexadecimal characters, without `0x` |
| DNS TXT publication | 52 lowercase Base32 characters, without padding   |

DNS uses the [RFC 4648](https://www.rfc-editor.org/rfc/rfc4648.html) Base32
alphabet, rendered as `a-z2-7`. Do not Base32-encode the hexadecimal string.
The method owns the surrounding URL path or DNS name and its length checks.

## Stability

The key excludes `valueHash`, target, timestamps, signatures, and proof URI.
This allows renewing or replacing a proof at the same slot. A different target
can still change the complete URL or DNS owner where the slot is located.

Changing the authority, authority version, name, record selector, method, or
domain changes the key. Restoring all inputs restores the same key. It does not
supply ownership-generation tracking or permanent revocation.

## Test Vector

Use the same fixture as [Claim Digest](/implementers/claim-digest):

<a href="/vectors/common-claim-v1.json" download>
  claim and proof-key vector
</a>

. It includes each input hash and the full 256-byte preimage.

```text
proofKeyTypeHash = 0x996584489ccc072f5c54146ea3a0e61365e835b39d5d3fa7ffb5c33bdbc008b0
proofKey = 0xf10198b0fa04c7128a1cd77f08ce5d2437fc795dfa47dc3cff3203dfa73f0385
proofKeyBase32 = 6eazrmh2atdrfcq4257qrts5eq37y6k57jd5yph7gib57jz7aocq
```

Verify that changing only `issuedAt`, `validUntil`, or the record value leaves
the key unchanged while changing the claim digest. Changing the authority or
record key must change both. These are calculation checks, not live verification.