Fediverse Public Key Directory PHP Client

This is an implementation of the client-side component of the Public Key Directory specification, written in PHP. See fedi-e2ee/pkd-server-php for the reference implementation of the server-side component written in PHP.

Installation

composer require fedi-e2ee/pkd-client

Usage

<?php
use FediE2EE\PKD\ReadOnlyClient;
use FediE2EE\PKD\Crypto\PublicKey;

// Setup client
$directoryPublicKey = new PublicKey('public key goes here', 'ed25519');
$client = new ReadonlyClient('https://pkd.example.com', $directoryPublicKey);

// Fetch public keys with Merkle proof verification (recommended)
$publicKeys = $client->fetchPublicKeys('[email protected]');
var_dump($publicKeys); // array<VerifiedPublicKey>

// Fetch auxiliary data with Merkle proof verification (recommended)
// 'age' is an alias for the latest version; i.e., 'age-v1'.
$auxData = $client->fetchAuxData('[email protected]', 'age');
var_dump($auxData); // array<VerifiedAuxData>

Verified Methods (Recommended)

The fetch*() methods verify Merkle inclusion proofs, ensuring each key or auxiliary data item is properly committed to the PKD's append-only Merkle tree:

• fetchPublicKeys(string $actor) → VerifiedPublicKey[]
• fetchAuxData(string $actor, string $auxDataType) → VerifiedAuxData[]

These methods throw ClientException if proof verification fails.

Unverified Methods (For Troubleshooting Only)

[!WARNING] These APIs do not validate Merkle inclusion proofs. Use with caution!

If you need to fetch public keys or auxiliary data without verifying the Merkle inclusion proofs, these methods are available too:

• fetchUnverifiedPublicKeys(string $actor) → PublicKey[]
• fetchUnverifiedAuxData(string $actor, string $auxDataType) → AuxData[]

Hash Function Validation

The verified methods accept an optional $hashFunc parameter (default: 'sha256'). Only cryptographically secure hash functions are accepted: sha256, sha384, sha512, and blake2b.

Attempting to use any other hash function will throw a ClientException.