ElephStamp

A modern, object-oriented PHP library for OpenTimestamps. It lets you register a timestamp proof for a file with the public calendar servers and track/collect the completed proof once it has been anchored in the Bitcoin blockchain.

ElephStamp is a focused, partial port of the Python opentimestamps-client: it is not a line-by-line translation but an expressive PHP API. The .ots proof files it produces and reads are byte-for-byte interoperable with the reference tooling.

Scope

In scope

• Creating timestamp requests and submitting them to calendar servers.
• Following a proof's status and fetching the completed .ots once the calendars can provide a blockchain attestation.
• A built-in fake mode for tests and local/integration environments.

Out of scope (by design)

• No command-line tool — this is a library only.
• No on-chain verification. ElephStamp reports what a proof claims (e.g. the Bitcoin block height) but never talks to a Bitcoin node to verify it. Use a dedicated verifier for that.

Requirements

• PHP 8.5+ with the mbstring extension.
• symfony/http-client (pulled in automatically) for talking to calendar servers.

Installation

composer require condorcet-vote/elephstamp

Quick start

Stamp a file

use CondorcetVote\ElephStamp\ElephStamp;
use CondorcetVote\ElephStamp\FileToStamp;

$client = new ElephStamp();

$receipt = $client->stamp(FileToStamp::fromPath('contract.pdf'));

// Persist the proof next to your file.
$receipt->saveToPath('contract.pdf.ots');

echo $receipt->status()->name;        // "Pending"
echo $receipt->fileDigestHex();       // sha256 of contract.pdf

A freshly created timestamp is pending: the calendars have recorded your commitment but Bitcoin has not confirmed it yet (this usually takes a few hours).

All calendars are contacted concurrently, and a calendar that is unreachable or misbehaves is tolerated: a stamp succeeds as long as at least requiredCalendars of them accept it (see Configuration).

Follow up and collect the completed proof

use CondorcetVote\ElephStamp\ElephStamp;
use CondorcetVote\ElephStamp\Receipt;

$client = new ElephStamp();

$receipt = Receipt::fromPath('contract.pdf.ots');

if ($client->upgrade($receipt)) {
    // Something changed: persist the richer proof.
    $receipt->saveToPath('contract.pdf.ots');
}

if ($receipt->isComplete()) {
    echo 'Anchored in Bitcoin block ' . $receipt->bitcoinBlockHeight();
}

upgrade() performs a single polling pass and returns whether the proof changed. Call it again later while the receipt is still pending.

Describing what to stamp

FileToStamp has one explicit, typed constructor per source. Files are always hashed as a stream — their content is never loaded into memory in full.

use CondorcetVote\ElephStamp\FileToStamp;

FileToStamp::fromPath('invoice.pdf');                       // a file on disk
FileToStamp::fromSplFileObject(new SplFileObject('a.bin')); // an open handle
FileToStamp::fromContent('some in-memory string');          // raw bytes
FileToStamp::fromDigest($sha256);                           // a digest you already computed

fromDigest() uses the digest verbatim; its length must match the client's hash operation (SHA-256 by default).

Privacy nonce

By default a random nonce is mixed into the digest before it reaches a calendar, so the calendar never learns the real file hash. When linkability is acceptable — or desirable, e.g. so the commitment equals the file's plain SHA-256 and can be recomputed without the .ots — disable it:

FileToStamp::fromPath('public-release.zip')->withoutNonce();

Note that inside a stampMany() batch, a file stamped without nonce also exposes its plain digest in the sibling receipts of the batch (the merkle tree embeds each leaf's message into its neighbours' proofs) — not only to the calendars.

Stamping several files at once

stampMany() binds all files into a single merkle tree, so one calendar submission covers them, while each file still gets its own independent receipt.

$receipts = $client->stampMany(
    FileToStamp::fromPath('a.pdf'),
    FileToStamp::fromPath('b.pdf'),
    FileToStamp::fromPath('c.pdf'),
);

Reading a receipt

$receipt->status();               // Status::Pending | Status::Complete
$receipt->isComplete();
$receipt->isPending();
$receipt->fileDigest();           // raw digest bytes
$receipt->fileDigestHex();        // lower-case hex
$receipt->pendingCalendarUris();  // list<string> of calendars still to poll
$receipt->bitcoinBlockHeight();   // int|null (claimed, not verified)
$receipt->toBytes();              // the raw .ots content
$receipt->describe();             // human-readable proof tree (for inspection)

describe() renders the proof as an indented tree, handy for debugging:

file sha256 digest: da7badf6…f655
append d6c877a9…
sha256
 -> append 014870d0…
    sha256
    prepend f23482df…
    sha256
    pending attestation → https://finney.calendar.eternitywall.com
 -> …

Testing: fake mode

ElephStamp::fake() returns a fully offline client. Proofs are deterministic and the fake calendar lets you simulate Bitcoin confirmation, so you can test both the pending and complete states without any network.

use CondorcetVote\ElephStamp\ElephStamp;
use CondorcetVote\ElephStamp\FileToStamp;

$client = ElephStamp::fake();

$receipt = $client->stamp(FileToStamp::fromContent('hello world'));
$receipt->isPending();   // true

// Simulate Bitcoin confirming the commitment.
$client->fakeCalendar()->confirmAll(blockHeight: 812_345);

$client->upgrade($receipt);
$receipt->isComplete();          // true
$receipt->bitcoinBlockHeight();  // 812345

Confirm a specific receipt, or everything submitted so far:

use CondorcetVote\ElephStamp\Calendar\FakeCalendarClient;

$calendar = new FakeCalendarClient();
$client = ElephStamp::fake($calendar);

$receipt = $client->stamp(FileToStamp::fromContent('data'));

$calendar->confirm($receipt);  // confirm just this receipt
// or
$calendar->confirmAll();       // confirm every commitment submitted so far

Configuration

use CondorcetVote\ElephStamp\ElephStamp;

$client = new ElephStamp(
    calendarUrls: ['https://a.pool.opentimestamps.org', 'https://b.pool.opentimestamps.org'],
    requiredCalendars: 2, // the "m" of an m-of-n policy
);

Calendar URLs must be unique and use https (a plaintext connection would let a network attacker inject forged responses); the same goes for whitelist patterns. When requiredCalendars is omitted it defaults to 2 — like the reference client — or to 1 when a single calendar is configured.

Upgrade whitelist (security)

An .ots proof embeds the calendar URIs to poll when upgrading. Because a proof may come from an untrusted source, upgrade() only contacts hosts on an allowlist — otherwise a hostile proof could point the process at arbitrary hosts (an SSRF risk). The default covers the known public operators (*.calendar.opentimestamps.org, *.calendar.eternitywall.com, *.calendar.catallaxy.com). Override it when you use private calendars:

$client = new ElephStamp(
    calendarUrls: ['https://ots.internal.example'],
    upgradeWhitelist: ['https://*.internal.example'],
);

Host patterns accept shell-style globs; URLs with a query, fragment or credentials are always rejected.

Customising the HTTP client

The default transport is the Symfony HTTP client, hardened for calendar traffic: redirects are never followed, responses are capped at 10 kB, and requests time out after 10 s of silence (30 s in total). Tune the timeouts, or inject your own configured instance (proxy, retries, ...) when needed:

use CondorcetVote\ElephStamp\Calendar\HttpCalendarClient;
use CondorcetVote\ElephStamp\ElephStamp;
use Symfony\Component\HttpClient\HttpClient;

$calendarClient = new HttpCalendarClient(
    HttpClient::create(['proxy' => 'http://proxy.internal:3128']),
    timeout: 5.0,       // idle timeout, seconds
    maxDuration: 15.0,  // hard cap per request, seconds
);

$client = new ElephStamp(calendarClient: $calendarClient);

Exceptions

Every exception implements CondorcetVote\ElephStamp\Exception\ElephStampException:

• InvalidInputException — bad caller input (unreadable file, invalid options).
• SerializationException — malformed or unsupported .ots data.
• CalendarException — a calendar was unreachable or misbehaved.
• StampingException — too few calendars accepted a stamp (m-of-n not met).

License

MIT — see LICENSE.