How OC Stamp works

Two steps. First you sign. Then you anchor.

1. Sign

import { stamp } from '@orangecheck/stamp-core';

const env = await stamp({
    content: new TextEncoder().encode('release: v1.2.3 signed by Alice'),
    mime: 'text/plain',
    signer: {
        address: 'bc1qalice...',
        signMessage: async (m) => walletSignBIP322(m),
    },
    // Optional — reference an OC Attest attestation for "stake at signing"
    attest_ref:
        'a3f5b8c2d1e4f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1',
});

stamp() builds a canonical message with header oc-stamp, the SHA-256 of content, the MIME type, the signer's address, and — if provided — the Attest reference. The wallet signs the canonical bytes via BIP-322.

The envelope is a JSON blob:

{
    "id": "<sha256 of canonical message, base64url>",
    "version": "oc-stamp/v0",
    "signer": {
        "address": "bc1qalice...",
        "scheme": "bip322"
    },
    "content_hash": "<sha256 of content bytes, hex>",
    "mime": "text/plain",
    "attest_ref": "a3f5b8c2...",
    "issued_at": "2026-04-24T06:47:29.977Z",
    "sig": "<BIP-322 signature, base64>",
    "ots": null
}

The content itself is NOT included in the envelope — only its hash. You ship the envelope alongside the content (archive, filesystem, HTTP, whatever). A verifier re-hashes the content and checks against content_hash to prove the envelope commits to the same bytes.

This is intentional: envelopes stay small (~500 bytes) regardless of content size. A 4 GB video gets the same envelope a 40-byte string does.

2. Anchor

import { submitToCalendars, upgradeProof } from '@orangecheck/stamp-ots';

// Submit the envelope id to OpenTimestamps calendars
env.ots = await submitToCalendars(env.id);
// env.ots is now a "pending" OTS proof

submitToCalendars() POSTs the envelope's id bytes to one or more OTS calendars (alice.btc.calendar.opentimestamps.org, bob.btc.calendar.opentimestamps.org, etc.). The calendars batch many digests into a Merkle tree and publish the tree root to Bitcoin. At this point the proof is pending — you have a receipt that says "your digest is in a batch" but the batch hasn't hit the chain yet.

Once a Bitcoin block confirms, the proof can be upgraded:

// Minutes to hours later:
env.ots = await upgradeProof(env.ots, env.id);
// env.ots is now a "confirmed" proof chained to a specific Bitcoin block

The upgraded proof contains the Merkle path from your digest to the batch root, and the block header that included the batch root. Anyone holding the envelope + the proof + any honest Bitcoin node can verify:

The envelope was signed by the holder of the Bitcoin address (via BIP-322).
The envelope's id was included in a specific Bitcoin block at a specific height, so it cannot have been fabricated after that block.

Verify

import { verify } from '@orangecheck/stamp-core';

const result = await verify({
    envelope: env,
    content: contentBytes, // the raw bytes the envelope commits to
    verifyBip322: async (msg, sig, addr) => walletVerifyBIP322(msg, sig, addr),
    verifyOtsAnchor: myAnchorVerifier, // see /stamp/ots-anchor
});

if (result.ok) {
    console.log('Author:', result.signer.address);
    console.log('Content hash matched:', result.content_hash_ok);
    console.log('Anchored in Bitcoin block:', result.anchor?.block_height);
    console.log('Attest reference:', result.attest_ref);
}

verify() is pure — it does the crypto and delegates network calls (BIP-322 verification, OTS anchor resolution) to plug-in functions you provide. This keeps the core verifier offline-capable and lets you choose any block-header source.

Without the anchor

A stamp without ots is still useful — you have a signed statement binding content to an address. You just don't have a time-anchor. Anchor later, or skip it entirely if your use case doesn't need priority.

Publishing optional

Envelopes can be published to Nostr kind-30078 with d tag oc-stamp:<id> for durable public discovery, but it's optional. A stamp is a self-contained JSON blob; email it, embed it in a git commit message, put it in S3 — it verifies the same way.