What is an offline-verifiable receipt?

An offline-verifiable payment receipt is a digital record whose authenticity you can check from its own bytes, without calling back to the issuer or a central ledger. It matters because it gives you audit-proof, dispute-ready, agent-to-agent trust that survives network outages, vendor lock-in, and post-quantum threats.

In practice, it is a signed, canonicalised document whose signature and content hash form a self-contained proof. You verify it with open-source tools, offline, forever. No API, no subscription, no single point of failure.

How offline-verifiable receipts work

A receipt is offline-verifiable when three things are true:

1. Content-addressed: the receipt's identifier is its own cryptographic hash (sha256). Change one byte, the hash changes. This binds the receipt to its exact content.
2. Signed: the hash is signed with a key whose trust path is embedded in the receipt (X.509, PGP, or agent passport). The signature proves who issued it and that it has not been altered.
3. Canonicalised: the receipt is serialised under a deterministic rule (RFC 8785 JCS) so every verifier computes the same hash from the same logical content. No whitespace, no encoding drift, no ambiguity.

When you receive such a receipt, you: - parse its bytes, - extract the signature and trust path, - canonicalise the content under RFC 8785, - compute its sha256 hash, - verify the signature against the hash and trust path.

If all steps pass, the receipt is authentic. You do this offline, with no call to the issuer, no blockchain, no SaaS. The receipt is its own proof.

Why offline-verifiable receipts matter

Audit: immutable, portable, regulator-ready

Regulators (MiCA, EU AI Act, SEC) require tamper-evident records. A receipt you can verify offline is tamper-evident by construction. You can store it on any medium (cold storage, WORM, paper), move it across jurisdictions, and prove its integrity years later. No vendor can revoke or alter it. This is the gold standard for compliance archives.

Disputes: self-contained, court-admissible

In a dispute, the party with the verifiable receipt wins. Because the receipt is self-contained, you can present it in court without relying on a third-party API or ledger. The judge verifies it with open-source tools, offline. No "he said, she said" about API logs or blockchain forks. The receipt speaks for itself.

Agent-to-agent trust: no single point of failure

Agents (AI, bots, APIs) settle payments with x402. An x402 facilitator issues a receipt for every payment. If the receipt is offline-verifiable, the agent can verify it without calling back to the facilitator. This removes the facilitator as a single point of failure. Agents can settle offline, in air-gapped environments, or across blockchains. Trust is decentralised.

Post-quantum survival: signatures that last decades

Classical signatures (RSA, ECDSA) will break when quantum computers arrive. A receipt signed today with a classical signature will be unverifiable in 10 years. An offline-verifiable receipt can be re-anchored with post-quantum signatures (Falcon-1024, ML-DSA) without altering its content hash. The original receipt remains valid, and the re-anchored version is verifiable offline forever.

Do it with AlgoVoi

AlgoVoi's self-hosted facilitator (AV-RAILS) and open JCS (RFC 8785) canonicalisation substrate produce offline-verifiable receipts. Every x402 payment produces a receipt whose authenticity you verify offline, with no licence and no AlgoVoi in the trust path.

The receipts are: - content-addressed (sha256), - signed (Ed25519 or post-quantum hybrid), - canonicalised (RFC 8785), - verifiable with open-source tools.

Use the public API to issue receipts: https://api.algovoi.co.uk/compliance/attestation.

Start with the docs

Build agentic payments that produce offline-verifiable receipts. Start with the docs.