Craton Offline Receipt Verifier

• Status: public verification kit for craton.receipt.protocol.v1
• Runtime: no network calls, no package install, no Craton account required
• Use case: retained receipt + pinned JWKS bundle -> independent local verification

Craton receipts are designed to remain independently verifiable even if the Craton runtime is unavailable. This kit verifies a stored receipt locally with a pinned public key bundle. It does not call Craton, does not require a network connection, and does not send receipt data anywhere.

The verifier implements craton.receipt.protocol.v1 only. It verifies the Ed25519 signature over the exact decoded receipt.payload_b64 bytes before it parses or displays the signed payload.

Files

• verify.html - offline browser verifier with no external dependencies.
• verify.py - command-line verifier using only the Python standard library.
• examples/sample_receipt.json - a signed test receipt for this kit.
• keys/public_key.jwks.json - the public key bundle that verifies the sample receipt.

The included sample receipt and key are test fixtures. For production receipts, replace keys/public_key.jwks.json with the pinned public key bundle from:

https://cratonlayer.com/protocol/v1/jwks.json

Retain the receipt and the JWKS bundle together for audit records. Do not fetch a fresh JWKS later and treat it as proof of what was pinned when the receipt was created.

Browser Usage

1. Open verify.html from this folder. It can be opened directly from disk.
2. Paste a receipt JSON object into the receipt field. You may paste either the receipt itself, { "receipt": ... }, or a full boundary response that contains receipt.
3. Paste the public JWKS key bundle you retained with the receipt.
4. Select Verify receipt.

The page verifies the Ed25519 signature over the decoded receipt.payload_b64 bytes. Only after the signature is valid does it parse and display the signed payload.

Command-Line Usage

Verify the bundled sample:

python verify.py examples/sample_receipt.json --jwks keys/public_key.jwks.json

Verify a production receipt with a pinned production key bundle:

python verify.py path/to/receipt.json --jwks path/to/pinned-public-key.jwks.json

On success, the script prints a JSON report with verified: true, the selected kid, a SHA-256 hash of the signed payload bytes, and the decoded signed payload. On failure, it exits non-zero and prints verified: false with a reason.

Security Notes

• The sample receipt and bundled key are fixtures for testing this kit. They are not production keys.
• Production verification depends on a receipt plus the exact public JWKS bundle retained for that audit record.
• The verifier rejects unsupported signature algorithms, non-canonical Ed25519 point encodings, small-order Ed25519 points, and payloads that are not craton.receipt.protocol.v1.
• Signature verification is performed before payload parsing. Do not reserialize the payload JSON and verify a transformed representation.
• This repository intentionally contains no production private keys, API keys, customer data, runtime configuration, or Craton server code.

Repository Scope

This repository is intentionally narrow. It contains only the standalone offline verifier, a sample receipt fixture, and a sample public key fixture. It does not contain the Craton runtime, production signing keys, customer configuration, billing logic, or deployment configuration.

Verification Logic

The verification logic follows craton.receipt.protocol.v1:

1. Extract receipt.payload_b64, receipt.signature, and receipt.kid.
2. Select the public key in the JWKS whose kid matches the receipt.
3. Decode receipt.payload_b64 to bytes.
4. Decode receipt.signature and the selected Ed25519 public key.
5. Verify the signature over the decoded payload bytes exactly.
6. Do not reserialize JSON before verifying.
7. Parse the signed payload only after the signature is valid.

This is the basis for no-callback verification: a retained receipt plus a pinned public key bundle can be checked offline by auditors, counsel, engineers, or other authorized third parties.