Verify Receipt

Verify an Ed25519 signed receipt produced by protect-mcp with @veritasacta/verify from npm. The check itself makes no network requests and needs no vendor lookup. npx downloads @veritasacta/verify@0.9.2 the first time it runs. For an offline machine, install it in the project first with npm install --no-save @veritasacta/verify@0.9.2, and npx then runs the local copy without network access.

Usage

/verify-receipt ./receipt.json

protect-mcp 0.7.4 appends receipts to ./receipts/receipts.jsonl, one per line. Save one line to its own file first, e.g., the newest one with tail -n 1 ./receipts/receipts.jsonl > receipt.json. Use /audit-chain to verify the whole file.

What This Command Does

1. Reads the receipt JSON file
2. Validates the structure (required fields, correct types)
3. Takes the public key from the second argument, or from the publicKey value in ./protect-mcp.key (the receipt does not hold a key)
4. Reconstructs the canonical form (JCS, RFC 8785)
5. Verifies the Ed25519 signature over the canonical bytes
6. Reports the result

Implementation

Run this in a shell:

PUB="${2:-$(node -p 'JSON.parse(require("fs").readFileSync("./protect-mcp.key")).publicKey')}"
npx @veritasacta/verify@0.9.2 "$1" --key "$PUB"

Where $1 is the receipt path provided by the user, and $2 is an optional public key in hex.

Expected exit codes

Exit	Meaning	Action
0	Valid receipt, signature verified	Report: "Verified. Receipt authentic."
1	Signature mismatch — receipt tampered	Report: "TAMPERED. Signature does not match payload."
2	Malformed receipt or missing key	Report: "Undecidable. The receipt is malformed or no public key was given."

What to Show the User

For a valid receipt:

Verified ✓

Request:     tu-1790427588265-c8x5
Tool:        Read
Decision:    allow
Signed at:   2026-09-26T12:59:48.265Z
Key ID:      generated

For a tampered receipt:

TAMPERED ✗

The signature does not match the payload. This receipt has been modified
since it was signed.

Request ID:  tu-1790427588265-c8x5
Checked against key: 0faf558a90dfbf88...

Possible causes:
- A field was edited after signing (most common)
- The signature was copied from a different receipt
- The wrong public key was given

Compare this receipt against a known-good copy to identify the altered field.

For a malformed receipt:

MALFORMED ✗

The file is not a valid Veritas Acta receipt. Missing or invalid fields:
<list the specific structural issues>

A protect-mcp 0.7.4 receipt includes: v, type, algorithm, kid, issuer,
issued_at, payload, signature.

References

• Receipt format: IETF draft-farley-acta-signed-receipts
• Verify CLI: @veritasacta/verify on npm
• All receipts: use /audit-chain to verify ./receipts/receipts.jsonl