twzrd-receipt-verifier 1.0.3

Standalone offline verifier for TWZRD AO-Receipt V5 (Ed25519-signed keccak256 leaf). No trust in TWZRD servers or code.

TWZRD Receipt Verifier (standalone)

Verify a TWZRD AO-Receipt V5 offline, trusting nothing from TWZRD's servers or codebase - only the receipt, TWZRD's published public key, and two widely-audited crypto libraries.

A TWZRD trust receipt has two layers:

1. Tamper-evidence - a keccak256 leaf over the receipt's preimage fields.
2. Authenticity - an Ed25519 signature over the leaf bytes, made with TWZRD's dedicated receipt-signing key.

This tool recomputes the leaf and checks the signature against the published key. If it says VALID, the receipt was authored by TWZRD and was not altered. Unsigned, wrong-key, or tampered receipts fail.

Where this fits: the agent trust loop

This verifier is the last step of the x402 trust rail an agent runs before and after it spends:

1. Discover a model/provider - wzrd-client (PyPI) or @wzrd_sol/sdk (npm)
2. Preflight the seller wallet, free - POST https://intel.twzrd.xyz/v1/intel/preflight (or MCP get_readiness_card_tool)
3. Pay with a signed receipt - GET https://intel.twzrd.xyz/v1/intel/trust/{seller} (0.05 USDC, x402)
4. Verify the receipt offline - this package (trust nothing but the bytes + the public key)

# zero-install: verify a receipt straight from the published package
npx twzrd-receipt-verifier receipt.json --pubkey 9V6Pn19kiUA5Rn6JpQfNduanvGt2aXGwsarosNfa2Ldf

The published signing key

field	value
algorithm	ed25519
key_id	twzrd-receipt-ed25519-v1
public key (base58)	9V6Pn19kiUA5Rn6JpQfNduanvGt2aXGwsarosNfa2Ldf

Also published, machine-readable, at:

• https://intel.twzrd.xyz/.well-known/x402 → receipt.signature.public_key
• https://intel.twzrd.xyz/openapi.json → x402.receipt.signature.public_key
• the MCP card agent-intel-mcp-card.json → receipt_signing.public_key

Most paranoid mode: pin the key out-of-band with --pubkey instead of fetching it, so you never trust the live endpoint to tell you which key to trust.

Get a receipt to verify

Any TWZRD V5 receipt works. To mint a fresh one, pay the trust endpoint (x402, 0.05 USDC on Solana mainnet) - e.g. via AgentCash:

npx agentcash@latest fetch https://intel.twzrd.xyz/v1/intel/trust/<PUBKEY> > resp.json
# the receipt is the `twzrd_receipt` object in the response

The receipt object looks like:

{
  "version": "v5",
  "leaf": "0x...",
  "preimage": { "domain": "TWZRD:AO_REPUTATION_RECEIPT_V5", "agent_id": "...", "score": 15, "...": "..." },
  "signature": "base58 ed25519 sig",
  "signing_pubkey": "9V6Pn19kiUA5Rn6JpQfNduanvGt2aXGwsarosNfa2Ldf",
  "key_id": "twzrd-receipt-ed25519-v1",
  "signing_alg": "ed25519"
}

Python

pip install pynacl pycryptodome     # libsodium Ed25519 + original Keccak-256

# fetch the published key and verify:
python verify_twzrd_receipt.py receipt.json

# pin the key out-of-band (recommended):
python verify_twzrd_receipt.py receipt.json --pubkey 9V6Pn19kiUA5Rn6JpQfNduanvGt2aXGwsarosNfa2Ldf

# also confirm a tampered copy FAILS:
python verify_twzrd_receipt.py receipt.json --self-test

# from stdin:
cat receipt.json | python verify_twzrd_receipt.py -

Node

npm install                          # tweetnacl + js-sha3 + bs58

node verify_twzrd_receipt.js receipt.json
node verify_twzrd_receipt.js receipt.json --pubkey 9V6Pn19kiUA5Rn6JpQfNduanvGt2aXGwsarosNfa2Ldf --self-test
cat receipt.json | node verify_twzrd_receipt.js -

Both exit 0 on VALID, 1 on INVALID.

What it checks (and the exact layout)

The keccak256 leaf preimage is a strict little-endian, length-prefixed concat (reproducible in any language):

domain            = "TWZRD:AO_REPUTATION_RECEIPT_V5"   (or ...ATTENTION... for attention receipts)
agent_id          = u16_le(len(utf8)) || utf8 bytes
score             = u16_le
confidence_bps    = u16_le
timestamp_unix    = u64_le
payer             = 32 bytes  (base58-decoded pubkey, or sha256(marker) for synthetic payers)
settlement_anchor = 32 bytes  (last 32 bytes of the utf-8 settlement_tx string, or 32 zero bytes)

leaf      = keccak256(domain || agent_id || score || confidence_bps || timestamp_unix || payer || settlement_anchor)
signature = Ed25519_sign(receipt_signing_key, leaf_bytes)

The verifier:

1. recomputes leaf from the preimage and compares it to receipt.leaf,
2. confirms receipt.signing_pubkey (if present) equals the trusted key,
3. verifies the Ed25519 signature over the 32 leaf bytes against the trusted key.

VALID requires all three. The settlement_tx in the preimage is an on-chain Solana signature you can independently check for ground truth.

Trust assumptions

You trust: the receipt you were given, the published public key (ideally pinned), and the crypto libraries (PyNaCl/libsodium, pycryptodome; tweetnacl, js-sha3). You do not trust TWZRD's API, database, or this repository's other code. Swap the libraries for your own if you prefer - the byte layout above is the whole spec.