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Remote-first MCP adapter for emitting Settlement Attestation Receipts; not a verifier.
About
Remote-first MCP adapter for emitting Settlement Attestation Receipts; not a verifier.
Remote endpoints: streamable-http: https://defaultverifier.com/mcp
Security Report
This MCP server for SAR verification contains multiple critical security issues that severely compromise its trustworthiness. The primary concern is a hardcoded private key used for cryptographic signing in a production verifier system (index.js), which defeats the entire purpose of cryptographic authenticity. Additionally, the server accepts arbitrary input for spec/output comparison without proper validation, creates an append-only trust log that could be exploited for denial of service, and lacks any authentication or authorization controls. While the verification logic in Python/Node examples is sound, the main signing server is fundamentally broken from a security perspective. Supply chain analysis found 7 known vulnerabilities in dependencies (0 critical, 5 high severity).
7 files analyzed · 18 issues found
Security scores are indicators to help you make informed decisions, not guarantees. Always review permissions before connecting any MCP server.
Permissions Required
This plugin requests these system permissions. Most are normal for its category.
How to Install & Connect
Available as Local & Remote
This plugin can run on your machine or connect to a hosted endpoint. during install.
Documentation
View on GitHubFrom the project's GitHub README.
DefaultVerifier — SAR Verification Infrastructure
SAR (Settlement Attestation Receipt) is a verification protocol that produces cryptographically signed receipts proving whether an AI agent completed a task according to its specification.
DefaultVerifier is a live SAR verifier implementation with a public receipt registry, metrics API, and explorer.
If it matters—Verify it.
Architecture
Understand the SAR stack and verification model:
Example Response
{ "witness": "SettlementWitness", "witness_version": "v0", "task_id": "example", "verifier_endpoint": "https://defaultverifier.com/verify", "witness_timestamp": "2026-01-01T00:00:00Z", "receipt_id": "...", "receipt": { "profile": "settlement-witness-verified-v0.2", "task_id_hash": "sha256:...", "verdict": "PASS", "reason_code": "CONDITION_SATISFIED", "ts": "...", "verifier_kid": "...", "counterparty": "0xABC...", "receipt_id": "sha256:...", "sig": "base64url:..." },
"_ext": { "agent_id": "0x123:demo" } }
Notes
- the receipt payload is issued under the
settlement-witness-verified-v0.2profile; verdicts arePASS,FAIL, orINDETERMINATE - when
counterpartyis present, it is included in signature scope and inreceipt_idderivation - retired signer keys remain valid for verifying receipts they historically signed;
verifier_kidin a receipt is historical evidence and is never rewritten - current signer lifecycle (which
kidis active vs. retired) is published athttps://defaultverifier.com/.well-known/sar-keys.json— treat that endpoint, not this README, as the source of truth for which key is currently active - this behavior is implemented and publicly verifiable via the live receipt and key endpoints
SAR Compatibility: This implementation follows SAR verification semantics, with an extended signed payload when counterparty is present.
Demo
Run a full end-to-end verification in ~2 minutes: DEMO.md
Quick Start
1. Create a receipt
curl -X POST https://defaultverifier.com/settlement-witness
-H 'content-type: application/json'
-d '{
"task_id":"quickstart-001",
"spec":{"checks":[{"kind":"field_equals","inputs":{"output_path":"$.result"},"expected":"hello"}]},
"output":{"result":"hello"},
"counterparty":"0x1234567890abcdef1234567890abcdef12345678"
}'
2. Fetch the receipt
curl https://defaultverifier.com/settlement-witness/receipt/<receipt_id>
Note: use the receipt_id from the returned receipt
3. Verify locally (Node)
cd examples/node-verify node verify.js receipt.json jwks.json
Examples
Node.js verification example: examples/node-verify/
Python verification example: examples/verify_receipt_python.py
Usage: python3 examples/verify_receipt_python.py <receipt_id>
API Endpoints
Create Receipt
POST /settlement-witness
Submits a task verification request and returns a signed SAR receipt.
Retrieve Receipt
GET /settlement-witness/receipt/{receipt_id}
Note: Use the receipt_id from the returned receipt (sha256:...) for retrieval.
Returns a previously issued receipt.
Wallet Receipt Explorer
GET /settlement-witness/receipts?wallet={address}
Returns recent receipts associated with a wallet address.
The public explorer is available at:
https://defaultverifier.com/explorer
This interface allows browsing recent receipts and wallet-indexed delivery history.
Public Verification Keys
https://defaultverifier.com/.well-known/jwks.json
Alternative (SAR protocol reference): https://defaultverifier.com/.well-known/sar-keys.json
Used to verify Ed25519 signatures for receipts.
Key Registry
https://defaultverifier.com/.well-known/sar-keys.json
Registry of verifier public keys referenced by verifier_kid.
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