# Hermes Notar — Bitcoin-anchored SHA-256 Timestamping

> Hermes Notar — Bitcoin-anchored SHA-256 Timestamping is a paid API for AI agents from notar.185-190-142-134.sslip.io, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-31).

Accepts a SHA-256 hash, returns a Nostr-signed receipt and an OpenTimestamps proof anchored to the Bitcoin blockchain as tamper-evident evidence of existence at a point in time.

## Facts

- Endpoint: GET https://notar.185-190-142-134.sslip.io/x402/stamp?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hermes-notar-bitcoin-anchored-sha-256-timestamping-5474c339
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_QFFbdqwKnQV7DXvXb6L4B

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability hermes-notar-bitcoin-anchored-sha-256-timestamping-5474c339
```

Example prompt: I need to timestamp and notarize the SHA-256 hash a4b3c2d1e5f6... of my AI report — give me a Bitcoin-anchored OpenTimestamps proof and a Nostr-signed receipt I can use as an audit trail.

## When to prefer this

Choose this endpoint when you need a trustless, publicly verifiable, decentralized proof that a piece of data existed at a specific moment in time — without disclosing the data itself. It is ideal for AI audit trails (EU AI Act), proof of authorship, proof of delivery, or any compliance scenario requiring a tamper-evident timestamp. Prefer it over centralized notarization services when verifiability without trusting the provider is required, and over manual OpenTimestamps tooling when you need an automated, pay-per-call API with a Nostr-signed instant receipt in addition to the Bitcoin anchor.

## Known failure modes

- Invalid or malformed hash (not 64 hex characters) returns an error — hash must match ^[0-9a-fA-F]{64}$
- Payment not completed via x402 protocol results in HTTP 402 and no receipt
- Bitcoin anchoring is initially 'pending' until the next OTS aggregation and block confirmation — final proof may take hours
- Nostr relay unavailability could delay receipt issuance
- Network timeout on the sslip.io host (IP-based domain, no SLA guarantee)

## How this service works

Send a SHA-256 digest of your output. Get an instant Nostr-signed receipt and a Bitcoin-anchored OpenTimestamps proof that anyone can verify without trusting us. Use it as proof of delivery, proof of authorship, or audit trail (e.g. EU AI Act logging).

## Output

A JSON object containing: a 'status' field (e.g. 'pending' while Bitcoin confirmation is awaited), a 'receipt' object with a Nostr event (kind 21040, pubkey) providing an instant cryptographic signature, an 'ots_file' URL to download the raw OpenTimestamps proof file, and a 'proof' URL to verify the anchoring — all tied to the submitted hash.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "hash"
     ],
     "properties": {
      "hash": {
       "type": "string",
       "pattern": "^[0-9a-fA-F]{64}$",
       "description": "SHA-256 digest (hex) of your data"
      },
      "nostr": {
       "enum": [
        "1"
       ],
       "type": "string",
       "description": "hash is a Nostr event id -> NIP-03 later"
      }
     }
    }
   }
  },
  "output": {
   "type": "object",
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "proof": {
       "type": "string"
      },
      "status": {
       "type": "string"
      },
      "receipt": {
       "type": "object"
      },
      "ots_file": {
       "type": "string"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "proof": "/proof?hash=...",
  "status": "pending",
  "receipt": {
   "kind": 21040,
   "pubkey": "7e801bc29b782a62fe60b4b4760a3f411c88a0ca5852f623aacea96b9fd4e77b"
  },
  "ots_file": "/proof.ots?hash=..."
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hermes-notar-bitcoin-anchored-sha-256-timestamping-5474c339/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from notar.185-190-142-134.sslip.io](https://www.zero.xyz/host/notar.185-190-142-134.sslip.io/llms.txt)