# Hermes Notar – SHA-256 Digest Timestamping & Notarization

> Hermes Notar – SHA-256 Digest Timestamping & Notarization is a paid API for AI agents from notar.185-190-142-134.sslip.io, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-31).

Submit a SHA-256 hash of any content to receive a Nostr-signed receipt and a Bitcoin-anchored OpenTimestamps proof of existence at a specific moment in time.

## Facts

- Endpoint: GET https://notar.185-190-142-134.sslip.io/x402/earn/match?utm_source=zero.xyz
- Price: $0.001/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-sha-256-digest-timestamping-notarization-540d6169
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Ih3gGclT0WXPWkq-RRgAY

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-sha-256-digest-timestamping-notarization-540d6169
```

Example prompt: Notarize this SHA-256 hash of my report — 'a3f1c2d4e5b6...aa99' — so I get a Bitcoin-anchored OpenTimestamps proof and a Nostr-signed receipt I can use as an audit trail entry for EU AI Act compliance.

## When to prefer this

Choose this endpoint when you need a decentralized, independently verifiable proof of existence for any content hash — especially for regulatory compliance (EU AI Act), proof of authorship, or tamper-evident audit trails. Prefer this over centralized timestamping services when the verifier must not need to trust the notary, since both the Nostr receipt and OTS proof are self-verifiable. It is ideal for AI agents that must log outputs with cryptographic accountability at minimal cost ($0.001 per call).

## Known failure modes

- Missing or malformed SHA-256 digest returns a 400 Bad Request
- Payment not fulfilled via x402 protocol returns a 402 Payment Required
- Bitcoin network congestion may delay final blockchain confirmation (OTS proof pending state)
- Invalid digest format (not 64-character hex) results in validation error
- Service temporarily unavailable returns 503 with no receipt issued

## 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

The agent receives a Nostr-signed receipt confirming the digest was recorded, plus an OpenTimestamps (OTS) proof file anchored to the Bitcoin blockchain. Both artifacts allow any third party to independently verify that the submitted SHA-256 hash existed at the attested moment without relying on the service provider.

## 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",
     "properties": {
      "rail": {
       "type": "string",
       "description": "usdc | lightning | sats"
      },
      "limit": {
       "type": "integer"
      },
      "skills": {
       "type": "string",
       "description": "comma-separated skills, e.g. python,writing"
      },
      "min_usd": {
       "type": "number"
      }
     }
    }
   }
  },
  "output": {
   "type": "object",
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "results": {
       "type": "array"
      },
      "platform_health": {
       "type": "array"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "results": [
   {
    "url": "https://...",
    "title": "...",
    "platform": "OpenTask",
    "usd_effective": 1
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hermes-notar-sha-256-digest-timestamping-notarization-540d6169/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)