# SatLedger RFC 3161 Timestamp Receipt

> SatLedger RFC 3161 Timestamp Receipt is a paid API for AI agents from api.satledger.org, paid per call via x402, $0.05/call, status unknown (last checked 2026-09-14).

Issues a single RFC 3161 cryptographic timestamp receipt anchored to a SHA-256 digest you provide, with no account or API key required.

## Facts

- Endpoint: POST https://api.satledger.org/x402/receipt
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/satledger-rfc-3161-timestamp-receipt-9b4d5105
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_x9NTs7q7gvJhOxKmLWCMn

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 satledger-rfc-3161-timestamp-receipt-9b4d5105 -d '<json body>'
```

Example prompt: I need an RFC 3161 timestamp receipt for this SHA-256 digest: a3f1e2d4b5c6789012345678abcdef01234567890abcdef1234567890abcdef12 — no account needed, just the receipt proving it existed right now.

## When to prefer this

Choose this endpoint when you need a standards-compliant RFC 3161 timestamp receipt without creating an account or managing API keys. It is ideal for one-off or automated timestamping workflows where privacy is paramount — only the hash is transmitted, never the underlying data. Prefer it over blockchain anchoring services when compatibility with PKI tooling, legal frameworks, or digital signature standards (e.g. PDF/A, CAdES, XAdES) is required. It is also the right choice when per-call micropayment pricing ($0.05 USDC) is preferable to subscriptions.

## Known failure modes

- Invalid digest format (not 64 hex characters) — returns 400 Bad Request
- Payment not included or insufficient — returns 402 Payment Required
- Digest field missing from request body — returns 400 with validation error
- Network or TSA upstream failure — returns 503 Service Unavailable
- Submitting more than 10 digests in the batch field — returns 400 with maxItems error

## How this service works

One RFC 3161 timestamp receipt over a digest you supply. No account and no API key: the response is the whole deliverable. Your data is never sent - only its hash - and nothing about the request is retained here.

## Output

An RFC 3161 timestamp receipt (a signed timestamp token from a Timestamp Authority) attesting that the supplied SHA-256 digest was presented at the recorded time. The receipt is self-contained and verifiable using standard PKI tooling without any further interaction with SatLedger.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "digest": {
   "type": "string",
   "pattern": "^[0-9a-fA-F]{64}$",
   "description": "SHA-256 of whatever you want timestamped, as 64 hex characters. Hash it yourself; the data never leaves your side."
  },
  "digests": {
   "type": "array",
   "items": {
    "type": "string",
    "pattern": "^[0-9a-fA-F]{64}$"
   },
   "maxItems": 10,
   "minItems": 1,
   "description": "Up to 10 SHA-256 hashes. Requires the batch price; the single price permits one."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/satledger-rfc-3161-timestamp-receipt-9b4d5105/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.satledger.org](https://www.zero.xyz/host/api.satledger.org/llms.txt)