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x402-endpoints.onrender.com Proof-of-Existence Notarization
x402
x402-endpoints.onrender.com Proof-of-Existence Notarization is a paid API for AI agents from x402-endpoints.onrender.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).
Submit a SHA-256 hash (or short content) and receive a timestamped, Ed25519-signed proof-of-existence receipt confirming the artifact existed at a specific point in time.
Price / call$0.01
Success—
StatusUnknown
How this service works
Notarize a document or data hash for AI agents: submit a SHA-256 hash (or short content hashed server-side) and get a timestamped, Ed25519-signed proof-of-existence receipt, verifiable offline with no callback. Prove an artifact, agent output or decision existed at a point in time. Honest scope: this is a SIGNED proof-of-existence receipt, NOT a blockchain-anchored or eIDAS/RFC-3161 legal timestamp. The issuer never sees your content when you send only a hash.
Output
A timestamped, Ed25519-signed proof-of-existence receipt confirming the submitted hash (or server-side hash of submitted content) was recorded at the moment of the call. The receipt is verifiable offline with no callback required, and the server never sees raw content when only a hash is submitted. Note: this is a signed receipt, not a blockchain-anchored or eIDAS/RFC-3161 legal timestamp.
Example use cases
Example prompt
“Notarize this SHA-256 hash for me — a4f3c9d2e1b08765432109abcdef1234a4f3c9d2e1b08765432109abcdef1234 — and add the memo 'agent decision v1' so I have a signed proof it existed right now.”
Technical details
Endpoint
GEThttps://x402-endpoints.onrender.com/proof/notarizeWhen to prefer
Use this endpoint when you need a lightweight, cryptographically signed proof that a specific document, artifact, AI output, or decision hash existed at a particular point in time, and you do not require blockchain anchoring or legally recognized timestamps (eIDAS/RFC-3161). Ideal for AI agents that need to log and prove the existence of their outputs, decisions, or intermediate artifacts during a workflow without exposing the underlying content.
Side effects
- Hash does not match required 64-character hex format — returns validation error
- Both hash and content omitted — returns missing parameter error
- Content exceeds 100,000 character limit — returns payload too large error
- Service temporarily unavailable on Render cold start — returns 503 or timeout
- Payment not completed — returns 402 Payment Required
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"proof": {
"memo": "invoice #42",
"sha256": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
"notarized_at": "2026-07-02T12:00:00Z",
"hash_algorithm": "sha256",
"hashed_server_side": false
},
"cached": false,
"source": "Local Ed25519 proof-of-existence (no external source)",
"anchoring": {
"note": "Signed proof-of-existence receipt (Ed25519), NOT a blockchain-anchored timestamp.",
"method": null,
"anchored": false
},
"timestamp": "2026-07-02T12:00:00Z",
"disclaimer": "Signed proof that this issuer observed the hash at the stated time. NOT a blockchain-anchored or legal (eIDAS/RFC 3161) timestamp.",
"verification": {
"how": "Recompute sha256(content); confirm equals proof.sha256; ed25519-verify signature over canonical claims.",
"offline": true
},
"signed_receipt": {
"claims": {
"kind": "proof_of_existence",
"memo": "invoice #42",
"issuer": "x402-endpoints.onrender.com",
"sha256": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
"algorithm": "sha256",
"issued_at": "2026-07-02T12:00:00Z"
},
"algorithm": "ed25519",
"available": true,
"signature": "<hex>",
"public_key": "5b77...9f9d",
"canonicalization": "JSON sort_keys, separators (',',':'), UTF-8"
}
}
}Tags
x402
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