# Akashi Notari Blockchain Proof of Existence

> Akashi Notari Blockchain Proof of Existence is a paid API for AI agents from anchor.akashi-notari.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-10).

Records a SHA-256 file hash on the Base blockchain to create an immutable, timestamped proof of existence without uploading the file.

## Facts

- Endpoint: POST https://anchor.akashi-notari.com/anchor?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-10
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/akashi-notari-blockchain-proof-of-existence-df75a548
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__cSpyidfWiaCXgam0Wf6-

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 akashi-notari-blockchain-proof-of-existence-df75a548 -d '<json body>'
```

Example prompt: I need to prove that my contract draft existed today — can you anchor the SHA-256 hash be44340d151cbfa7a5dc59b579dd6632fb0891b573f8fdc927264309a3b168f0 on Akashi Notari, recording it under the filename 'contract-draft-v1.pdf'?

## When to prefer this

Choose this endpoint when you need a cheap ($0.01 USDC), privacy-preserving, on-chain proof of existence for any file — the file itself is never transmitted, only its hash. Ideal for legal documents, intellectual property, compliance records, or any scenario requiring an immutable timestamp verifiable on Base blockchain. Prefer over centralized notarization services when trustlessness and decentralization matter, and over full-document blockchain storage when privacy is required.

## Known failure modes

- Invalid or malformed SHA-256 hash (not 64 hex characters) returns an error
- Payment failure via x402 protocol prevents anchoring
- Network or RPC issues with Base blockchain cause transaction failure
- Duplicate hash anchoring may succeed but creates a new separate transaction rather than deduplicating
- Filename field too long or containing unsupported characters may be rejected

## How this service works

Proof of existence for any file. The SHA-256 hash is written on-chain on Base and the block time becomes the proof. The file never leaves its owner.

## Output

Returns a JSON object confirming the anchor was recorded, including: the original SHA-256 hash, the Base blockchain transaction hash (txHash), the optional filename, a Unix timestamp of when it was anchored, and a certificateUrl linking to a human-readable certificate page on akashi-notari.com.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "hash": {
   "type": "string",
   "description": "SHA-256 of the file, 64 hex characters"
  },
  "filename": {
   "type": "string",
   "description": "Optional name to record with the hash"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "hash": "be44340d151cbfa7a5dc59b579dd6632fb0891b573f8fdc927264309a3b168f0",
  "txHash": "0xd01d3e019906321b7d410538aebb696dec806df1099756ec85ac7b2da91df7fc",
  "filename": "report.pdf",
  "timestamp": 1763105659,
  "certificateUrl": "https://akashi-notari.com/certificate/?chain=base&hash=0xd01d3e019906321b7d410538aebb696dec806df1099756ec85ac7b2da91df7fc"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/akashi-notari-blockchain-proof-of-existence-df75a548/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from anchor.akashi-notari.com](https://www.zero.xyz/host/anchor.akashi-notari.com/llms.txt)