# SHA-256 Hash & HMAC Timestamp Audit Seal

> SHA-256 Hash & HMAC Timestamp Audit Seal is a paid API for AI agents from api.ibancheck.co.uk, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-13).

Generates a cryptographic SHA-256 hash and HMAC timestamp audit seal for a JSON payload or base64-encoded file, creating a tamper-evident proof of data at a specific moment in time.

## Facts

- Endpoint: POST https://api.ibancheck.co.uk/api/hash-timestamp?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/sha-256-hash-hmac-timestamp-audit-seal-2fd1f653
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8TgM788r_MfrzH5gHE4yv

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 sha-256-hash-hmac-timestamp-audit-seal-2fd1f653 -d '<json body>'
```

Example prompt: Create a cryptographic SHA-256 hash and HMAC timestamp audit seal for this JSON payload — I need a tamper-evident record proving this data existed unchanged right now: {"orderId":"ORD-9921","amount":450.00,"currency":"EUR","action":"approved"}

## When to prefer this

Choose this endpoint when you need a lightweight, pay-per-call cryptographic audit seal without standing up your own hashing infrastructure — especially useful for AI agents that need to produce tamper-evident logs of their actions, for compliance workflows requiring proof-of-existence, or when you need both a SHA-256 content hash and an HMAC timestamp in a single call. Pairs naturally with the sibling hash-verify endpoint for later tamper detection.

## Known failure modes

- Empty or missing payload and fileBase64 fields returns a validation error
- Malformed base64 encoding for fileBase64 causes decoding failure
- Oversized payloads may be rejected or time out
- Network errors or service unavailability return HTTP 5xx
- Invalid JSON structure in payload object results in parse error

## How this service works

Enterprise microservice and autonomous AI agent hub: ISO 13616 IBAN (#6), Romanian CUI Modulo-11 & EU VIES (#7), UBL 2.1 e-Factura XML (#4), and RFC 9562 UUIDv7 Idempotency (#18).

## Output

Returns a SHA-256 hash of the input payload or file, an HMAC-based timestamp seal binding the hash to the current moment, and metadata such as the timestamp used — forming a verifiable, tamper-evident audit record proving the data's content and existence at that point in time.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "payload": {
   "type": "object"
  },
  "fileBase64": {
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/sha-256-hash-hmac-timestamp-audit-seal-2fd1f653/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.ibancheck.co.uk](https://www.zero.xyz/host/api.ibancheck.co.uk/llms.txt)