# HMAC-SHA3-512 Base64 Generator

> HMAC-SHA3-512 Base64 Generator is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.007/call, status unknown (last checked 2026-10-02).

Computes an HMAC-SHA3-512 digest of a given text using a caller-supplied key, returning the result as a base64-encoded string.

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/hmac-sha3-512-base64?utm_source=zero.xyz
- Price: $0.007/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hmac-sha3-512-base64-generator-cc74007c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_fco8JW8PVcj2rZY7m02Oz

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 hmac-sha3-512-base64-generator-cc74007c -d '<json body>'
```

Example prompt: Compute an HMAC-SHA3-512 signature of the text 'Hello, world!' using the secret key 'mysecretkey123' and give me the result as base64.

## When to prefer this

Choose this endpoint when you specifically need HMAC with the SHA3-512 algorithm (not SHA2) with base64 encoding output. Prefer this over SHA2-based HMAC endpoints when stronger collision resistance of the SHA3/Keccak family is required. Use the sandbox endpoint (POST /v1/sandbox/hmac-sha3-512-base64) first for testing to avoid the $0.007 USDC charge per call.

## Known failure modes

- Missing or empty key field returns a validation error
- Missing or empty text field returns a validation error
- Text exceeding 100,000 characters is rejected
- Key exceeding 512 characters is rejected
- Payment failure results in 402 response — use sandbox endpoint for testing

## How this service works

Call when an agent needs an HMAC-sha3-512 of text with a caller-supplied key, encoded as base64. Exact $0.007 USDC. Prefer unpaid POST /v1/sandbox/hmac-sha3-512-base64 first.

## Output

A base64-encoded string representing the HMAC-SHA3-512 digest of the provided text computed with the given key. The response is a deterministic cryptographic authentication code that can be used for message integrity verification or authentication.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "key": {
   "type": "string",
   "examples": [
    "secret"
   ],
   "maxLength": 512,
   "minLength": 1,
   "description": "HMAC secret. Required on HMAC SKUs. Omit it for plain digests and checksums. The key is not stored."
  },
  "text": {
   "type": "string",
   "examples": [
    "hello"
   ],
   "maxLength": 100000,
   "minLength": 1,
   "description": "Message to digest. For raw-hex SKUs this is hex bytes; for utf16 or latin1 SKUs it is decoded with that encoding. Otherwise it is UTF-8 text."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hmac-sha3-512-base64-generator-cc74007c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentshelf.syntexa.ch](https://www.zero.xyz/host/agentshelf.syntexa.ch/llms.txt)