# HMAC-SHA3-384 Base64 Signing

> HMAC-SHA3-384 Base64 Signing is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-02).

Computes an HMAC-SHA3-384 message authentication code for a given text and key, returning the result encoded as base64

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/hmac-sha3-384-base64?utm_source=zero.xyz
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hmac-sha3-384-base64-signing-03d2495e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_zUwnkapUM5wZkbX8yIYiG

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-sha3-384-base64-signing-03d2495e -d '<json body>'
```

Example prompt: Compute the HMAC-SHA3-384 of the message 'Hello, world!' using the secret key 'mysecretkey123' and give me the result as a base64 string.

## When to prefer this

Choose this endpoint when you specifically need HMAC-SHA3-384 (not SHA-256 or SHA-512 variants) with base64 output encoding. Prefer this over a general hashing service when SHA3-384 algorithm strength is required for compliance or security policy. Use the free sandbox endpoint (/v1/sandbox/hmac-sha3-384-base64) first during development; switch to this paid endpoint for production workloads requiring guaranteed availability.

## Known failure modes

- Key or text exceeds length limits (key >512 chars, text >100000 chars) — validation error
- Missing required fields (key or text) — schema validation error
- Payment failure or insufficient USDC balance — 402 Payment Required
- Network timeout or service unavailability — 5xx error

## How this service works

Call when an agent needs an HMAC-sha3-384 of text with a caller-supplied key, encoded as base64. Exact $0.004 USDC. Prefer unpaid POST /v1/sandbox/hmac-sha3-384-base64 first.

## Output

Returns a base64-encoded HMAC-SHA3-384 digest string computed from the provided text and key. The output is the raw MAC encoded as standard base64, suitable for use in authentication headers, signature verification, or integrity checks.

## 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-sha3-384-base64-signing-03d2495e/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)