# HMAC-RIPEMD160-Base64 Signing

> HMAC-RIPEMD160-Base64 Signing is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-02).

Computes an HMAC-RIPEMD160 digest of input text using a caller-supplied key and returns it as a base64-encoded string.

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/hmac-ripemd160-base64?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hmac-ripemd160-base64-signing-64357c6e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_XfjoLKGqpGR8KcU7Tn5gl

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-ripemd160-base64-signing-64357c6e -d '<json body>'
```

Example prompt: Compute the HMAC-RIPEMD160 of the text 'Hello, world!' using the key 'my-secret-key' and give me the result as a base64 string.

## When to prefer this

Choose this endpoint when you specifically need the RIPEMD160 algorithm (rather than SHA-256 or SHA-512) for HMAC computation, particularly for compatibility with legacy systems, Bitcoin-ecosystem tooling, or protocols that mandate RIPEMD160 keyed hashing. It is ideal when you need the output in base64 format without additional transformation steps. Use the free sandbox endpoint (/v1/sandbox/hmac-ripemd160-base64) for testing before committing to the paid version.

## Known failure modes

- Empty or missing 'key' field returns a validation error
- Empty or missing 'text' field returns a validation error
- 'key' exceeding 512 characters is rejected
- 'text' exceeding 100,000 characters is rejected
- Payment of $0.003 USDC not provided returns HTTP 402
- Malformed JSON body returns a 400 error

## How this service works

Call when an agent needs an HMAC-ripemd160 of text with a caller-supplied key, encoded as base64. Exact $0.003 USDC. Prefer unpaid POST /v1/sandbox/hmac-ripemd160-base64 first.

## Output

Returns a base64-encoded HMAC-RIPEMD160 digest string computed from the provided text and key. The result is a compact, URL-safe-friendly representation of the keyed hash suitable for use as a signature, checksum, or authentication token.

## 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-ripemd160-base64-signing-64357c6e/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)