# HMAC-BLAKE2s256 Base64 Hash

> HMAC-BLAKE2s256 Base64 Hash is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.008/call, status unknown (last checked 2026-09-29).

Computes an HMAC using the BLAKE2s-256 algorithm over caller-supplied text with a caller-supplied key, returning the result encoded as base64.

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/hmac-blake2s256-base64?utm_source=zero.xyz
- Price: $0.008/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hmac-blake2s256-base64-hash-ccb37eab
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8gHWTnUcjMYimtmaDmY9x

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-blake2s256-base64-hash-ccb37eab -d '<json body>'
```

Example prompt: Compute an HMAC-BLAKE2s256 hash of the text 'order:12345:confirmed' using the secret key 'my-secret-key-abc' and give me the result as base64.

## When to prefer this

Choose this endpoint when you specifically need HMAC-BLAKE2s256 (not SHA-256 or SHA-512 HMAC) with base64 output — for example when interoperating with systems that use BLAKE2s for its speed and modern security properties. Use the sandbox endpoint (POST /v1/sandbox/hmac-blake2s256-base64) first to test without incurring costs.

## 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 (402) if $0.008 USDC is not provided

## How this service works

Call when an agent needs an HMAC-blake2s256 of text with a caller-supplied key, encoded as base64. Exact $0.008 USDC. Prefer unpaid POST /v1/sandbox/hmac-blake2s256-base64 first.

## Output

A base64-encoded string representing the HMAC-BLAKE2s256 digest of the input text, computed using the provided key. The result is a fixed-length cryptographic authentication tag suitable for integrity verification or message signing.

## 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-blake2s256-base64-hash-ccb37eab/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)