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HMAC-SHA3-256 Base64 Signing
x402
HMAC-SHA3-256 Base64 Signing is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-02).
Computes an HMAC-SHA3-256 message authentication code for a given text using a caller-supplied key and returns the result encoded as base64.
Price / call$0.005
Success—
StatusUnknown
How this service works
Call when an agent needs an HMAC-sha3-256 of text with a caller-supplied key, encoded as base64. Exact $0.005 USDC. Prefer unpaid POST /v1/sandbox/hmac-sha3-256-base64 first.
Output
Returns a base64-encoded HMAC-SHA3-256 digest string computed from the provided text and key. The output is a standard base64 string representing the 256-bit message authentication code.
Example use cases
Webhook payload integrity signing
“I need to sign the webhook payload 'user_created:{"id":42,"email":"alice@example.com"}' with the key 'wh_secret_prod_abc123' using HMAC-SHA3-256 and get the base64 result to include in the X-Signature header.”
API request authentication token
“Generate an HMAC-SHA3-256 base64 signature for the string 'GET:/api/v2/orders:1717200000' using the key 'api_signing_key_xyz' so I can authenticate this API request.”
Data integrity check for stored record
“Compute the HMAC-SHA3-256 of 'transaction:TXN-20240601-8812,amount:250.00,currency:USD' with the key 'integrity_check_key_prod' and return it as base64 so I can store it alongside the record.”
Technical details
Endpoint
POSThttps://agentshelf.syntexa.ch/v1/hmac-sha3-256-base64?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need HMAC-SHA3-256 specifically (not SHA-256, SHA-384, or other HMAC variants) and require the output as standard base64 encoding. Prefer it over the sandbox endpoint when the computation must be performed in a production billing context. Use the sibling SHA-384/base64url endpoint if you need the SHA-384 algorithm or base64url encoding instead of base64.
Side effects
- Empty or missing key (minLength:1 violated) returns a validation error
- Empty or missing text (minLength:1 violated) returns a validation error
- Text exceeding 100,000 characters returns a payload-too-large error
- Key exceeding 512 characters returns a validation error
- Payment of exactly $0.005 USDC required; insufficient funds returns 402
- Network timeout on the paid endpoint — retry with the free sandbox endpoint at /v1/sandbox/hmac-sha3-256-base64
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| key | string | HMAC secret. Required on HMAC SKUs. Omit it for plain digests and checksums. The key is not stored. |
| text | string | 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. |
Tags
x402
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