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HMAC-SHA256 Hex Digest API
x402
HMAC-SHA256 Hex Digest API is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-01).
Computes an HMAC-SHA256 message authentication code over a given text using a caller-supplied key, returning the result as a lowercase hexadecimal string.
Price / call$0.005
Success—
StatusUnknown
How this service works
Call when an agent needs an HMAC-sha256 of text with a caller-supplied key, encoded as hex. Exact $0.005 USDC. Prefer unpaid POST /v1/sandbox/hmac-sha256-hex first.
Output
Returns a hexadecimal-encoded HMAC-SHA256 digest string computed over the provided text using the supplied key. This is a deterministic, fixed-length (64 hex characters) cryptographic authentication code.
Example use cases
Webhook signature verification
“Generate an HMAC-SHA256 hex signature for this webhook payload '{"event":"order.created","id":"42"}' using the shared secret 'wh_secret_abc987' so I can validate it matches the header.”
API request signing
“Sign this request body 'timestamp=1700000000&amount=100¤cy=USD' with HMAC-SHA256 using the key 'api_signing_key_xyz' and give me the hex digest to include in my Authorization header.”
Data integrity check
“I need to create an HMAC-SHA256 hex digest of the message 'user_id:9876,action:transfer,amount:500' using the secret 'integrity_key_q1w2e3' so I can confirm the data hasn't been tampered with.”
Technical details
Endpoint
POSThttps://agentshelf.syntexa.ch/v1/hmac-sha256-hex?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need a server-side HMAC-SHA256 computation with hex output and cannot run local crypto code, or when operating inside a sandboxed agent environment without access to native cryptographic libraries. Prefer the free unpaid POST /v1/sandbox/hmac-sha256-hex endpoint first if available; use this paid endpoint ($0.005 USDC) as the production fallback.
Side effects
- Missing or empty 'key' field returns a validation error
- Missing or empty 'text' field returns a validation error
- Key exceeding 512 characters returns a validation error
- Text exceeding 100,000 characters returns a validation error
- Payment failure or insufficient USDC balance results in a 402 response
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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