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HMAC-SHA3-256 Hex Digest
x402
HMAC-SHA3-256 Hex Digest 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-SHA3-256 message authentication code for a given text and key, returning the result as a lowercase hex string.
Price / call$0.004
Success—
StatusUnknown
How this service works
Call when an agent needs an HMAC-sha3-256 of text with a caller-supplied key, encoded as hex. Exact $0.004 USDC. Prefer unpaid POST /v1/sandbox/hmac-sha3-256-hex first.
Output
A hex-encoded HMAC-SHA3-256 string (64 lowercase hex characters) computed from the provided text and key, confirming message authenticity and integrity.
Example use cases
API request signing for webhook
“I need to sign this webhook payload 'user.created:{"id":42}' with my secret key 'wh_secret_abc123' using HMAC-SHA3-256 hex so I can include the signature in the header.”
Message integrity verification token
“Generate an HMAC-SHA3-256 hex digest for the message 'order_id=9981&amount=59.99¤cy=USD' using the key 'payment_signing_key_v2' so I can attach it as a tamper-proof checksum.”
Secure configuration file signing
“Compute the HMAC-SHA3-256 in hex for this JSON config string '{"env":"prod","debug":false}' with the key 'cfg-integrity-key-007' so I can validate it hasn't been modified at runtime.”
Technical details
Endpoint
POSThttps://agentshelf.syntexa.ch/v1/hmac-sha3-256-hex?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you specifically need HMAC-SHA3-256 (not HMAC-SHA256 or other variants) with hex-encoded output and have a caller-supplied secret key. Prefer the free sandbox endpoint POST /v1/sandbox/hmac-sha3-256-hex for testing before spending $0.004 USDC per call on this paid version. Use this over generic hashing endpoints when a keyed MAC (not a plain digest) is required for authentication or integrity verification.
Side effects
- Key or text is empty or exceeds length limits (400 Bad Request)
- Text exceeds 100,000 character limit
- Key exceeds 512 character limit
- Insufficient USDC balance for $0.004 payment (402 Payment Required)
- Network timeout or server unavailability (503)
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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