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Halowerk IoT Device HMAC-SHA256 Authentication
x402
Halowerk IoT Device HMAC-SHA256 Authentication is a paid API for AI agents from iot.halowerk.com, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-15).
Canonicalizes device_id, nonce, and message, then computes or verifies an HMAC-SHA256 authentication tag using caller-supplied ephemeral key material for IoT device challenge-response flows.
Price / call$0.002
Success—
StatusUnknown
How this service works
Canonicalizes device_id, nonce and message, computes an HMAC-SHA256 tag with caller-supplied ephemeral key material, and optionally compares a claimed tag in constant time. It does not provision devices, store keys or replace asymmetric device identity; do not submit long-lived production secrets.
Output
Returns the computed HMAC-SHA256 tag as a 64-character hex string over the canonicalized (device_id, nonce, message) tuple. If claimed_tag_hex is provided, also returns a boolean constant-time comparison result indicating whether the claimed tag matches the computed tag. Does not store keys, provision devices, or issue persistent credentials.
Example use cases
IoT gateway device challenge verification
“I need to verify that sensor device 'edge-node-007' produced a valid HMAC-SHA256 tag for the challenge nonce 'b7e2a943f1c08d56' and message 'check-in-ok'. Use ephemeral key 'ek_sess_Kp2mVxNqRjLz9tYw' and compare against the claimed tag the device sent back.”
Firmware command authorization tag
“Generate an HMAC-SHA256 tag to authorize a reboot command for device 'thermostat-fl3-unit9' — use nonce 'd4c8b1e5a2f70936', message 'cmd:reboot:priority=high', and ephemeral key 'ek_cmd_3Wn7hBvXqPsLm2Tz'.”
Agent-side challenge-response during device onboarding
“I'm onboarding a new IoT device with id 'door-lock-b29' and I need to produce a challenge-response tag — nonce is 'f1a3d8c2e5b04796', the challenge message is 'onboard-handshake-v2', and the ephemeral session key is 'ek_onb_Yt6rJmKpVcNx8Qw2'.”
Technical details
Endpoint
POSThttps://iot.halowerk.com/v1/device-authWhen to prefer
Choose this endpoint when you need a stateless, server-side HMAC-SHA256 computation or constant-time tag verification for IoT device challenge-response flows without managing your own crypto library. It is best suited for ephemeral session authentication where you supply short-lived key material per session — not for long-lived production secrets, asymmetric identity, or device provisioning. Prefer this over rolling your own HMAC when you need a consistent canonicalization scheme across heterogeneous IoT devices.
Side effects
- nonce shorter than 8 characters or longer than 256 characters returns a validation error
- ephemeral_key shorter than 16 characters returns a key length error
- claimed_tag_hex not exactly 64 hex characters returns a format validation error
- message exceeding 4096 characters returns a payload size error
- malformed JSON body returns a 400 parse error
- missing required fields (device_id, nonce, message, ephemeral_key) returns a 422 unprocessable entity error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| nonce | string | Fresh caller-generated challenge nonce. |
| message | string | Challenge payload. |
| device_id | string | Stable device identifier. |
| ephemeral_key | string | Ephemeral HMAC key; long-lived production keys must not be sent. |
| claimed_tag_hex | string |
Tags
x402
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