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HMAC Signature Computation
x402
HMAC Signature Computation is a paid API for AI agents from hash.openverbs.com, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).
Computes a keyed HMAC (Hash-based Message Authentication Code) over arbitrary data using a shared secret key, supporting SHA-2, SHA-3, BLAKE2, and legacy digest algorithms.
Price / call$0.002
Success—
StatusUnknown
How this service works
Compute a keyed HMAC of some data with a secret key — the standard way to sign and verify webhooks (Stripe, GitHub, etc.) and API requests. Data and key may each be utf8/hex/base64/base64url; the tag is returned as hex/base64/base64url.
Output
Returns the HMAC authentication tag as a string in the requested output encoding (hex by default, or base64/base64url). The tag can be directly compared to an expected signature to verify authenticity, or attached to an outbound request as a signature header.
Example use cases
Verify incoming Stripe webhook
“Sign the raw Stripe webhook body 'amount=1000¤cy=usd&event=charge.succeeded' with my secret 'whsec_abc123' using HMAC-SHA256 and return the hex digest so I can compare it to the Stripe-Signature header.”
Authenticate GitHub webhook delivery
“Compute a GitHub-style HMAC-SHA256 signature of my webhook payload 'ref=refs/heads/main&pusher=alice' using the secret 'github_secret_xyz' encoded as UTF-8 and give me the result in hex.”
Sign outbound API requests with HMAC-SHA512
“Generate an HMAC-SHA512 tag for my API request body 'action=transfer&amount=500' using the base64-encoded key 'c2VjcmV0a2V5MTIz' — decode the key from base64 — and return the signature as base64url.”
Technical details
Endpoint
POSThttps://hash.openverbs.com/v1/hmacWhen to prefer
Choose this endpoint when you need a keyed HMAC rather than a plain cryptographic hash — specifically for webhook signature verification (Stripe, GitHub, Shopify, etc.), API request authentication, or any scenario requiring a shared-secret MAC. Prefer this over a plain hash endpoint whenever message authenticity (not just integrity) is required. Use the sibling plain-hash endpoint when no key/secret is involved.
Side effects
- Invalid or unsupported algorithm name returns a 400 error
- Data or key exceeding size limits (5 MB data, 16 KB key) may be rejected
- Mismatched encoding specification (e.g. non-hex string declared as hex) causes a decoding error
- Missing required fields (data, key, algorithm) returns a validation error
- Payment failure or insufficient USDC balance blocks the request with a 402 response
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object |
Tags
x402
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