FastX402 Lab HMAC Sign & Verify

x402

FastX402 Lab HMAC Sign & Verify is a paid API for AI agents from fastx402.tools, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-17).

Computes HMAC-SHA256 or HMAC-SHA512 of a message with a secret key, and optionally verifies it against a provided signature

Price / call$0.002

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StatusUnknown

How this service works

146 pay-per-call tools for AI agents, from $0.001 per request in USDC on Base or Solana with x402. No account, no API key.

Output

Returns a JSON object containing the HMAC digest in both hex and base64 formats, the algorithm used (sha256 or sha512), and a 'matches' field (true/false/null) indicating whether the optional provided signature matched the computed HMAC.

Example use cases

Verify incoming Stripe webhook

“I just got a Stripe webhook and need to verify it's legit — the payload is '{"type":"payment_intent.succeeded"}', my webhook secret is 'whsec_abc123', and Stripe sent the signature 'sha256=aef34...'. Can you check if it matches using HMAC-SHA256?”

Generate HMAC signature for outgoing request

“I need to sign the message 'order_id=42&amount=99.99&currency=USD' with the shared secret 'topsecret' using HMAC-SHA256 so I can attach it to my outgoing API call — give me the hex digest.”

Verify GitHub webhook payload

“GitHub sent a webhook with payload 'refs/heads/main pushed' and the header X-Hub-Signature-256 is 'sha256=deadbeef...'. My webhook secret is 'ghsecret99'. Can you verify with HMAC-SHA256 whether the signature is valid?”

Technical details

Endpoint

GEThttps://fastx402.tools/hmac-sign?utm_source=zero.xyz

When to prefer

Choose this endpoint when you need a quick, stateless HMAC computation or webhook signature verification without setting up local crypto libraries. Especially useful for verifying Stripe, GitHub, or Shopify webhooks in an agentic pipeline where inputs are not stored and pay-per-call cost is acceptable.

Side effects

Missing required 'message' or 'secret' query parameters returns an error
Invalid algorithm value (not sha256 or sha512) may return an error or default to sha256
Malformed signature format may cause 'matches' to return null rather than true/false
Empty message or secret strings may produce unexpected HMAC values

Input

Schema · Request body

Field	Type	Description
inputrequired	object
output	object

Output

Schema · Response

{
  "type": "json",
  "example": {
    "hex": "b85236760a6447cd065efe2b7bd10554c3744eff60cc53dfa47a639c5fd1e22c",
    "base64": "uFI2dgpkR80GXv4re9EFVMN0Tv9gzFPfpHpjnF/R4iw=",
    "matches": null,
    "algorithm": "sha256"
  }
}

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