> For the complete documentation index, see [llms.txt](https://vampauth.gitbook.io/vampauth-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://vampauth.gitbook.io/vampauth-docs/development/key-check.md).

# Node.js key-check client

Save as check-key.mjs and run with Node.js 18 or later. Set VAMPAUTH\_PROJECT\_ID, VAMPAUTH\_AUTH\_SECRET, VAMPAUTH\_KEY, and APP\_DEVICE\_ID in your backend environment.

This is a real validation call: success activates a pending first-use key. Use management lookup for stock inspection.

```javascript
import { createHash, createHmac, randomBytes, timingSafeEqual } from "node:crypto";

const projectId = process.env.VAMPAUTH_PROJECT_ID;
const secret = process.env.VAMPAUTH_AUTH_SECRET;
const key = process.env.VAMPAUTH_KEY;
const deviceId = process.env.APP_DEVICE_ID;

if (!projectId || !secret || !key || !deviceId) {
  throw new Error("Set the project ID, auth secret, key, and device ID.");
}

const hmac = (parts) => createHmac("sha1", secret)
  .update(parts.join("|"), "utf8")
  .digest("hex");

async function checkKey() {
  const hwid = createHash("sha256").update(deviceId, "utf8").digest("hex");
  const nonce = randomBytes(16).toString("hex");
  const response = await fetch("https://vampauth.com/api/v1/key/check", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    signal: AbortSignal.timeout(10_000),
    body: JSON.stringify({ project_id: projectId, key, hwid, nonce,
      signature: hmac([nonce, key, hwid]) }),
  });
  const data = await response.json();
  if (!response.ok) throw new Error(data?.error || "HTTP " + response.status);
  if (!data || data.status !== "valid" || data.project_id !== projectId ||
      data.nonce_echo !== nonce || !/^[0-9a-f]{40}$/.test(data.signature)) {
    throw new Error("Invalid key-check response.");
  }
  const expiryMs = data.expires_at === null ? null :
    (typeof data.expires_at === "string" ? Date.parse(data.expires_at) : NaN);
  if (expiryMs !== null && !Number.isFinite(expiryMs)) {
    throw new Error("Invalid expiry in key-check response.");
  }
  const expirySeconds = expiryMs === null ? 0 : Math.floor(expiryMs / 1000);
  const expected = Buffer.from(hmac([nonce, data.status, expirySeconds, projectId]), "hex");
  const received = Buffer.from(data.signature, "hex");
  if (!timingSafeEqual(expected, received)) throw new Error("Response signature did not match.");
  if (expiryMs !== null && expiryMs <= Date.now()) throw new Error("Key expired.");
  return data;
}

try {
  const result = await checkKey();
  console.log("Key accepted. Expires:", result.expires_at ?? "never");
  // Continue with the part of your app that needs access.
} catch (error) {
  console.error("Key check failed:", error.message);
  process.exitCode = 1;
}
```

The request signature uses nonce, key, and HWID. The response signature uses nonce, status, expiry in whole seconds, and the exact project ID sent. Don't interchange those messages or accept a response just because its HTTP status is 200.

## Next steps

* [Standalone key check](/vampauth-docs/api-reference/key-check.md)
* [Keys and expiry](/vampauth-docs/features/keys-and-expiry.md)


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