> For the complete documentation index, see [llms.txt](https://k4k3ru.gitbook.io/k4k3ru-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://k4k3ru.gitbook.io/k4k3ru-docs/api/authentication/sign-request-with-typescript.md).

# Sign a Request with TypeScript

Build an authenticated K4K3RU JSON-RPC request with TypeScript on Node.js. Node.js handles HMAC-SHA256, and TweetNaCl signs with the 64-byte Ed25519 private key issued by K4K3RU.

## Prerequisites

* Node.js 20 or later.
* An API credential created with `hmac-sha256` or `ed25519`.
* `K4K3RU_API_KEY`, `K4K3RU_SECRET_KEY`, and `K4K3RU_SIGNATURE_ALGORITHM` set in your environment.

Create a project and install the example dependencies:

```bash
npm install tweetnacl
npm install --save-dev typescript tsx @types/node
```

## Example

Save this program as `sign-request.ts`:

```typescript
import { createHmac, randomBytes } from "node:crypto";
import nacl from "tweetnacl";

type JsonValue = null | boolean | number | string | JsonValue[] | { [key: string]: JsonValue };

function requireEnv(name: string): string {
  const value = process.env[name];
  if (!value) throw new Error(`set ${name}`);
  return value;
}

function canonicalize(value: JsonValue): JsonValue {
  if (Array.isArray(value)) return value.map(canonicalize);
  if (value !== null && typeof value === "object") {
    return Object.fromEntries(
      Object.keys(value)
        .sort()
        .map((key) => [key, canonicalize(value[key])]),
    );
  }
  return value;
}

function sign(algorithm: string, secret: Buffer, payload: Buffer): Buffer {
  if (algorithm === "hmac-sha256") {
    return createHmac("sha256", secret).update(payload).digest();
  }
  if (algorithm === "ed25519") {
    if (secret.length !== nacl.sign.secretKeyLength) {
      throw new Error(`invalid Ed25519 private key length: ${secret.length}`);
    }
    return Buffer.from(nacl.sign.detached(payload, secret));
  }
  throw new Error(`unsupported signature algorithm: ${algorithm}`);
}

const apiKey = requireEnv("K4K3RU_API_KEY");
const secret = Buffer.from(requireEnv("K4K3RU_SECRET_KEY"), "base64url");
const algorithm = requireEnv("K4K3RU_SIGNATURE_ALGORITHM");
const method = "PaymentOnchain.CreateIntent";
const params: JsonValue = { productName: "usdc-base-mainnet-1" };
const timestamp = Math.floor(Date.now() / 1000);
const nonce = randomBytes(16).toString("base64url");
const canonicalParams = JSON.stringify(canonicalize(params));
const payload = Buffer.from(`${method}\n${timestamp}\n${nonce}\n${canonicalParams}`, "utf8");
const signature = sign(algorithm, secret, payload).toString("base64url");

console.log(JSON.stringify({
  id: "1",
  method,
  params,
  auth: { apiKey, timestamp, nonce, signature },
}, null, 2));
```

Run it with:

```bash
npx tsx sign-request.ts
```

The program prints a request body that you can send to `https://api.k4k3ru.com/` with `Content-Type: application/json`. Build the payload and request from the same `params` object so their values cannot diverge.

## Next Steps

See [API Request Authentication](/k4k3ru-docs/api/authentication.md) for canonicalization, freshness, replay-protection, and troubleshooting requirements.


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