Create interface according to spec

src/utils.ts

@@ -0,0 +1,21 @@
+import { x25519 } from 'bcrypto';
+import * as crypto from 'libp2p-crypto';
+
+import { KeyPair } from "./xx";
+import { bytes } from "./types/basic";
+
+export async function generateKeypair() : Promise<KeyPair> {
+  const privateKey = x25519.privateKeyGenerate();
+  const publicKey = x25519.publicKeyCreate(privateKey);
+
+  return {
+    publicKey,
+    privateKey,
+  }
+}
+
+export async function signPayload(privateKey: bytes, payload: bytes) {
+  const Ed25519PrivateKey = crypto.keys.supportedKeys.ed25519.Ed25519PrivateKey;
+  // const ed25519 = Ed25519PrivateKey(privateKey, "need-to-get-public-key");
+  // return ed25519.sign(privateKey, payload);
+}