WASM で X Chat の UI アプリを構築し、秘密鍵をブラウザーの外に出さない

npm install @xdevplatform/chat-xdk
npm install juicebox-sdk   # required for setup() / unlock() secure key backup

import { createChat } from '@xdevplatform/chat-xdk';

// 1) Create once per page load (client component / browser only)
const chat = await createChat({
  juiceboxConfig: JSON.stringify(record.juicebox_config), // from GET public keys for the user
  getAuthToken: async (realmId) => {
    // Your backend mints a Juicebox realm token for this user + key version.
    // Do not send the user's PIN here—only realm auth for secure key backup.
    const res = await fetch(`/api/juicebox/token?realm=${encodeURIComponent(realmId)}`);
    if (!res.ok) throw new Error('Juicebox token fetch failed');
    return res.text();
  },
});

// 2) First-time identity: generate → register public keys with X → backup with PIN
// const payload = chat.generateKeypairs();
// await registerPublicKeysWithX(payload);  // POST /2/users/:id/public_keys
// await chat.setup(pin);                   // PIN never leaves the browser

// 3) Returning session: recover keys with PIN (once)
await chat.unlock(pin);
chat.setIdentity(userId, signingKeyVersion);
chat.setCacheKeys(true);
// Fetch participants' public keys from X, then:
chat.setSigningKeys(signingKeys);

// 4) Use for the whole SPA session—no more PIN prompts
const result = chat.decryptEvents(rawEvents);
const sendBody = chat.encryptMessage({ conversationId, text: 'Hello' });
// POST sendBody to your backend or X Chat send-message endpoint

// 5) On logout or "lock chat"
chat.lock(); // clears key material from the WASM instance
// chat.free(); // if you will not reuse this instance