Function encrypt

packages/shared/crypto.ts:15–44

(
  compressedData: string
)

 * - key: base64url-encoded 256-bit key for the URL fragment
 */
export async function encrypt(
  compressedData: string
): Promise<{ ciphertext: string; key: string }> {
  const cryptoKey = await crypto.subtle.generateKey(
    { name: 'AES-GCM', length: 256 },
    true,
    ['encrypt']
  );

  const iv = crypto.getRandomValues(new Uint8Array(12));
  const plaintext = new TextEncoder().encode(compressedData);

  const encrypted = await crypto.subtle.encrypt(
    { name: 'AES-GCM', iv },
    cryptoKey,
    plaintext
  );

  // Prepend IV to ciphertext (IV || ciphertext+tag)
  const combined = new Uint8Array(iv.length + encrypted.byteLength);
  combined.set(iv, 0);
  combined.set(new Uint8Array(encrypted), iv.length);

  const rawKey = await crypto.subtle.exportKey('raw', cryptoKey);

  return {
    ciphertext: bytesToBase64url(combined),
    key: bytesToBase64url(new Uint8Array(rawKey)),
  };
}

/**
 * Decrypt a ciphertext string using a base64url-encoded AES-256-GCM key.