message: Megolm export: Increase to 500000 PBKDF rounds
  This takes 370ms on my machine (100000 only took 100ms).
diff: @@ -102,7 +102,7 @@ export function decryptMegolmKeyFile(data, password) {
  */
  export function encryptMegolmKeyFile(data, password, options) {
  options = options || {};
  - const kdf_rounds = options.kdf_rounds || 100000;
  + const kdf_rounds = options.kdf_rounds || 500000;
  const salt = new Uint8Array(16);
  window.crypto.getRandomValues(salt);
  @@ -164,6 +164,7 @@ export function encryptMegolmKeyFile(data, password, options) {
  * @return {Promise<[CryptoKey, CryptoKey]>} promise for [aes key, hmac key]
  */
  function deriveKeys(salt, iterations, password) {
  + const start = new Date();
  return subtleCrypto.importKey(
  'raw',
  new TextEncoder().encode(password),
  @@ -182,6 +183,9 @@ function deriveKeys(salt, iterations, password) {
  512
  );
  }).then((keybits) => {
  + const now = new Date();
  + console.log("E2e import/export: deriveKeys took " + (now - start) + "ms");
  +
  const aes_key = keybits.slice(0, 32);
  const hmac_key = keybits.slice(32);
  