title_body: How much entropy does BIP39 have? How much entropy does BIP39 have?
  How long would brute forcing take?
  Can a 2nd factor be included on a wallet, to lock, unlock it?
upvoted_answer: 128 bit for 11 seed word and 256 for 27 seed word
  for 128 bit 1.02 x 10^18 years.