user533: 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?

user607: 128 bit for 11 seed word and 256 for 27 seed word
for 128 bit 1.02 x 10^18 years.

user565: I'd take a look at this answer
It seems a very well resourced attacker would be able to find a used private key for 128bit seed.
This would be an attack on all keys in the network, not yours specifically.
For 256bit seed, it should be infeasible.

533: <p>How much entropy does BIP39 have?</p>
<p>How long would brute forcing take?</p>
<p>Can a 2nd factor be included on a wallet, to lock, unlock it?</p>
 607: <p>128 bit for 11 seed word and 256 for 27 seed word
for 128 bit 1.02 x 10^18 years.</p>
 565: <p>I'd take a look at this <a href="https://crypto.stackexchange.com/a/86803/36633">answer</a></p>
<p>It seems a very well resourced attacker would be able to find a used private key for 128bit seed.
This would be an attack on all keys in the network, not yours specifically.
For 256bit seed, it should be infeasible.</p>
