@AlcoHoDL
It's always great to read your explanations! My only concern would be if the thief is smart enough to torture a bitcoiner to the point of having him to release the full passphrase. This is so scary to even think.
Thanks. Yes, it's scary as hell, and you're right, it could happen. What you can do to try to circumvent this, is to have not only one, but two, or three, or more, different passphrases.
Your total stash:
100 BTC. <--- I wish!No passphrase (plain seed):
3.7 BTCPassphrase 1:
17.3 BTCPassphrase 2:
79 BTC-- Thief kidnaps you and forces you to reveal your Trezor's PIN.
-- You resist as much as you can, but eventually you reveal the PIN.
-- Thief takes the 3.7 BTC, but suspects you have an additional passphrase.
-- Thief tortures you to reveal it.
-- You endure the torture as much as you can (you must, and be prepared to take a good beating).
-- Eventually, you break down in extreme distress, and you reveal passphrase 1.
-- You repeatedly plead with the thief to let you have a few BTC, even just one.
-- Thief takes the 17.3 BTC, and notices that 17.3 + 3.7 = 21 BTC.
-- Thief thinks your total stash is the "one in a million" 21 BTC that many HoDLers aim for.
-- If you're lucky, he takes it "all" and lets you go.
-- You are left with a healthy
79 BTC, accessible using passphrase 2.
This is just one strategy that uses common thinking to try to persuade the thief that you have no more coins. Of course, the best thing to do is to try not to get into this situation in the first place. Try not to advertise your stash (obviously), and don't give away even minor hints about how many coins you have. Easier said than done though... Even the mere mention of being involved in Bitcoin, combined with a few major changes in your life (something expensive you've bought, resigning from your job, etc.) would point to a healthy Bitcoin stash. That's why I believe all those tools we have (additional passphrase, plausible deniability, Shamir's Secret Sharing, and others), can help in our attempts to circumvent unfortunate situations like the one you describe.
Bitcoin has made many of us take security matters very seriously, much more seriously than before, when banks and other financial institutions played that role. Bitcoin is cash, and has all the benefits (and drawbacks) of cash. Imagine having $1M in banknotes or gold under your bed. Wouldn't you feel stressed about it? I would. It's the same with Bitcoin, but the fact that it's not made of matter, but of information that can be stored and processed digitally, enables us to use certain tools, such as the ones mentioned earlier, to help protect our coins. "Be a bank" is revolutionary and gives us total control of our finances, but can also be a burden if we're not adequately prepared to take the responsibility and care it requires.
Stay safe, and, when it comes to Bitcoin, apply the Manhattan Project's motto:
http://exploreoakridge.com/who-were-the-calutron-girls-of-oak-ridge/---
Edit: JayJuanGee beat me to it. Thanks Jay.