There are a plethora of full disk encryption tools. Linux has dm-crypt, Windows has BitLocker, iOS and Android have it. I assume there's a way to enable full disk encryption in OSX but I'm not familiar with the ecosystem.
They can force you to unlock/provide password to your devices if they have probable cause that there is evidence of a crime on the disk. Typically this is because someone looked over a shoulder and saw child porn on the screen. I'm not aware of anyone being forced to provide passwords or keys in any other circumstance, but I'm not an expert.
Encrypt your data, keep your devices off. Do this even if you have "nothing to hide".
They can force you to unlock/provide password to your devices if they have probable cause that there is evidence of a crime on the disk. Typically this is because someone looked over a shoulder and saw child porn on the screen. I'm not aware of anyone being forced to provide passwords or keys in any other circumstance, but I'm not an expert.
Encrypt your data, keep your devices off. Do this even if you have "nothing to hide".