And what's your defence against torture for literally any other class of asset?

Overseas real estate and other holdings was generally immune to that - in some cases you wouldn't even be able to hand it over to the occupying gov't if you wanted to (since the country with the wealth was hostile to that occupying gov't), in other cases property seized that way was returned through legal means, again through the judiciary of the country where the assets reside, as any contract or transfer under duress is illegitimate and the transfer is reversible.

It being in the vault or at least on an audit trail of some other institution who can later vouch about who seized it, as court evidence.

I doubt that'd work during a war. The best you can hope for is that your country wins and you can collect reparations.

Focus on getting your ass out of there and forget about your assets. Value of an asset to you is zero if you're dead.

That applies to any property and/or secrets hidden away, cryptocurrency or not. Smashing your kneecaps with a wrench until you start singing will work just as well no matter if you have stashed some gold away or if you've memorized a private key.

They would have to know you have crypto assets first. Easy to hide that bit of information.

You can memorize a second seed which holds a small amount for plausible deniability.

- Where are your millions?

- Take this Bitcoin wallet with 10 Bitcoins, please!

- Ok, but where are your millions?