Not joking. Is powering down through a cron job the only solution?
 

Let's suppose I (and my accomplices of course) have a recipe to form a government that does not need politicians. Politicians automatically become my most lethal enemies when they become aware of my subversive website (nothing to do with version control like Subversion) and I might have good reasons to fear that, beside killing me after having asked the Chinese and the Russian experts the best way to do it in secret, they can coerce the police and the army and the secret services, even foreign politicians to seize my computers to silence me and my dissident and terrorist beloved friends.
Let's suppose I am using SED SSD with a KEK and a MEK to prevent that as, being the extremist I am, I think my drafts are more important than my own life. But they know that and after killing me despite the protection of my backup-loaded suicide vest, they seize my computers in a way that power remains "on" and all my files are readable to them due to the way self-encrypting drives work.
How can I solve this terrible problem other than as suggested above, with a cron job expecting an answer within a specified time, answer only known by one of those very dangerous dissident and terrorist supporters of governments-without-politicians, so I do not die in vain?

Thank you for your help.

you been smoking something?

if you are really serious about this, explain the issue properly, not as a mr-robot-style short story.

The issue is obviously the fact that authorities (or audacious thieves convincingly disguised as some authority) can seize operational computers and maintain their "power on" status in order to later read files stored on SED SSD (or other SED drive) without having to provide a password and the solution to protect the files in such case appears to have a cron job asking regularly for a password or similar which has to be supplied within a certain time or the cron job turns power off (halt the system). The seized or stolen powered-off computers will then need to be given an unknown "key encryption key" (KEK) or only the useless encrypted data is available if the drive is put into another computer.
Presenting such issue in a conventional way always degenerate into interminable objections by those of the view one should not have anything to hide against those of the view hidding is a right and necessary, hence my scenario. May be others will not share your views.

Please review the Site FAQ for guidance in asking clear and complete questions, which is the standard for asking questions in the technical fora.

Presenting it as you have with only a cloak-and-dagger novel type context, and no useful technical details, is much more likely to generate interminable tertiary discussion. As such your question does not rise to the level of a programming question and makes this thread more suitable for the General forum, where it will be moved.

If you need help with a data security problem, a well framed question in the Security forum would be more appropriate. If you need help with a specific programming problem, a well framed question in the Programming forum is the way to get help.

In the hypothetical scenario you describe, I do not think any sort of software solution would provide security. The only way to approach that problem would be to never power those systems up outside a physically secure environment, and never ever allow them to remain powered up when not attended by a person with complete control of that physical access - not even for a minute.

Good luck!

#1 why do your drives not have thermite self-distruct functions

#2 the only secure computer is in a locked room, under guard, with the guard monitored, on filtered power with no network and limited access based upon security level and need to know.

#3 The more secure option is to not use a computer and obfuscate your traces. We could teach you, but then you would be on our "list". You would not want that.

usage habits:
switch your machine off when you don't use it.
of course that's not all, but usage habits go a long way, wrt that whole privacy/security thingy.