Universal Unsearchability

The principle that it’s impossible to search through the universe to determine whether some piece of information exists somewhere.

You cannot know if someone has seen your passwords or private keys. You cannot verify that data has truly been deleted; only that it’s been made harder to find. The bits may persist on a disk until overwritten; copies may exist on backup tapes, in memory dumps, in someone else’s notes.

This is a fundamental limit on privacy and data ownership: encryption can make data unreadable, but cannot prove that no copy exists elsewhere.