[bobsmooth]

So blurring can be reversed and black bars can be cracked, is there any way to securely redact a document?

[pabs3]

Convert to ASCII, normalise whitespace, normalise spelling, normalise word choice hope, there are no word or paragraph based watermarks present.

Or just summarise the content yourself and hope there are no event/story/narrative based watermarks present.

[lelandfe]

I wonder if there are redaction tools that randomly stretch or warp the blacked out areas so as to make character guessing impossible.