European researchers have figurd out a way to figure out what the blacked-out words are in redacted government documents, by calculating pixel widths in the blacked out spots.
The researchers showed their software at the conference, called Eurocrypt, by analyzing a presidential briefing memorandum released in April to the commission investigating the Sept. 11 attacks. After analyzing the document, they said they had high confidence the word “Egyptian” had been blacked out in a passage describing the source of an intelligence report stating that Osama Bin Ladin was planning an attack in the United States.
The researchers, David Naccache, the director of an information security lab for Gemplus, a Luxembourg-based maker of banking and security cards, and Claire Whelan, a computer science graduate student at Dublin City University in Ireland, also applied the technique to a confidential Defense Department memorandum on Iraqi military use of Hughes helicopters.
They said that although the name of a country had been blacked out in that memorandum, their software showed that it was highly likely the document named South Korea as having helped the Iraqis.
It’s only possible because of recent US government moves toward standardizing on proportional fonts.
I guess it’s a clever thing to have figured out, though I suppose it means the government will go to greater efforts in redaction — or in finding alternative ways of releasing FOIA info — or even use it as an excuse not to release redacted source documents.