In message <[EMAIL PROTECTED]>, John Levine writes: >>http://www.fas.org/sgp/othergov/dod/nsa-redact.pdf >> >>One wonders how long it will be till someone finds an error... > >Even if it's right, it's so complicated that it seems rather >optimistic to expect people to follow it correctly every time.
I agree. It's also very dependent on the exact options that Microsoft and Adobe have currently implemented. Minor changes could screw this up completely. > >I don't claim to be a big security guru, but if I were planning to >distribute a redacted PDF document, I'd render it to a bitmap, then >turn the bitmap back into a PDF and ship that, a digital version of >printing it out and scanning it back in. On Unixish systems, one can >do that in about five minutes with freeware tools like ghostscript and >xpdf. That's more or less what they did when they declassified Skipjack, though they may have used a real printer and scanner instead. Some people laughed at NSA's technical ineptitude -- didn't they know how to print to PDF directly? Others realized that NSA understood the problem at a much deeper level. --Steven M. Bellovin, http://www.cs.columbia.edu/~smb --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]