I suppose any of those would work, but I like that idea of lighting it and frantically trying to read it while it's burning. Or maybe a sophisticated read-while

I suppose any of those would work, but I like that idea of lighting it and frantically trying to read it while it's burning. Or maybe a sophisticated read-while-burning machine that continuously burned that page you had just finished along with something to stir the ashes. Foreign intelligence agencies would develop their own discrete sniffer machines to detect faint traces of soot on people to identify potential intelligence personnel. Counter-intelligence would work on psyops campaigns to promote the health benefits of soot & encourage people to use new deodorants and other body grooming products laced with soot to throw them off soot sniffers. The most advanced burn-while-reading devices would have intricate ventilation and ash-isolation chambers with furnaces that burn hot enough to vaporize the ash to the sub-micron level. Portable versions would occasionally malfunction and spontaneously combust the bearer, fueling that particular subset of the tinfoil hat community. It would be an entire soot-based intelligence community arms race, hilariously ridiculous and immensely fascinating.