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S400 Scanner Modified For Finding Hidden Watermarks

Computer {hardware} is through and big compromised out of the field. Whether it’s sloppy manufacturing unit code, or government-installed backdoors, it’s tricky to believe the rest. A perfect instance is that of colour laser printers, nearly all of which position hidden watermarks on revealed pages. It’s a moderately forgotten factor at the present time, however again in 2005, [bunnie] got down to alter a scanner to assist higher symbol and examine those watermarks.

The watermarks in query were investigated through the EFF, and regularly, however now not at all times, include tiny yellow dots imprinted on the web page. They can retailer knowledge such because the title of the pc that revealed the record, in addition to the serial quantity and fashion of the printer used. With this capability baked into the firmware, all prints made on this type of printer are compromised.

The perfect approach to see those watermarks is with blue gentle, which is mirrored through the white paper, however reasons yellow dots to turn up as darkish spots. To make scanning affected paperwork fast and simple, [bunnie] whipped up a linear LED gentle array, putting in it in a spare fit in his scanner’s gentle meeting, subsequent to the inventory white CCFL. Usage is a bit more advanced, with the scanner’s automated calibration getting at a loss for words if the blue LEDs are left on firstly of a scan. Instead, the LEDs should be grew to become off first of all, after which powered up as soon as the calibration is entire.

Results are just right, with the tiny dots made a lot clearer within the take a look at scans [bunnie] carried out. Unfortunately, the watermarking generation has moved on, and it’s most likely that fashionable printers use a number of tactics which might be even tougher to stumble on. By and big, ransom notes are highest made the old school manner – through chopping up some outdated magazines.