From the 'obvious wear' or 'tracking substance added' risks mentioned, it also seems you should, after entering the proper code, touch every other number redundantly as well.
I suppose with 10 transparent markers that are distinguishable under detailed inspection (such as fluorescing to different colors under UV light), you could even work out the right order on the first try: "traces of orange have transferred to 3 other keys, so the orange key was pressed first; traces of green to 2 other... (etc.)"
I wonder whether any of the FLIR imagers that are currently commercially available and reasonably portable are sensitive enough to make this work. Any links?
Comments
From the 'obvious wear' or 'tracking substance added' risks mentioned, it also seems you should, after entering the proper code, touch every other number redundantly as well.
I suppose with 10 transparent markers that are distinguishable under detailed inspection (such as fluorescing to different colors under UV light), you could even work out the right order on the first try: "traces of orange have transferred to 3 other keys, so the orange key was pressed first; traces of green to 2 other... (etc.)"
An even more sinister approach would be to use an infrared meter a couple of seconds after someone just touched the keypad.
I wonder whether any of the FLIR imagers that are currently commercially available and reasonably portable are sensitive enough to make this work. Any links?