Today’s invention is a pair of nail clippers with a serrated edge.
The positions of the serrations can be selected by the user so that a subtle pattern can be created in anyone’s fingernails.
I estimate that it would be possible to have about five such notches cut into each nail without these being obvious to a casual observer.
The result would be a code, representing 2^(10*5) different messages -which would allow identification of an individual.
Such a code, whilst crude, could be carried by anyone -perhaps even without their knowledge.
It would also have a clearly limited lifetime and might, if necessary, be destroyed in a few, nailbiting seconds.