[Resource Topic] 2003/217: Chemical Combinatorial Attacks on Keyboards

Welcome to the resource topic for 2003/217

Chemical Combinatorial Attacks on Keyboards

Authors: Eric Brier, David Naccache, Pascal Paillier


This paper presents a new attack on keyboards.

The attack consists in depositing on each keyboard key a small
ionic salt quantity ({\sl e.g.} some NaCl on key 0, some KCl on
key 1, LiCl on key 2, SrCl$_2$ on key 3, BaCl$_2$ on key 4,
CaCl$_2$ on key 5…). As the user enters his PIN, salts get mixed
and leave the keyboard in a state that leaks secret information.
Nicely enough, evaluating the entropy loss due to the chemical
trace turns out to be a very interesting combinatorial exercise.

Under the assumption that mass spectroscopic analysis can reveal with accuracy
the mixture of chemical compounds
generated by the user, we show that, for moderate-size
decimal PINs, the attack would generally disclose the PIN.

The attack may apply to door PIN codes, phone numbers dialed from
a hotel rooms, computer keyboards or even ATMs.

While we did not implement the chemical part of the attack, a number of mass spectrometry
specialists confirmed to the authors its feasibility.

ePrint: https://eprint.iacr.org/2003/217

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