International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Chemical Combinatorial Attacks on Keyboards

Eric Brier
David Naccache
Pascal Paillier
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Abstract: This paper presents a new attack on keyboards. \smallskip 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. \smallskip 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. \smallskip The attack may apply to door PIN codes, phone numbers dialed from a hotel rooms, computer keyboards or even ATMs. \ss While we did not implement the chemical part of the attack, a number of mass spectrometry specialists confirmed to the authors its feasibility.
  title={Chemical Combinatorial Attacks on Keyboards},
  booktitle={IACR Eprint archive},
  keywords={implementation /},
  note={chemistry attack keyboard combinatorics entropy 12334 received 9 Oct 2003},
  author={Eric Brier and David Naccache and Pascal Paillier},