COMPROMISING ELECTROMAGNETIC EMANATIONS OF WIRED KEYBOARDS
Martin Vuagnoux and Sylvain Pasini
Computer keyboards are often used to transmit sensitive information such
as username/password (e.g. to log into computers, to do e-banking money
transfer, etc.). A vulnerability on these devices will definitely kill
the security of any computer or ATM.
Wired keyboards emit electromagnetic waves, because they contain
eletronic components. These eletromagnetic radiation could reveal
sensitive information such as keystrokes. Although Kuhn already tagged
keyboards as risky, we did not find any experiment or evidence proving
or refuting the practical feasibility to remotely eavesdrop keystrokes,
especially on modern keyboards.
To determine if wired keyboards generate compromising emanations, we
measured the electromagnetic radiations emitted when keys are pressed.
To analyze compromising radiations, we generally use a receiver tuned on
a specific frequency. However, this method may not be optimal: the
signal does not contain the maximal entropy since a significant amount
of information is lost.
Our approach was to acquire the signal directly from the antenna and to
work on the whole captured electromagnetic spectrum.
We found 4 different ways (including the Kuhn attack) to fully or
partially recover keystrokes from wired keyboards at a distance up to 20
meters, even through walls. We tested 11 different wired keyboard models
bought between 2001 and 2008 (PS/2, USB and laptop). They are all
vulnerable to at least one of our 4 attacks.
We conclude that wired computer keyboards sold in the stores generate
compromising emanations (mainly because of the cost pressures in the
design). Hence they are not safe to transmit sensitive information. No
doubt that our attacks can be significantly improved, since we used
relatively inexpensive equipments.
More information on these attacks will be published soon, the paper is
currently in a peer review process for a conference.
Security and Cryptography Laboratory (LASEC) der Eidgenössischen Technischen Hochschule LausanneWeb - Seite : http://lasecwww.epfl.ch/keyboard/ aus rechtlichen Gründen erfolgt keine Verlinkung !