Commonly known contactless chipcards communicate with the coupler
through only one single (magnetic) antenna.
Therefore the unnoticed access to the card's contents from a remote
coupler is not precluded by an intrinsic property: The card holder's
sovereignty over her/his own data is not assured by principle this
way (See an example of this problem here, in German by Stuttgarter Zeitung of
2006-02-03, page 1.).
A more recent one is here by ConsumerReports® of June 2011
(more ...)
or here, in German by DER SPIEGEL of
2012-06-11, page 128 or here, by Los Angeles Times of
2016-12-10, page C3.). A quite straight-forward antidote ist the RFID Blocker envelope like
this. Google knows a lot about them too.
What's new
To overcome this drawback,
ADE's
C2® fashion implements
two spatially separated antennas rather than only
one. Since these two antennas carry two distinctively modulated
signals, a sum/difference matrix within the card can decide whether
the card is located quite close to the coupler or more distant.
As a consequence, the usability of the card ist clearly limited by
the pure geometry of the card - not any more by sheer intensity of
the coupling field. It is assured that such a card can only be
communicated with in a limited coupling environment (say, a bank
terminal), that the coupling mechanism can withhold the card
reliably in case of trouble.
Not the environment governs the access to the card data -
the card itself does:
The reason why
The figure attempts to give an idea of how the effect is
achieved. It shows a cross section availing a plane where all the
centers of both the coupler's antenna pair and the card's antenna
pair are located in at the same time. Here, the coupler's antenna
pair is supposed to be located fixed in space (the upper pair of
short black bars, fed from the generator through two opposite phase
shifters). On the other hand, another pair of short bars represents
the card's antenna pair that is not fixed in space and therefore
depicted at several distinct positions. For the drawing, these
positions are selected as typical for the different situations in
order to prove the principle of operation: The card works in such
positions (green bars), where not only the magnetic flux (the solid
blue circles) penetrates the card as most dense and perpendicular,
but also the
two timing vectors (the straight lines in the tiny circles) in both
of the card's antennas are most perpendicular to each other. The
long blue dash-dotted straight lines are polarity separators: Here,
one of both fields
ceases because of the flux lines running parallel to the
card's antenna. The yellow position is weak, the red ones do not
operate.
Several patent applications are granted or pending, e. g. 4327334
(Germany), 94111981 (Europe), 5,648,761 (USA).
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