Finger-Controlled Contactless Chip Card with Booster Antenna
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Solution Overview
Problem
Contactless smart cards face security issues due to the risk of unauthorized use through 'skimming,' as existing anti-skimming solutions are either impractical, difficult to industrialize, or inefficient, particularly since they do not effectively prevent radiofrequency communication without physical modifications or buttons.
Innovation Solution
A smart card design featuring a booster antenna not electrically connected to the electronic module, with carefully chosen inductance and capacitance values to default-detune the card from standard reader frequencies, requiring user intervention via finger placement to adjust capacitance and retune the card for communication, utilizing a booster antenna with a main inductance and an inductance concentrator connected in series or parallel with a capacitor, and additional capacitance provided by the user's fingers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the antenna is directly connected to the chip with no detuning mechanism, then the card can communicate with readers, but the card becomes vulnerable to skimming attacks
Solution Approach 1:
The card is pre-configured with a booster antenna and detuning capacitor that automatically prevent communication with readers unless the user performs a specific action (pressing the button or placing a finger). This preliminary detuning state ensures security by default, while the pre-prepared activation mechanism maintains ease of use when needed.
Solution Approach 2:
A button or finger acts as an intermediary element between the user and the antenna system. This intermediary controls the connection state of the detuning capacitor, thereby mediating between the secure detuned state and the operational tuned state without requiring direct user manipulation of the antenna itself.
2Reliability
If an on/off button is added to manually disconnect the antenna, then security is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The card uses the user's own finger as the activation mechanism. The finger's capacitance automatically adjusts the resonant frequency when placed on the card surface, eliminating the need for separate buttons or switches. This self-service approach maintains security while reducing structural complexity.
Solution Approach 2:
The card's antenna system serves multiple functions: it provides contactless communication when activated and acts as a security barrier when deactivated. The same antenna structure fulfills both security protection and data transmission roles, eliminating the need for separate components.
3Ease of operation
If the resonant frequency is adjusted to match reader frequency, then communication is enabled, but the card becomes susceptible to unauthorized use
Solution Approach 1:
The resonant frequency of the card is made dynamic rather than fixed. It can switch between a detuned state (for security) and a tuned state (for communication) based on user activation. This dynamic adjustment prevents skimming attacks while maintaining communication capability when needed.
Solution Approach 2:
The electrical parameters of the antenna circuit, specifically the resonant frequency, are changed based on activation state. When the detuning capacitor is disconnected (activated), the resonant frequency shifts to match the reader frequency, enabling communication. When connected (deactivated), the frequency is detuned to prevent communication and skimming.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively prevents unauthorized use by ensuring the card is initially detuned from standard frequencies, allowing secure operation only when the user intentionally adjusts the resonance frequency, enhancing security and manufacturing efficiency without requiring physical buttons or complex structures.
Implementation Method 1
the values of L1, L2 and C are chosen on the one hand to obtain said resonant frequency F0, and on the other hand so that the parallel connection of said predetermined capacitance Cd brings the resonant frequency of the card close to said frequency F0' of the signal emitted by said reader
Implementation Method 2
the smart card comprises a booster antenna provided with a main antenna of inductance L1 and a concentrator antenna of inductance L2, connected in series or parallel with a capacitance C
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a contactless chip card intended to communicate with a chip card reader operating at a resonant frequency F0', said chip card being provided with a card body integrating at least one antenna connected in series or in parallel with a capacitor, the values of the inductances of the antennae and the capacitance of the capacitor being chosen to obtain a resonant frequency F0 that is far enough from the frequency of the signal emitted by the reader to limit radiofrequency communication with the reader, so that the chip card is by design out of tune with respect to the reader, and the values of said inductances and capacitance furthermore being chosen so that the connection in parallel of an additional predetermined capacitance Cd brings the resonant frequency of the card into the vicinity of the frequency F0' of the signal emitted by said reader so that the chip card becomes tuned to the reader, characterised in that the chip card includes a booster antenna (20) provided with an inductive main antenna U and with an inductive concentrator antenna L2, which antennae are connected in series or parallel with a capacitor C, and in that the inductances of L1 and L2 and the capacitance of C are chosen on the one hand to obtain said resonant frequency F0, and on the other hand so that the connection in parallel of said predetermined capacitance Cd brings the resonant frequency of the card into the vicinity of said frequency F0' of the signal emitted by said reader.