EMV Bank Card Display with Secondary Microcontroller
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Solution Overview
Problem
EMV standard bank cards lack additional input/output ports, making it impossible to drive a display for showing last transactions due to security constraints, which limits their functionality in displaying transaction information.
Innovation Solution
A second microcontroller is added to the chip card to perform a card reader function, accessing public transaction data, and an actuator like a motion sensor or light sensor is used to trigger the display of this information, with communication interfaces conforming to ISO standards to ensure security and compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a second microcontroller is added to read and display transaction data, then the card can display last transactions, but the device complexity increases
Solution Approach 1:
The system is divided into two separate microcontrollers: a secure microcontroller that handles EMV transactions and stores data, and a display microcontroller that reads public transaction data and controls the display. This segmentation allows the secure chip to maintain its security constraints while enabling display functionality through a dedicated display controller.
Solution Approach 2:
The display microcontroller acts as an intermediary between the secure EMV chip and the display device. It reads public transaction data from the secure chip through controlled interfaces and processes this data for display, without compromising the security of the secure chip.
2Adaptability or versatility
If additional input/output ports are added to the secure chip, then the display can be driven, but the security of the EMV standard is compromised
Solution Approach 1:
The display control functionality is extracted from the secure microcontroller and placed in a separate display microcontroller. The secure chip only provides data through its existing standardized interfaces, while the display microcontroller handles all display-related operations, thus extracting the security-critical functions from the display path.
Solution Approach 2:
The display microcontroller serves multiple functions: it reads public transaction data from the secure chip, processes the data, controls the display device, and manages user interactions. This multi-functionality in a non-secure component enables display capabilities without requiring the secure chip to have additional specialized interfaces.
3Loss of information
If public information is accessed for display, then transaction data can be shown, but the risk of information exposure increases
Solution Approach 1:
The system implements different access levels for different data: private sensitive data remains exclusively in the secure microcontroller and is never exposed, while public transaction information is made accessible to the display microcontroller through controlled interfaces. This local quality differentiation ensures that only appropriate information is exposed.
Solution Approach 2:
The secure microcontroller provides feedback to the display microcontroller about which data should be considered public and can be displayed. This feedback mechanism ensures that the display microcontroller only accesses and displays information that has been explicitly marked as public by the secure chip, preventing unauthorized information exposure.
Data Source
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AI summary
To allow the display of the latest transactions, a chip card 100c for secure transaction comprises at least one secure chip 101c, for example of EMV type, furnished with at least one communication interface so as to be able to communicate with a card reader so as to perform a transaction, an electronic display 103, an autonomous battery 104, a card reader circuit 150c connected to a communication interface of the secure chip so as to be able to access information contained in the secure chip so as to be able to display same on the display.