Closed-Slot Antenna Electrode Injector for Compact Chassis RF Coupling
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Solution Overview
Problem
Existing hardware wallets for cold storage of private keys offer poor ergonomics, making transactions difficult due to small displays and the requirement for two buttons, while devices with advanced ergonomics lack the same rigorous security as hardware wallets.
Innovation Solution
A hardware wallet with a touchscreen controlled exclusively by a secure element, using serial links to manage the display and touch module, and emulating button presses through the touchscreen for secure operation, combined with a closed-slot antenna for wireless communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hardware wallet uses a microcontroller with USB interface to manage communication and peripherals, then the device offers advanced ergonomics and connectivity, but the security level decreases because the microcontroller can be attacked and compromised
Solution Approach 1:
The device is divided into two distinct parts: a secure element that handles cryptographic operations and private key storage, and a microcontroller that manages communication and peripherals. This segmentation isolates the security-critical functions from potential attacks on the microcontroller, resolving the contradiction between ergonomics and security.
Solution Approach 2:
The secure element acts as an intermediary between the microcontroller and the external world. The microcontroller can communicate with peripherals and users, but all sensitive operations must go through the secure element, which verifies their authenticity. This mediator role allows advanced ergonomics while maintaining security.
2Reliability
If a hardware wallet uses a secure element with limited I/O resources, then the security level is maintained, but the device complexity increases due to the need for a microcontroller proxy
Solution Approach 1:
The microcontroller serves multiple functions: it manages USB communication, controls the display, operates buttons, and coordinates with the secure element. By making the microcontroller multi-functional, the design accepts increased device complexity in exchange for maintaining security through the secure element's limited I/O interface.
3Volume of moving object
If the antenna is positioned close to the chassis wall to save space, then the device compactness is improved, but the antenna performance deteriorates due to reduced radiation efficiency
Solution Approach 1:
Instead of using a traditional monopole antenna that requires space away from the chassis, the patent uses a closed-loop slot antenna whose equivalent current distribution replicates the radiation pattern of a monopole antenna. This copying approach allows the antenna to be positioned close to the chassis wall while maintaining radiation efficiency.
Solution Approach 2:
The patent transforms the antenna geometry from an open monopole structure to a closed-loop slot structure. This parameter change in the antenna's physical configuration allows it to achieve the same radiation characteristics while being positioned differently relative to the chassis, thus resolving the space vs. performance contradiction.
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
The solution provides enhanced user interface comfort with a large touchscreen and secure operation, maintaining high security standards by isolating the touchscreen from potential microcontroller attacks.
Implementation Method 1
a compression element of a flexible and elastic material, arranged between the two electrodes and exerting on them a spreading force which presses the first electrode against the first surface of the longitudinal port and presses the second electrode against the second surface of the longitudinal port
Implementation Method 2
a closed-slot antenna for transmitting or receiving data in a specified frequency band, made in the side wall of the chassis and having a radiation axis substantially perpendicular to the side wall
Data Source
AI summary
An electronic device comprising a chassis receiving a closed-slot antenna comprising a longitudinal port made in and through a side wall of the chassis. The antenna comprises a radio frequency signal injector comprising two substantially parallel flat electrodes, the first electrode resting on a first surface of the longitudinal port and the second electrode resting on a second surface of the longitudinal port. A compression element made of a flexible and elastic material, arranged between the two electrodes, exerts a spreading force on them which presses them against the first and second surfaces of the longitudinal port.