Hardware Key Interface for Anti-Tamper Authentication
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Solution Overview
Problem
Existing electronic equipment protection methods, such as mechanical locks, do not effectively prevent reverse engineering through externally accessible interfaces like JTAG, as these interfaces can be exploited to access and modify internal components.
Innovation Solution
A system incorporating anti-tamper functionality and a hardware key interface that determines authorized access by communicatively coupling with a hardware key, allowing only permitted access modes based on the key's presence and information, thereby securing application-specific functionality and preventing unauthorized interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical lock is used to prevent physical access to the case, then physical security is improved, but access control for externally accessible interfaces remains insufficient
Solution Approach 1:
The patent replaces the mechanical lock system with a hardware-based cryptographic authentication system. Instead of relying solely on mechanical case locking, the system uses a hardware key interface that requires physical insertion of an authorized hardware key into a key interface within the case. This hardware key contains cryptographic material that enables authentication for accessing externally accessible interfaces like JTAG debug interfaces, thereby substituting mechanical security with cryptographic security.
Solution Approach 2:
The patent introduces a hardware key as an intermediary between the external environment and the internal electronics. The hardware key serves as a mediator that must be physically inserted into a key interface to authorize access. This intermediary hardware key contains cryptographic material that enables or disables access to externally accessible interfaces, creating an additional layer of security that bridges the gap between mechanical case locking and interface-level access control.
2Ease of operation
If externally accessible debug interfaces are provided for inspection and modification, then ease of operation and debugging capability are improved, but security against reverse engineering deteriorates
Solution Approach 1:
The patent implements dynamic access control for externally accessible interfaces based on the presence and state of the hardware key. The system can operate in different modes (e.g., normal mode, test mode, locked mode) that dynamically enable or disable access to interfaces like JTAG. When an authorized hardware key is inserted, the system transitions to a state that permits debugging operations. When the hardware key is removed or unauthorized, the system dynamically restricts access to externally accessible interfaces, thereby providing conditional access control.
Solution Approach 2:
The patent changes the access parameter of externally accessible interfaces based on hardware key authentication. The system monitors whether an authorized hardware key is present in the key interface and uses this information to change the accessibility parameter of debug interfaces. When authentication succeeds, the accessibility parameter is set to enabled, allowing debugging operations. When authentication fails or the key is removed, the accessibility parameter is set to disabled, preventing reverse engineering attempts.
3Reliability
If hardware key authentication is implemented to control access modes, then security against unauthorized access is improved, but device complexity increases
Solution Approach 1:
The patent uses a hardware key that contains a copy of cryptographic material (such as an encryption key or authentication token) that is distributed to authorized devices. Instead of implementing complex cryptographic protocols from scratch, the system uses pre-loaded hardware keys that contain authenticated copies of security material. This hardware key can be inserted into the key interface to prove authorization without requiring complex on-chip cryptographic processing, thereby reducing system complexity while maintaining security.
Solution Approach 2:
The patent extracts the cryptographic authentication function from the main system and places it in a separate, dedicated hardware key device. This extracted hardware key contains the cryptographic material and can be physically separated from the main system. By taking out the authentication function into a separate hardware component, the main system doesn't need to incorporate complex cryptographic circuits, thereby reducing overall device complexity while maintaining strong security through the external hardware key.
Data Source
AI summary
In one embodiment, a system comprises application-specific functionality, anti-tamper functionality to detect an unauthorized attempt to interact with the application-specific functionality; and a hardware key interface to communicatively couple the system to a hardware key. An attempt to interact with the application-specific functionality is considered unauthorized if an authorized hardware key is not communicatively coupled to the hardware key interface when the attempt occurs.