Integrated Circuit Scan Cell Security via Locking Segment Insertion Bits
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Solution Overview
Problem
Existing integrated circuits face challenges in protecting hidden content, such as embedded instruments and encryption keys, from unauthorized access, particularly in IEEE 1687 networks, where attackers can quickly open segment insertion bits and map the network architecture.
Innovation Solution
The implementation of locking segment insertion bits (LSIBs) and trap bits within the scan cell circuits, which require correct key values and sequences to access hidden content, and the use of switching LSIBs that complicate attacker strategies by providing misleading or reduced feedback, increasing the time required to access hidden instruments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If segment insertion bits are implemented to enable dynamic reconfiguration of scan chains for accessing hidden content, then ease of operation is improved, but security is worsened as attackers can quickly map the network architecture
Solution Approach 1:
The patent applies preliminary action by pre-loading key values into the locking segment insertion bits during chip manufacturing or initialization. These pre-stored keys must be correctly entered to enable segment access, preventing attackers from arbitrarily opening segments to map the network architecture.
Solution Approach 2:
The patent introduces trap bits as intermediary elements between the attacker and the actual hidden content. These trap bits detect unauthorized access attempts and trigger responses that complicate the attacker's ability to map the network, serving as a mediator that protects the underlying structure.
2Object-affected harmful factors
If JTAG port is fused off to prevent unauthorized access, then security is improved, but ease of operation is worsened as the port can no longer be used for debug, configuration, or diagnosis
Solution Approach 1:
The patent applies dynamics by making the JTAG port's accessibility dynamic rather than static. The port remains physically intact and can be selectively enabled or disabled based on authentication credentials. This allows the system to transition between secure (port closed) and operational (port open) states, resolving the contradiction between security and accessibility.
3Object-affected harmful factors
If challenge-response pairs with encryption algorithms are used to protect the JTAG port, then security is improved, but device complexity is worsened
Solution Approach 1:
The patent applies parameter changes by modifying the segment insertion bit structure to include key value storage and comparison functionality. Instead of adding separate encryption hardware, the system changes the parameters of existing scan chain components to incorporate security features, thereby improving security while minimizing increases in device complexity.
Data Source
AI summary
An integrated circuit has a first scan cell segment, a second scan cell segment connected to one or more hidden content, and a scan cell circuit connected to the first scan cell segment and the second scan cell segment. The scan cell circuit alternatively provides access to the first scan cell segment and the second scan cell segment based on a state of the scan cell circuit.