Scan Chain Security via Shadow Register Authentication
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Solution Overview
Problem
Existing scan architectures for testing integrated circuits (ICs) pose a security risk as they provide unauthorized access to device components, potentially compromising design security.
Innovation Solution
The implementation of a device with a scan chain, a shadow shift register, a signature register, and a comparator, where the shadow shift register is loaded during the scan in phase and the signature register is loaded during the capture phase, allowing only authorized access by matching the shadow shift register value with the signature register value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a scan chain is provided for testing ICs, then testability is improved, but security is worsened due to unauthorized access
Solution Approach 1:
A buffer element is introduced as an intermediary between the scan chain output and the external tester. This buffer acts as a security gatekeeper that mediates data flow based on authentication credentials, allowing legitimate testing while blocking unauthorized access attempts.
Solution Approach 2:
The scan chain incorporates self-service security mechanisms including credential verification and automatic authorization checks. The system performs its own authentication without external intervention, verifying credentials against stored authentication data and automatically controlling buffer enablement based on verification results.
2Object-affected harmful factors
If security measures are added to prevent unauthorized access, then security is improved, but device complexity is worsened
Solution Approach 1:
Security functions are merged with existing scan chain infrastructure. The buffer element integrates with the scan chain output, and authentication credentials are stored within the same device structure. This combining approach adds security without requiring entirely separate security subsystems.
Solution Approach 2:
The buffer element serves multiple functions: it acts as a security gate for authentication, a data latch for credential storage, and a control element for managing scan chain output. This multi-functionality reduces the need for additional dedicated security components.
Data Source
AI summary
A device includes a scan chain including a plurality of storage elements and an output buffer; a shadow shift register having a shadow shift input coupled to a scan output of one of the storage elements of the scan chain; a signature register; and a comparator having a first input, a second input, and an output. The comparator first input is to receive a value of the shadow shift register, and the comparator second input is to receive a value of the signature register. The output buffer has a control input coupled to the comparator output, and the output buffer provides a high-impedance output responsive to the value of the shadow shift register being unequal to the value of the signature register.