Invisible scan architecture for secure testing of digital designs

Abstract

Various embodiments of the present disclosure provide a scan-based architecture for register-transfer-level (RTL) or gate-level designs that improves the security of scan chain-based design-for-testability (DFT) structures. In various embodiments, the scan-based architecture includes invisible scan chains that are hidden in such a way that an attacker cannot easily identify or locate the invisible scan chains for exploitation and revealing internal secure information of the design. The invisible scan chains are dynamically configurable into a scan chain with select flip-flops, such that scan paths of the invisible scan chains may be different between different designs, chips, or testing operations. Various embodiments further employ key-based obfuscation by combining a scan control finite state machine with existing state machines within a design, which improves design security against unauthorized use and increases confidentiality. Specific sequences of key patterns cause the design to transition into a test mode or a normal mode.