Highly Scalable Runtime Countermeasure Against Microprobing Attacks on Die-to-Die Interconnections in System-in-Package

The emerging System-in-Package (SiP) technology has enabled multiple dies fabricated on a single chip for high performance and energy efficiency. Die-to-die (D2D) communication in SiP is typically unencrypted, exposing sensitive data to possible microprobing attacks. In this paper, we propose an on-chip microprobe detection circuit together with a noise canceling technique to protect D2D buses for future SiP security. The proposed method utilizes the metastable state of a flip-flop to detect the small timing variation caused by the inevitable loading effect of a microprobe. This design requires minimum digital resources with high scalability. Uniquely, the proposed design protects D2D buses at runtime without interfering with normal data transfers. In addition, it introduces zero latency to the communication channel. We built the detection circuit in a Xilinx ZYNQ Ultrascale+ SoC to prove its feasibility. Dynamic partial reconfiguration function is employed to create the test platform and emulate D2D interconnections as well as microprobing attacks on them. To demonstrate its potential to be used in standard communication protocols, we integrated the detection circuit with a fully functional Advanced eXtensible Interface (AXI) bus. Experimental results show that the proposed runtime detection method is effective, resource-efficient, and reliable under temperature-varying environments.