Covert Communication Attacks in Chiplet-based 2.5-D Integration Systems

The successful operation of chiplet-based 2.5-D integration systems heavily depends on the design of power delivery networks (PDNs) that can deliver multiple voltage levels to various chiplets while satisfying unique noise and performance requirements. However, despite the importance, security is often overlooked in the design of these systems. A novel covert communication channel in 2.5-D integration systems, which utilizes the coupling effects within an interposer PDN, is uncovered in this paper. Particularly, by varying the power consumption of one chiplet at the transmitting side and measuring the fluctuations in the supplied voltage on another chiplet at the receiving side, an unauthorized content can be transmitted between different chiplets connected to the common interposer PDN. An analytical model based on multi-port network theory, which can quantitatively predict the amount of coupling between various pairs of chiplets, is proposed. The proposed modeling technique is compared with extensive simulations in a case study.