arXiv subjects

Amarin Laohajirapan

Publications and source records attributed to Amarin Laohajirapan.

2 recordsLinked to original sources

arXiv2026

Resolving Conflicts Between RTOS Timekeeping and Uninterruptable Trusted Computing

Trusted Execution Environments (TEEs) on low-power microcontrollers (e.g., ARM TrustZone-M) enable isolation of Secure and Non-Secure software but still require both worlds to share resources, including interrupt controllers. In this model, real-time applications and real-time operating systems (RTOS-s) are executed in the Non-Secure sub-system, whereas the Secure sub-system is typically reserved for a small set of pre-defined security (e.g., cryptographic) operations referred to as trusted computing services. However, many RTOS-s rely on periodic interrupts (SysTicks) to advance their own notion of time (time-keeping), and the delivery of this interrupt is essential for preserving real-time behavior. On the other hand, the security of many trusted computing services requires atomicity vis-a-vis the Non-Secure sub-system (where the RTOS resides), precluding SysTick handling. This paper first characterizes this conflict and then introduces a Secure-driven time synchronization mechanism in which the Secure World measures elapsed time and compensates the Non-Secure RTOS by unobtrusively updating the RTOS time-keeping data structures with the appropriate number of missed ticks before re-enabling interrupts and resuming the execution of the Non-Secure system. This approach restores a consistent, monotonic notion of time across worlds and enables secure coexistence of trusted computing services and RTOS-s on microcontrollers. Importantly, the proposed approach requires no modifications to the underlying RTOS and yields no significant run-time overhead.

cs.CR↗

arXiv2026

SMARM+: Analyzing and Enhancing Shuffled Measurements for Remote Attestation in Real-Time IoT Settings

Remote attestation (RA) is a lightweight security primitive for detecting software compromise on IoT devices. Traditional RA schemes require atomic, non-interruptible memory measurements, making them difficult to deploy alongside real-time workloads. SMARM addresses this limitation by measuring memory in a secret, shuffled block order, reducing the non-interruptibility period to the duration of a single block measurement. However, SMARM was originally designed for microkernel-based systems and has not been studied in RTOS-driven real-time environments. In this work, we present the first systematic study of SMARM in real-time RTOS-based setups. We implement SMARM on commodity ARM TrustZone-M hardware running FreeRTOS and Zephyr, and introduce the Frequency Accuracy Ratio (FAR) to quantify the extent to which attestation can coexist with real-time execution under varying workloads. Our evaluation shows that SMARM's real-time compatibility is highly sensitive to block size: large blocks significantly degrade real-time availability, while small blocks incur substantial secure-storage overhead, limiting deployability on memory-constrained devices. To address this limitation, we propose SMARM+, a family of enhanced SMARM variants consisting of SMARM+PRNG and SMARM+FPE. They are designed to reduce secure-storage requirements while preserving SMARM's security guarantees and real-time behavior. Our evaluation highlights the trade-off between secure-storage reduction, attestation runtime, and energy overhead, and provides guidance on selecting among SMARM, SMARM+PRNG, and SMARM+FPE for different deployment settings.

cs.CR↗