Lightweight Memory Obfuscation Using PUF-Based XOR Encryption

Abstract

Securing memory in resource-constrained embedded systems remains a critical challenge due to the susceptibility of statically stored cryptographic keys to physical and sidechannel attacks. This paper presents a lightweight memory obfuscation architecture based on Physical Unclonable Functions (PUFs), utilizing the intrinsic manufacturing variations of Arbiter PUFs (APUFs) to generate device-specific encryption keys dynamically at runtime, thereby eliminating the need for persistent key storage. The proposed system employs a hardware-rooted XOR-based encryption scheme in which memory addresses are transformed into challenges to produce unique, non-stored keystreams for memory protection. The architecture is implemented on an FPGA platform using a MicroBlaze-based system, integrating a custom XOR encryption engine and a finite state machine (FSM) for secure access control and device authentication. Experimental results demonstrate strong statistical security properties, with ciphertext achieving near-ideal entropy (7.9987 bits/byte), negligible correlation with plaintext, and a uniform distribution under chi-square testing. Furthermore, the design exhibits low hardware overhead, utilizing only 3.15% of LUT resources and consuming 0.235 W, highlighting its suitability for IoT and resource-constrained applications. These results confirm that PUF-based dynamic key generation combined with lightweight XOR encryption provides an effective and efficient hardware-rooted solution for memory protection.