DAR-SPUF: A Dynamically Adjustable Radiation-Hardening Method for SRAM-Based Physical Unclonable Functions

With the increasing demand for encrypted communication in spacecraft, aerospace-grade chips are required to integrate encryption circuits. The lightweight characteristics of static random access memory (SRAM) physical unclonable function (PUF) make it suitable for aerospace applications. However, the space radiation effects can degrade SRAM PUF key reliability and even cause stuck-bit errors. Therefore, it is necessary to harden the SRAM PUF circuit to obtain a stable encryption key. This paper presents a dynamically adjustable radiation-hardening method for SRAM PUF (DAR-SPUF). The method generates stable keys through dynamic key adjustment circuit, stuck-bit error detection circuit, and other peripheral circuits. The proposed method does not modify the structure of traditional SRAM PUF cell. Compared to existing hardening methods, the proposed method exhibits smaller area overhead and power consumption. A FinFET-based test chip was designed and fabricated to verify the effectiveness of the DAR-SPUF. The test chips were irradiated with total ionizing dose (TID) and heavy ions. The experimental results show that radiation effects increase the bit error rate (BER) of unhardened test chip by 1.34x – 2.57x. However, it reduces the BER of the hardened DAR-SPUF chip by 19.73x – 24.52x. The experimental results also demonstrate that the DAR-SPUF can mitigate the stuck-bit errors to 0.