R&D: Concealable Physical Unclonable Functions using Vertical NAND Flash Memory

Nature Communications has published an article written by Sung-Ho Park, Ryun-Han Koo, Department of Electrical and Computer Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul, Republic of Korea, Yeongheon Yang, Research and Development Division, SK hynix Inc., Icheon, Republic of Korea, Jiseong Im, Jonghyun Ko, and Jong-Ho Lee, Department of Electrical and Computer Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul, Republic of Korea.

Abstract: “Physical Unclonable Functions (PUFs) can address the demand for enhanced hardware security. Vertical NAND (V-NAND) flash memory is the most commercialized non-volatile memory. However, it has been optimized to reduce cell-to-cell variation for stable data storage, which presents challenges for its application as a PUF, as PUFs inherently rely on such variations. Here, we propose a concealable PUF using V-NAND flash memory by generating PUF data through weak Gate-Induced-Drain-Leakage (GIDL) erase. The differences in doping depth among V-NAND strings arising from the fabrication cause variations in GIDL erase performance. The resulting V-NAND PUF demonstrated ideal security characteristics while maintaining 100% accuracy under variations in read count and temperature. Concealment is achieved by overwriting the PUF data with other data, and perfect conceal-reveal characteristics are maintained over 10² cycles. Concealable V-NAND PUF not only prevents attacks when the PUF is not in use but also allows the memory to be utilized as storage.“