Hardware security tech can hide and reveal encryption keys on demand using 3D flash memory

Seoul National University College of Engineering announced that a research team has developed a new hardware security technology based on commercially available 3D NAND flash memory (V-NAND flash memory).

Named “Concealable Physical Unclonable Function (Concealable PUF),” this technology maintains the core advantages of conventional PUFs—unclonability and randomness—while adding a novel feature: the ability to hide the security key and reveal it only when needed. This marks the world’s first implementation of such functionality on V-NAND flash memory.

The study was published online on June 3 in Nature Communications. The study was by Professor Jong-Ho Lee’s research team from the Department of Electrical and Computer Engineering.

With the rapid advancement of AI and big data, the use of data has skyrocketed, making data security more critical than ever. Traditional password systems are proving insufficient, and PUF technology has emerged as a promising alternative. PUFs leverage the tiny, naturally occurring physical differences in semiconductor manufacturing to generate unique values that cannot be cloned or predicted. However, conventional PUFs have been largely limited to lab-scale devices, facing challenges in mass production and secure key concealment.

To overcome these limitations, the research team employed a weak application of the GIDL (Gate-Induced Drain Leakage) erase mechanism in V-NAND flash memory to deliberately amplify the variation in erase levels between memory cells, thereby enabling the generation of PUF data.

Significantly, this approach requires no changes to the circuitry or structure, allowing the PUF to be implemented directly on widely used V-NAND flash memory. A major advantage of this method is that the security key can be hidden under user data when not in use and revealed only when needed. This optimizes both security and memory space efficiency. The same memory space used for storing security keys can be repurposed for general data storage, allowing for a more efficient system design.

The researchers validated their approach using commercial V-NAND flash memory. The generated PUF data maintained 100% accuracy and randomness across various conditions, including temperature variations from 25°C to 85°C and over 10 million read cycles.

The key conceal-and-reveal function was successfully repeated over 100 times without error, demonstrating the technology’s reliability. Furthermore, simulated machine learning attacks were only able to predict the keys at a level consistent with random guessing, confirming the high security of the Concealable PUF.

By enabling secure generation, storage, and concealment of keys on commercially available memory components, this high-reliability system has strong potential for deployment in smartphones, vehicles, and IoT devices requiring robust security. The research team plans to expand the application of Concealable PUF technology to a broader range of hardware security solutions.

Professor Lee stated, “Concealable PUF stands out for its creativity and practicality, as it utilizes mass-produced vertical NAND flash memory technology without modifications. We expect it to be widely adopted in the field of information security.”

Lead author Sung-Ho Park added, “This research is significant because it demonstrates how PUFs can be implemented using the erase operation of existing V-NAND flash memory without altering the circuitry or design. By enabling selective exposure of the security key, our method opens up new possibilities for enhancing both security and memory efficiency.”

Park is currently pursuing an integrated master’s and doctoral program in the Department of Electrical and Computer Engineering at Seoul National University. His research interests include improving the characteristics of V-NAND flash memory, neuromorphic computing, and data security.