Embedding Security Keys in Memory... Professor Jong-Ho Lee's Team at SNU ECE Develops World’s First NAND Flash-Based “Concealable PUF” Technology
- Introduces a next-generation hardware security solution with both high security and spatial efficiency
- Expected to be applied to electronic device security in smartphones, vehicles, IoT, and more
- Research published in Nature Communications, a leading international journal

▲ Professor Jongho Lee (left) and researcher Seongho Park (right) from the Department of ECE, SNU

The College of Engineering at Seoul National University announced that Professor Jong-Ho Lee's team from the Department of Electrical and Computer Engineering has developed a novel hardware security technology based on commercial 3D NAND flash memory (V-NAND flash memory). The technology, named “Concealable Physical Unclonable Function (Concealable PUF)”, preserves the core strengths of traditional PUFs—namely unclonability and randomness—while introducing a groundbreaking feature: the ability to conceal the security key and reveal it only when needed. This is the first-ever implementation of such functionality using V-NAND flash memory. The results of this research were published on June 3 in Nature Communications, one of the world’s leading scientific journals.

■ Research Background

With the rapid advancement of artificial intelligence and big data, the use of data is growing exponentially, bringing data security into sharp focus. As a result, stronger security technologies are required beyond traditional password-based methods. One such emerging solution is the Physically Unclonable Function (PUF). PUFs generate unique values based on minute physical variations that naturally occur during semiconductor manufacturing processes, making them virtually impossible to replicate or predict. However, conventional PUFs have primarily been implemented in laboratory-scale devices, making mass production difficult, and they have faced limitations in safely concealing security keys.

■ Research Achievements

To overcome the limitations of conventional PUFs, the research team developed the Concealable PUF by leveraging a unique property of V-NAND flash memory: the Gate-Induced Drain Leakage (GIDL) mechanism used in the erase operation. By weakly applying GIDL, they intentionally amplified the variations in erase behavior across memory cells, thereby generating PUF data.

This innovation is particularly significant because it allows PUF functionality to be implemented directly within widely used V-NAND flash memory—without requiring any changes to its circuits or structure. One of the most compelling advantages is the ability to expose the security key only when needed, while concealing it under user data during normal operation. This dual-mode capability maximizes both security and spatial efficiency. Notably, the memory space used for the concealed key can also serve as regular storage when the key is not in use, enabling efficient system design without wasted capacity.

The team conducted experiments using commercial V-NAND flash memory, demonstrating that the generated PUF data maintained 100% accuracy and randomness under a wide range of conditions—including temperature changes from 25°C to 85°C and over 10 million repeated read cycles. They also verified the technology’s stability through more than 100 iterations of the conceal-and-restore process, with the original key restored without error each time.

In simulated attacks using machine learning-based methods, the PUF data proved highly secure: prediction accuracy remained at the level of random guessing, confirming the strong security resilience of the Concealable PUF.

■ Expected Impact

This breakthrough enables the creation of a highly reliable security system that can generate, store, and conceal security keys using existing commercial memory devices, without requiring any hardware modifications. As such, the technology is expected to be widely applicable across a broad range of security-critical electronic devices, including smartphones, vehicles, and Internet of Things (IoT) devices. Looking ahead, the research team plans to expand the application of Concealable PUF technology to a variety of hardware security solutions, further advancing the field of secure system design.

■ Researchers' Remarks

Professor Jongho Lee, who led the study, stated, “The Concealable PUF stands out for its creativity and practicality, as it can be implemented using currently mass-produced vertical NAND flash memory technology without modification. We expect it to see widespread use in the field of information security.” Lead author Seongho Park added, “This research is particularly meaningful because it demonstrates that PUFs can be constructed using the erase operation of standard V-NAND flash memory—without altering circuit designs or structures. In particular, the concealment feature, which ensures that the security key is exposed only when needed, opens up new possibilities for PUF technology in terms of both security and space efficiency.”

■ Researcher Career Path

Researcher Seongho Park is currently enrolled in the combined Master’s-Ph.D. program in the Department of Electrical and Computer Engineering at Seoul National University. In addition to improving the characteristics of V-NAND flash memory, he is actively conducting research in a range of applied areas, including neuromorphic computing and data security.

▲ Figure 1. Concealable PUF Based on V-NAND Flash Memory Using GIDL Erase. (a) Schematic illustration of the concealable PUF using V-NAND flash memory. (b) Circuit diagram of the V-NAND flash memory. (c) The GIDL erase method.

▲ Figure 2. PUF Key Generation Using GIDL Erase and Operational Mechanism of the V-NAND Flash Memory-Based PUF. (a) Threshold voltage (V_th) distribution of V-NAND flash cells after weak GIDL erase. (b) Comparison between conventional NAND flash-based PUF and the proposed method. (c) Operational mechanism of the V-NAND flash memory-based PUF. (d) Autocorrelation test results of the generated PUF key.

[References]

Paper Title / Journal: “Concealable physical unclonable functions using vertical NAND flash memory”, Nature Communications
DOI: https://doi.org/10.1038/s41467-025-60415-y

[Contact]

Seongho Park, Advised by Professor Jongho Lee, Department of Electrical and Computer Engineering, Seoul National University: thomasung@snu.ac.kr

Source: https://ece.snu.ac.kr/ece/news?md=v&bbsidx=56596
Translated by: Dohyung Kim, English Editor of the Department of Electrical and Computer Engineering, kimdohyung@snu.ac.kr