Chip Gallery

A Synthesizable Thyristor-Like Leakage-Based True Random Number Generator

As the demand for random data in cryptographic systems continues to rise, the importance of True Random Number Generators (TRNGs) becomes increasingly crucial for securing cryptographic applications. However, designing a TRNG that is reliable, secure, and cost-effective presents a significant challenge in hardware security. In this paper, we propose a synthesizable TRNG design based on a thyristor-like leakage-based (TL) structure, optimized for secure applications with small area and cost-efficiency. Our design has been validated using a 65-nm CMOS process, achieving a throughput of 0.397-Mbps within a compact area of 14.4-μm2, offering considerable cost savings while maintaining high randomness and area-throughput trade-off of 27.57 Gbps/mm2. Moreover, this TRNG can be synthesized as a standard cell through a semi-custom design flow, significantly reducing design costs and enabling design automation, which streamlines the process and reduces the time and effort required compared to traditional full-custom TRNGs. Additionally, as it is library characterized, the number of TL TRNG cells can be freely adjusted to meet specific application requirements, offering flexibility in both performance and scalability. To assess its randomness, the NIST statistical test suite was applied, and the proposed TL TRNG successfully passed all applicable tests, demonstrating its randomness. 

S. Kim, J. H. Kim, J. Lee, “A Synthesizable Thyristor-Like Leakage-Based True Random Number Generator,” IEEE/ACM Design, Automation and Test in Europe (DATE), Mar. 2025.

A current-integrated differential NAND-structured PUF for stable and V/T variation-tolerant low-cost IoT security

We designed a current-integrated differential NAND-structured physically unclonable function (PUF) with lossless stabilization for cost-efficient IoT security. The area-efficient NAND array structure with 20F2 area per bit and lossless stabilization through remapping achieves both high cost efficiency and reliability. By utilizing the drain current (IDS) with near-threshold (near-VTH) bias, which is exponentially dependent on VTH, a pair of minimum-sized PMOS from the NAND array generated a stable response with a wide IDS mismatch. With the IDS integration, stability of a response is quantized to enable lossless stabilization through remapping. The proposed PUF achieved a bit error rate (BER) of 0.12% and an unstable bit rate (UBR) of 0.97% with remapping and TMV11. Also, supply voltage and temperature (V/T) variation immunities of 0.145%/0.1V and 0.120%/10℃, respectively, were observed, which represent 2.9×/2.5× improvements from an earlier NAND-structure PUF without stabilization. 

J. Lee, Y. Lee, “A current-integrated differential NAND-structured PUF for stable and V/T variation-tolerant low-cost IoT security ,” IEEE Asian Solid-State Circuits Conference (A-SSCC), Nov. 2021.

Jongmin. Lee, Minsun Kim, Minhyeok Jeong, Gicheol Shin, Yoonmyung. Lee, “A 20F2/bit Current-Integration-Based Differential NAND-Structured PUF for Stable and V/T Variation-Tolerant Low-Cost IoT Security” IEEE Journal of Solid-State Circuits (JSSC), Invited Paper to the Special Section on A-SSCC, Oct. 2022.

A 354F² Leakage-based Physically Unclonable Function with Lossless Stabilization Through Remapping for IoT Security

We revised a leakage-based physically unclonable function (PUF) with 354F2 area per bit to provide cost-effective security for IoT devices. By exploiting the exponential dependence of subthreshold leakage current on a transistor’s threshold voltage variations, a response key bit is generated with only 354F2 silicon area. Moreover, to improve stability without discarding Challenge-Response Pairs (CRPs), a novel lossless stabilization scheme called ‘remapping’ is proposed. The proposed leakage-based PUF exhibited a 3.87% native unstable bit ratio (UBR) and 0.426% native bit error rate (BER). With the proposed remapping and 11-bit temporal majority voting applied, the BER and UBR are significantly improved to 47 ppm and 538 ppm, respectively, achieving stability as high as a conventional trimming approach without any key losses. 

Jongmin Lee, Donghyeon Lee, Yongmin Lee, Yoonmyung Lee, “A 354F2 Leakage-Based Physically Unclonable Function with Lossless Stabilization through Remapping for Low-Cost IoT Security” IEEE Journal of Solid-State Circuits (JSSC), Feb. 2021.

An 20F² Area-Efficient Differential NAND-Structured Physically Unclonable Function for Low-Cost IoT Security

We designed a differential NAND-structured physically unclonable function (PUF) with 20F2 area per bit for cost-effective IoT applications. With the area-efficient NAND-array structure, a key bit is generated from a pair of minimum-sized NMOS transistors by effectively amplifying threshold voltage (Vth) mismatch. By utilizing the near-threshold current of the examined transistors, high sensitivity to Vth variation, which is desired for stability, and faster operation than leakage current based PUFs is achieved. An offset-compensated comparison scheme is provided to accurately determine the key value without bias. The proposed PUF achieves 0.06% BER and 0.53% unstable bits with TMV11 while reducing the area by an order of magnitude compared with state-of-the-art CMOS-based PUFs 

J. Lee, M. Kim, G. Shin, Y. Lee, “A 20F2 Area-Efficient Differential NAND-Structured Physically Unclonable Function for Low-Cost IoT Security ,” IEEE European Solid-State Circuits Conference (ESSCIRC), Sep. 2019.

Jongmin Lee, Minsun Kim, Gicheol Shin, Yoonmyung Lee, “A 20F2 Area-Efficient Differential NAND-Structured Physically Unclonable Function for Low-Cost IoT Security ,” IEEE Solid-State Circuits Letters (SSC-L), Sep. 2019. (Cross-published)

A 445F² Leakage-based Physically Unclonable Function with Lossless Stabilization Through Remapping for IoT Security

We designed a leakage-based physically unclonable function (PUF) with 445F2 area per bit for low-cost IoT security. A lossless stabilization is achieved by novel remapping scheme where PUF cells in unstable challenge-response pairs (CRPs) are remapped to construct stable CRP, avoiding costly CRP loss in conventional trimming approach. Thanks to the lossless stabilization scheme, proposed PUF achieves 0.004% BER and 0.04% unstable cells with zero CRP loss by applying remapping for 10% of CRPs and TMV11.

J. Lee, D. Lee, Y. Lee, Y. Lee, “A 445F2 Leakage-Based Physically Unclonable Function with Lossless Stabilization through Remapping for IoT Security,” IEEE International Solid-State Circuits Conference (ISSCC), Feb. 2018.