Standard cell implementation of buskeeper PUF with symmetric inverters and neighboring cells for passing randomness tests

This paper demonstrates an implementation of physical unclonable function (PUF) using complementary organic transistors operating at low-voltage. PUF is an essential security element, and is important for various applications of organic devices. We implement a simple buskeeper PUF, which consists of two inverters. We confirm that the PUF bit values on the test chip can be read at a standard voltage for electronic circuits (3.3 V) via a standardized circuit board interface. We observed a low static current consumption (11.8 μA/90 bits) for the PUF chip. The PUF performance, chip-to-board interface performance, and requirements for the board interface in an organic transistor chip are discussed based on the measurement results of the test chip.

Section: Buskeeper Pufmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Feasibility of a low-power, low-voltage complementary organic thin film transistor buskeeper physical unclonable function

Ogasahara

Kuribara

Shintani

et al. 2019

“…24) Generally, the intermediate gate input voltage causes significant through-currents, resulting in a severe static leakage current. Previously, evaluated the feasibility of security components 25,26) using the OTFT logic circuits at V dd = 3.3 V with the complementary gate structure. 27) These security components called buskeeper physically unclonable functions generate random IDs unique to each chip, utilizing the power-on initial value of the buskeeper cell.…”

Section: Introductionmentioning

confidence: 99%

Yield and leakage current of organic thin-film transistor logic gates toward reliable and low-power operation of large-scale logic circuits for IoT nodes

Ogasahara¹,

Kuribara²,

Oshima³

et al. 2022

Self Cite

This paper reports on a strategy for yield improvement and static leakage current reduction by using a standard cell design for large-scale organic thin-film transistor (OTFT) circuits. Printable or flexible devices are suitable for IoT nodes, and digital OTFT circuits comprise the peripheral circuits of such devices. Sufficiently high yields and low static power consumptions are essential for battery operations of IoT nodes having functional digital circuits. Our design method to address the weak n-type OTFT on-current results in improved logic gate yields without any cell area increase. We improved the yield of the inverter, NAND, and NOR gates using a standard cell design, and achieved a 100%yield for the inverter and NOR gates and 88%yield for the NAND gates. Signal propagations with rail-to-rail operation were measured on test chips. Leakage currents of 585 pA and 2.94 nA were achieved for the inverter and NOR gates, respectively.

“…However, that is difficult for a ring oscillator PUF because it requires measurement at several times to get frequency data once. Therefore, we began to investigate a buskeeper circuit 13,14) instead of the ring oscillator. In a previous study about thermal stability, we have reported that an organic buskeeper PUF keeps its ID value even after annealing for 25 h. 15) In this article, we expand the data on thermal stability up to 97 h and discuss a failure mode of an organic buskeeper PUF device.…”

Section: Introductionmentioning

confidence: 99%

Robustness of organic physically unclonable function with buskeeper circuit for flexible security devices

Kuribara

Watanabe

Takei

et al. 2022

Flexible devices have been studied to realize IoT or novel wearable devices. Data the flexible devices deal with can include personal information when application area expands more. A security system for flexible devices becomes more important in this case. In this study, we investigated thermal stability of an organic flexible security system. The security utilizes fabrication variation of a chip, and it is called physically unclonable function (PUF). As a result, bit error rate of an organic PUF was 1.8% and index of ID uniqueness (i.e., randomness) was almost theoretical value of 0.48. Generated ID remains even after annealing at 100°C for 97 hours by using CYTOP encapsulation. XRD measurement implies that a degradation of PUF characteristic partially derives from structure change of organic n-type semiconductor thin-film after annealing.