In physically unclonable functions (PUFs), generating random cryptographs is required to secure private information. Various memory-based PUFs (MemPUFs), where cryptographs are generated independently from each PUF cell to increase the unpredictability of the cryptographs, have been proposed. Among them, the spin-transfer torque magnetic random-access memory MemPUF generates constant responses under temperature and voltage variations by exploiting a magnetic tunnel junction (MTJ) as the variation source. However, its response stability is diminished by the different characteristics of the two access transistors used in a PUF cell. To solve this problem, a novel PUF array that employs a diode-connected transistor and a shared access transistor, is proposed. In addition, a two-step postprocessing is adopted: 1) a write-back technique that amplifies the initial mismatch of MTJ resistances, and 2) a cell-classification technique that detects unstable PUF cells and discards their responses. The Monte Carlo HSPICE simulation results using industry-compatible 65-nm technology show that the proposed PUF system achieves the highest independence (autocorrelation factor of 0.0306) and the lowest maximum bit error rate (BER) under temperature and supply-voltage variations (<0.01% and 0.04% in the ranges of −25 to 75 °C and 0.8–1.2 V, respectively) compared with conventional PUF systems that exploit independent variation sources.

中文翻译：

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使用二极管连接的晶体管和两步后处理的基于MTJ的高度独立的PUF系统，以提高响应稳定性

在物理上不可克隆的功能（PUF）中，需要生成随机密码来保护私人信息。已经提出了各种基于存储器的PUF（MemPUF），其中，与每个PUF单元独立地生成密码，以增加密码的不可预测性。其中，自旋传递转矩磁性随机存取存储器MemPUF通过利用磁性隧道结（MTJ）作为变化源在温度和电压变化下产生恒定响应。但是，PUF单元中使用的两个访问晶体管的不同特性会降低其响应稳定性。为了解决这个问题，提出了一种新颖的采用二极管连接的晶体管和共享存取晶体管的PUF阵列。另外，采用了两步后处理：1）一种写回技术，可放大MTJ电阻的初始失配，以及2）一种细胞分类技术，可检测不稳定的PUF细胞并丢弃其响应。使用行业兼容的65纳米技术进行的Monte Carlo HSPICE仿真结果表明，在温度和电源电压变化（<0.01）的情况下，拟议的PUF系统实现了最高的独立性（自相关因子为0.0306）和最低的最大误码率（BER）。与采用独立变化源的传统PUF系统相比，分别在−25至75°C和0.8–1.2 V的范围内分别提高了％和0.04％。