Physical unclonable functions (PUFs) are hardware security primitives that are used for device authentication and cryptographic key generation. Standard XOR PUFs typically contain multiple standard arbiter PUFs as components, and are more secure than standard arbiter PUFs or feed-forward (FF) arbiter PUFs (FF PUFs). This paper proposes design of feed-forward XOR PUFs (FFXOR PUFs) where each component PUF is a FF PUF. Various homogeneous and heterogeneous FFXOR PUFs are presented and evaluated in terms of four fundamental properties of PUFs: uniqueness, attack-resistance, reliability and randomness. Certain key issues pertaining to XOR PUFs such as their vulnerability to machine learning attacks and instability in responses are investigated. Other important challenges like the lack of uniqueness in FF PUFs and the asymmetry in FPGA arbiter PUFs are addressed and it is shown that FFXOR PUFs can naturally overcome these problems. It is shown that heterogeneous FFXOR PUFs (i.e., FFXOR PUFs with non-identical components) can be resilient to state-of-the-art machine learning attacks. We also present systematic reliability analysis of FFXOR PUFs and demonstrate that soft-response thresholding can be used as an effective countermeasure to overcome the degraded reliability bottleneck. Observations from simulations are further verified through hardware implementation of 64-bit FFXOR PUFs on Xilinx Artix-7 FPGA.

中文翻译：

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同质和异质前馈异或物理不可克隆函数


物理不可克隆函数 (PUF) 是用于设备身份验证和加密密钥生成的硬件安全原语。标准XOR PUF通常包含多个标准仲裁器PUF作为组件，并且比标准仲裁器PUF或前馈(FF)仲裁器PUF (FF PUF)更安全。本文提出了前馈 XOR PUF (FFXOR PUF) 的设计，其中每个分量 PUF 都是 FF PUF。根据 PUF 的四个基本属性：唯一性、抗攻击性、可靠性和随机性，提出并评估了各种同质和异构 FFXOR PUF。研究了与 XOR PUF 相关的某些关键问题，例如易受机器学习攻击的脆弱性和响应的不稳定。解决了其他重要挑战，例如 FF PUF 缺乏唯一性和 FPGA 仲裁器 PUF 不对称性，并且结果表明 FFXOR PUF 可以自然地克服这些问题。结果表明，异构 FFXOR PUF（即具有不同组件的 FFXOR PUF）可以抵御最先进的机器学习攻击。我们还提出了 FFXOR PUF 的系统可靠性分析，并证明软响应阈值可以用作克服可靠性下降瓶颈的有效对策。通过 Xilinx Artix-7 FPGA 上 64 位 FFXOR PUF 的硬件实现，进一步验证了仿真观察结果。