Security analysis and enhancement of a cryptosystem based on phase truncation and a designed amplitude modulator

Xiong Y.; He A.; Quan C.

摘要

In this paper, the security of a cryptosystem based on phase truncation and a designed amplitude modulator (AM) is evaluated. In the cryptosystem, an undercover AM used as an additional key is added to modulate the amplitude information of the spectrum in the Fourier plane. Compared to the conventional phase-truncated Fourier transform (PTFT)-based cryptosystem, the security of the cryptosystem is improved by increasing the number of unknown keys. However, it is found that the designed AM is irrelative to the plaintext, and one of the parameters in the designed AM contributes less to the security enhancement of the cryptosystem due to low key sensitivity. Based on the analysis, a special attack containing two iterative processes is proposed to crack the cryptosystem, in which the known-plaintext-attack-based iterative process I with a specific normalization operator is used to retrieve the designed AM and the amplitude-phase-retrieval-technique-based iterative process II is used to retrieve the corresponding plaintext from the arbitrarily given ciphertext with the help of the retrieved AM. In addition, an inherent drawback widely existing in PTFT-based cryptosystems is reported for the first time: most information of the original image could be retrieved using two correct phase keys (or only the first phase key) generated in the encryption process, even without the corresponding ciphertext in PTFT-based cryptosystems. To address this issue, a security-enhanced cryptosystem is proposed in this paper. Numerical simulation is carried out to demonstrate the effectiveness and feasibility of the proposed attack and cryptosystem. (C) 2019 Optical Society of America

机译：在本文中，评估基于阶段截断的密码系统和设计的幅度调制器（AM）的安全性。在密码系统中，添加底层用作附加密钥以调制傅里叶平面中频谱的幅度信息。与传统的相位截断的傅立叶变换（PTFT）基础的密码系统相比，通过增加未知键的数量来提高密码系统的安全性。然而，发现设计的AM是对明文的，并且设计的一个参数之一由于低调敏感性而导致密码系统的安全增强。基于分析，建议包含两个迭代过程的特殊攻击来破解密码系统，其中使用特定归一化运算符的已知宣言攻击的迭代过程I用于检索设计的AM和幅度阶段 - 基于检索技术的迭代过程II用于从检索到的AM的帮助下从任意给定的密文中检索相应的明文。此外，首次报告了基于PTFT的密码系统中广泛存在的固有缺点：即使没有基于PTFT的密码系统中的相应密文。要解决此问题，本文提出了一种安全增强密码系统。进行了数值模拟，以证明所提出的攻击和密码系统的有效性和可行性。（c）2019年光学学会

Security analysis and enhancement of a cryptosystem based on phase truncation and a designed amplitude modulator

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