缩减轮GRANULE算法的中间相遇分析

Meet-in-the-Middle Attacks on Reduced-Round GRANULE

摘要: 轻量级分组密码是为计算资源受限的环境而设计的加密算法。它具有计算开销小、占用存储空间少、能耗低等优点，广泛用于嵌入式系统、智能卡以及物联网等应用场景。然而，为了追求更高的实现效率，设计轻量级分组密码算法时会牺牲部分安全性，所以有必要评估它的安全强度。本文利用中间相遇分析法对轻量级分组密码GRANULE算法的安全性进行了评估。首先，构造了7轮的GRANULE的中间相遇区分器，随后在它的前面接4轮、后面接3轮，构建了14轮的GRANULE中间相遇分析的攻击路径，并在结合GRANULE的轮密钥之间的一些线性关系之后，最终攻击需要的数据复杂度为2⁶⁰选择明文，时间复杂度为2^111.2次14轮GRANULE加密，存储复杂度为2^104.9个64比特块。此结果是对GRANULE安全性分析的有效补充，攻击结果表明GRANULE能较好地抵抗中间相遇攻击。

Abstract: Lightweight block cipher is an encryption algorithm designed for environments with limited computing resources. It has the advantages of low computational cost, less storage space occupation, and low energy consumption, and is widely used in application scenarios such as embedded systems, smart cards, and the Internet of Things. However, in order to pursue higher implementation efficiency, designing lightweight block cipher algorithms may sacrifice some security, so it is necessary to evaluate its security strength. In this article we evaluate the security of the lightweight block cipher GRANULE algorithm using the intermediate encounter analysis method. Firstly, a 7-round GRANULE intermediate encounter discriminator was constructed, followed by 4 rounds in front and 3 rounds behind it. 14-round GRANULE intermediate encounter analysis attack path was constructed, and after combining some linear relationships between GRANULE’s round keys. Data complexity is 2⁶⁰ chosen plaintexts, time complexity is 2^111.2 14-round GRANULE encryption, and storage complexity is 2^104.9 64-bit blocks. This result is an effective supplement to the security analysis of GRANULE, and the attack results indicate that GRANULE can resist intermediate encounter attacks well.