Substitution plays a vital role in enhancing the security of symmetric block ciphers. Randomized substitution is more effective in triggering of confusion in symmetric block ciphers as compared to static substitution. Mostly the existing substitution methods used in Data Encryption Standard and in standardized Advanced Encryption Standard (AES) are static in nature. However, some efforts have been made in earlier years to replace the static S-box of AES with dynamic S-box, but all these dynamic substitution approaches are not truly random in nature. Thus, existing dynamic substitution methods are based on publically known substitution transformation and are not feasible for dynamically sized block ciphers, unlike the proposed substitution method. The proposed randomized substitution method (RSM) utilizes a pseudorandom-based direct association with a secret key without having any publicly known S-box transformation. Moreover, proposed RSM does not retain any irreducible polynomial {11B} in Galois field GF\((2^{8})\). The randomness properties of the proposed method have been evaluated through several well-known statistical tests with a standard tool (Statistical Testing Suite) recommended by the National Institute of Standard and Technology (NIST). Experimental results show that proposed RSM contains significant randomness properties which reflects the recommendations of NIST to be considered as a randomized substitution method.

替代在增强对称分组密码的安全性方面起着至关重要的作用。与静态替换相比，随机替换更有效地触发对称分组密码中的混淆。通常，数据加密标准和标准化高级加密标准（AES）中使用的现有替代方法本质上是静态的。然而，早些年已经做出了一些努力来用动态S-box替换AES的静态S-box，但是所有这些动态替换方法实际上并不是真正的随机方法。因此，与提出的替代方法不同，现有的动态替代方法基于公知的替代变换，并且对于动态大小的分组密码不可行。提出的随机替换方法（RSM）利用与伪密钥的基于伪随机的直接关联，而无需进行任何公知的S-box转换。此外，建议的RSM在Galois场GF中不保留任何不可约的多项式{11B}\（（（2 ^ {8}）\）。通过美国国家标准技术研究院（NIST）推荐的标准工具（统计测试套件），通过几种众所周知的统计测试，评估了所提出方法的随机性。实验结果表明，提出的RSM包含显着的随机性，这反映了NIST的建议，可将其视为随机替代方法。