Randomized Substitution Method for Effectively Secure Block Ciphers in I.O.T Environment
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RESEARCH ARTICLE-COMPUTER ENGINEERING AND COMPUTER SCIENCE
Randomized Substitution Method for Effectively Secure Block Ciphers in I.O.T Environment Ijaz Ali Shoukat1 · Umer Iqbal1 · Abdul Rauf1 · Muhammad Rehan Faheem2 Received: 8 April 2020 / Accepted: 29 August 2020 © King Fahd University of Petroleum & Minerals 2020
Abstract 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(28 ). 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. Keywords Symmetric encryption · Dynamic substitution · Block cipher · Security · Privacy
1 Introduction Substitution methods are immensely crucial for symmetric cryptosystems. The Advanced Encryption Standard (AES) and Data Encryption Standard (DES) are noteworthy practices to handle data encryption in network communication. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13369-020-04919-3) contains supplementary material, which is available to authorized users.
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Umer Iqbal [email protected] Ijaz Ali Shoukat [email protected] Abdul Rauf [email protected] Muhammad Rehan Faheem [email protected]
1
Riphah College of Computing, Riphah International University Faisalabad Campus, Faisalabad, Pakistan
2
Department of Computer Science & IT, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
The current substitution policy (S-box design) of AES is static (fixed) and un-changeable upon secret key [1–3]. Therefore, the fixed or static design of AES-based substitution is its significant weakness because of static connection with input and output bits. This type of static connection does not establish a direct key-based association in AES substitution method. Having no straight-through
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