The benefit of using chaos in key schedule algorithm

Yousaf

Security and Communication Networks

et al. 2020

Key schedule algorithms play an important role in modern encryption algorithms, and their security is as crucial as the security of the encryption algorithms themselves. Many studies have been performed on the cryptographic strength evaluation of the encryption algorithms; however, strength evaluation of the key schedule algorithms often obtains less attention that can lead towards the possible loophole in the overall encryption process. In this paper, a criterion is proposed to evaluate the cryptographic strength of the key schedule algorithms. This criterion includes different methods of data generation from subkeys and a suitable set of statistical tests. The statistical tests are used to explore the cryptographic properties such as diffusion, confusion, independence, and randomness in the subkeys generated by the key schedule algorithm. The proposed criterion has been applied to some of the key schedule algorithms of different block ciphers. The results confirm that the proposed criterion can effectively differentiate between strong- and weak-key schedule algorithms.

Section: Introductionmentioning

confidence: 99%

Cryptographic Strength Evaluation of Key Schedule Algorithms

Yousaf

Security and Communication Networks

et al. 2020

“…Differential attacks are concerned with attacking the master secret key, where attackers try to find out whether a particular modification to the master key might lead to a specific difference in the key output of each round [12]. As demonstrated in Sections 4.7 and 4.8 through experimentation, a 1-bit change to the master secret key will get NBCR very close to the optimal value of 50%.…”

Section: Differential Attack Analysismentioning

confidence: 99%

“…In the literature, designing a strong and secure KEA has received less attention compared to encryption techniques [10], [11]. However, Harmouch and El Kouch [12] incorporated the concept of chaos into the key schedule (expansion) algorithm, resulting in the development of a new key scheduling method called CKSA, which is based on logic maps. This suggested algorithm is a one-way function that guarantees effective confusion and diffusion, as well as a good avalanche effect.…”

Section: Introductionmentioning

confidence: 99%

Unprecedented Security Analysis Results for a Novel Key Expansion Algorithm Based on Protein Sequences, Dynamic Mealy Machine, and 3D Logistic Map

2024

IJIES

The key expansion algorithm is an important part of any symmetric block cipher system since its effectiveness directly impacts the security of the entire block cipher; if it is not strong enough, the whole cryptosystem could be broken. Therefore, the round keys must be generated in a very secure way so that they cannot be attacked at all. Despite its great importance, cryptographic algorithm designers were not as interested in creating a secure round keys generation algorithm as they were in encryption itself. In this regard, designing a novel, simple, and flexible key expansion algorithm that generates round keys with secure characteristics is the aim of this research. The proposed Key Expansion algorithm is based on Dynamic Mealy Machine, 3D Logistic Map, and Protein Sequence (KE-DMM3DLMPS). The strength of the proposed KE-DMM3DLMPS algorithm is tested using flexibility, the NIST SP800-22 randomness test suite, histogram analysis, key space analysis, correlation coefficient, hamming distance, number of bit change rate, initial key sensitivity, confusion and diffusion, and differential attack. In comparison to some existing algorithms, experimental results showed that the generated round keys by the proposed KE-DMM3DLMPS algorithm passed all the NIST tests with higher randomness, a uniform and ideal distribution of the amino acids present in each round key, and a higher key space of up to 20 × 2 471 . Furthermore, the KE-DMM3DLMPS avoids the linear relationship between the master secret key and the generated round keys and is capable of effectively blocking differential attacks. The proposed algorithm successfully adheres to key cryptographic principles such as irreversibility, independence, the strict avalanche effect, confusion, and diffusion. Through comprehensive testing and comparisons, the derived conclusion asserts that our algorithm stands as an efficient and secure solution. Its applicability extends to any symmetric block cryptosystem, with the primary goal of enhancing encryption and bolstering security.

“…The KSA of AES was also improved by Shivani [34] by introducing three secret keys instead of one to increase the keyspace and overall system security. In addition, a highly efficient and independent KSA has been introduced, which uses chaos to generate round keys [35]. This research indicates that randomness, avalanche effect, the difference between round keys, and linear cryptanalysis are important security measures.…”

Section: Introductionmentioning

confidence: 99%

An Enhanced Key Schedule Algorithm of PRESENT-128 Block Cipher for Random and Non-Random Secret Keys

2022

The key schedule algorithm (KSA) is a crucial element of symmetric block ciphers with a direct security impact. Despite its undeniable significance, the KSA is still a less focused area in the design of an encryption algorithm. PRESENT is a symmetric lightweight block cipher that provides the optimal balance between security, performance, and minimal cost in IoT. However, the linear functions in KSA lead to a slow and predictable bit transition, indicating the relationship between round keys. A robust KSA should produce random and independent round keys irrespective of the secret key. Therefore, this research aims to improve the KSA PRESENT-128 block cipher with enhanced randomness, round key bit difference, and the avalanche effect. The experiments on round keys and ciphertext with random, low density and high-density secret key datasets endorse the expected improvements. Moreover, the results show that the improved KSA produces random round keys that successfully pass the NIST randomness test. The bit transition from one round key to another is increased from 20% to 40%, where a greater inclination of the avalanche effect has an increased effect with 50% bit change. On the other hand, the improved KSA PRESENT requires an additional 0.001871 s to generate round keys, as a security cost trade-off.