Random S-boxes Research Articles

A Chaos-Based Authenticated Cipher with Associated Data

In recent years, there has been a rising interest in authenticated encryption with associated data (AEAD) which combines encryption and authentication into a unified scheme. AEAD schemes provide authentication for a message that is divided into two parts: associated data which is not encrypted and the plaintext which is encrypted. However, there is a lack of chaos-based AEAD schemes in recent literature. This paper introduces a new 128-bit chaos-based AEAD scheme based on the single-key Even-Mansour and Type-II generalized Feistel structure. The proposed scheme provides both privacy and authentication in a single-pass using only one 128-bit secret key. The chaotic tent map is used to generate whitening keys for the Even-Mansour construction, round keys, and random s-boxes for the Feistel round function. In addition, the proposed AEAD scheme can be implemented with true random number generators to map a message to multiple possible ciphertexts in a nondeterministic manner. Security and statistical evaluation indicate that the proposed scheme is highly secure for both the ciphertext and the authentication tag. Furthermore, it has multiple advantages over AES-GCM which is the current standard for authenticated encryption.

Study of Randomness in AES Ciphertexts Produced by Randomly Generated S-Boxes and S-Boxes with Various Modulus and Additive Constant Polynomials

In Advanced Encryption Standard (AES), the standard S-Box is conventionally generated by using a particular irreducible polynomial {11B} in GF(28) as the modulus and a particular additive constant polynomial {63} in GF(2), though it can be generated by many other polynomials. In this paper, it has been shown that it is possible to generate secured AES S-Boxes by using some other selected modulus and additive polynomials and also can be generated randomly, using a PRNG like BBS. A comparative study has been made on the randomness of corresponding AES ciphertexts generated, using these S-Boxes, by the NIST Test Suite coded for this paper. It has been found that besides using the standard one, other moduli and additive constants are also able to generate equally or better random ciphertexts; the same is true for random S-Boxes also. As these new types of S-Boxes are user-defined, hence unknown, they are able to prevent linear and differential cryptanalysis. Moreover, they act as additional key-inputs to AES, thus increasing the key-space.

Encryption using Dual Key Transformation based on Creation of Multi S- Boxes in AES Algorithm

The Advanced Encryption Standard (AES) is using in a large scale of applications that need to protect their data and information. A nonlinear substitution operation is the main factor of the AES cipher system strength. The S-Box component that used in AES is fixed, and not changeable. The purpose of the proposed approach is to use dual keys in encryption and decryption processes in SubByte transformation function. The first key generate multi random S-boxes depend on using multi keys that led to generate Sboxes provided that each one has its inverse associated with it, the second key is a random distribution of the S-boxes, the dual keys lead in increasing the complexity degree within the same delay time during the encryption and decryption processes in SubByte function. The results show that the present proposed algorithm has good cryptographic strength, with the added benefit that is resistant to linear and differential cryptanalysis, which require that the S-boxes be known beside the encryption key. General Terms Security, Algorithms, system strength, Plaintext, Ciphertext

Comparison of random S-box generation methods

Random bijective S-box generation methods are considered. An alternative S-box generation method by forming compositions of permutations from some fixed set is proposed. Experiments show that the rate of acceptable S-boxes for all the methods considered is essentially the same. The advantage of the composition method is an obvious parametrization, with the potentially large key space.

Key-Dependent S-Box Generation in AES Block Cipher System

Advanced Encryption Standard (AES) block cipher system is widely used in cryptographic applications. A nonlinear substitution operation is the main factor of the AES cipher system strength. The purpose of the proposed approach is to generate the random S-boxes changing for every change of the secret key. The fact that the S-boxes are randomly key-dependent and unknown is the main strength of the new approach, since both linear and differential cryptanalysis require known S-boxes. In the paper, we briefly analyze the AES algorithm, substitution S-boxes, linear and differential cryptanalysis, and describe a randomly key-dependent S-box and inverse S-box generation algorithm. After that, we introduce the independency measure of the S-box elements, and experimentally investigate the quality of the generated S-boxes.