Biblio
We consider some approaches to the construction of lightweight block ciphers and introduce the definitions for "index of strong nonlinearity" and "index of perfection". For PRESENT, MIDORI, SKINNY, CLEFIA, LILLIPUT mixing and nonlinear properties were evaluated. We obtain the exact values of the exponents for mixing matrices of round functions and the upper bounds for indexes of perfection and strong nonlinearity. It was determined by the experiment that each coordinate function of output block is nonlinear during 500 rounds. We propose the algorithmic realization of 16×16 S-box based on the modified additive generator with lightweight cipher SPECK as a modification which does not demand memory for storage huge substitution tables. The best value of the differential characteristic of such S-box is 18/216, the minimal nonlinearity degree of coordinate functions is equal to 15 and the minimal linear characteristic is 788/215.
Radio Frequency Identification (RFID) systems are widely used today because of their low price, usability and being wireless. As RFID systems use wireless communication, they may encounter challenging security problems. Several lightweight encryption algorithms have been proposed so far to solve these problems. The RBS block cipher is one of these algorithms. In designing RBS, conventional block cipher elements such as S-box and P-box are not used. RBS is based on inserting redundant bits between altered plaintext bits using an encryption key Kenc. In this paper, considering not having a proper diffusion as the main defect of RBS, we propose a chosen ciphertext attack against this algorithm. The data complexity of this attack equals to N pairs of text and its time complexity equals to N decryptions, where N is the size of the encryption key Kenc.
In order to provide secure data communication in present cyber space world, a stronger encryption technique becomes a necessity that can help people to protect their sensitive information from cryptanalyst. This paper proposes a novel symmetric block cipher algorithm that uses multiple access circular queues (MACQs) of variable lengths for diffusion of information to a greater extent. The keys are randomly generated and will be of variable lengths depending upon the size of each MACQ.A number of iterations of circular rotations, swapping of elements and XORing the key with queue elements are performed on each MACQ. S-box is used so that the relationship between the key and the cipher text remains indeterminate or obscure. These operations together will help in transforming the cipher into a much more complex and secure block cipher. This paper attempt to propose an encryption algorithm that is secure and fast.