Cipher

About: Cipher is a research topic. Over the lifetime, 9409 publications have been published within this topic receiving 110309 citations. The topic is also known as: cypher & cryptographic algorithm.

Key-Alternating Ciphers in a Provable Setting: Encryption Using A Small Number of Public Permutations

Abstract: This paper considers—for the first time—the concept of keyalternating ciphers in a provable security setting. Key-alternating ciphers can be seen as a generalization of a construction proposed by Even and Mansour in 1991. This construction builds a block cipher PX from an n-bit permutation P and two n-bit keys k0 and k1, setting PXk0,k1(x) = k1 ⊕ P (x ⊕ k0). Here we consider a (natural) extension of the EvenMansour construction with t permutations P1, . . . , Pt and t + 1 keys, k0, . . . , kt. We demonstrate in a formal model that such a cipher is secure in the sense that an attacker needs to make at least 2 queries to the underlying permutations to be able to distinguish the construction from random. We argue further that the bound is tight for t = 2 but there is a gap in the bounds for t > 2, which is left as an open and interesting problem. Additionally, in terms of statistical attacks, we show that the distribution of Fourier coefficients for the cipher over all keys is close to ideal. Lastly, we define a practical instance of the construction with t = 2 using AES referred to as AES. Any attack on AES with complexity below 2 will have to make use of AES with a fixed known key in a non-black box manner. However, we conjecture its security is 2.

A novel image cipher based on mixed transformed logistic maps

Abstract: In this paper, a novel secure cryptosystem is proposed for direct encryption of color images, based on transformed logistic maps. The proposed cipher provides good confusion and diffusion properties that ensures extremely high security due to the mixing of colors pixels. The encryption scheme makes use of six odd secret keys and chaotic keys for each operation. The operations include initial permutation of all pixels with six odd keys, nonlinear diffusion using first chaotic key, xoring the second chaotic key with resultant values and zig-zag diffusion with third chaotic key. The proposed scheme supports key sizes ranging from 192 to 400 bits. The security and performance of the proposed image encryption technique have been analysed thoroughly using statistical analysis, key sensitivity analysis, differential analysis, key space analysis, entropy analysis and performance analysis. Results of the various types of analyses are showing that the proposed image encryption technique is more secure and fast and hence suitable for the real-time applications.

The FEAL Cipher Family

Abstract: FEAL-8 has been expanded to FEAL-N (N round FEAL with 64-bit key), where FEAL-N with N=4/8 is identical to FEAL-4/-8 which have been previously published respectively. N is a user defined parameter (N≥4, N:even, N=2x, 2 ≥2 is recommended). FEAL-N has also been expanded to FEAL-NX (X: expansion, N round FEAL with 12-bit key) that accepts 128-bit keys. When the right half of the 128-bit key is all zeros, FEAL-NX works as FEAL-N. Upward compatibility is an important concept of the FEAL cipher family [1].