Extended Hill Cipher Decryption by Using Transposed Interweaved Shifting

This paper is discussed about the strength of extended cipher due to non-linear transformation of interweave transposition and shifting operations. The impact of number of iterations on the avalanche effect is investigated. During encryption process the interweaving of the resulting plaintext, at each stage of the iteration, and the multiplication with the key matrix followed by transposition and shifting leads to confusion and diffusion. While decryption of the cipher text obtained after encryption process makes the use of reverse shifting and inverse transposed interweaving . From the cryptanalysis performed in this investigation, we have found that the cipher is a strong one. Here we propose Hill cipher modifications using Transposed Interweaved Shifting with significantly less computational complexity. The proposed modifications decrease encryption time while keeping the strength of the ciphers . It has been found that the extended algorithm takes less execution time when compared with DES and is more efficient in terms of execution.