File encryption using Fisher-Yates Shuffle

A permutation cipher is a very old form of cryptography. It works by moving letters around in a random pattern. In this paper we have implemented a new method of pseudorandom permutation. Along with this, a working algorithm has been provided that produces a block cipher using the mentioned procedure. The discussed algorithm operates on a file containing a stream of integers delimited by a space. The file is first converted to a two dimensional array. This array is randomly shuffled. Thereafter the encrypted cipher is obtained by recombining the keys with the shuffled array. For decryption, the cipher is again read into a two dimensional array. This time, the entire array is sub-divided into three parts. The first and the final part consist of the shuffled message. The second part consists of the keys. The elements of the shuffled array are then rearranged in accordance to the keys. The recombination results in retrieving the original file containing the stream of integers.