TRANSPOLY HILL CIPHER -- AN IMPROVEMENT OVER TRADITIONAL HILL CIPHER.

Every encryption technique is based on any one of two facts-substitution or transposition. Sometimes the combination of both techniques is used. Substitution technique is based on replacement of given plaintext letters by other letters or symbols to get the ciphertext. The basic concept behind this paper is to improve the strength of Hill cipher, 'a multiple-letter substitution cipher' against known plaintext attack. This paper presents a modified approach which is an enhancement over traditional Hill cipher by using symmetric matrix of plaintext letters. [ABSTRACT FROM AUTHOR]