A Modified Hill Cipher Based on Circulant Matrices

Secured communication of text information is prime importance across the globe. Cryptography is one of the methods to attain security. The Hill cipher is a symmetric encryption algorithm vulnerable to the attack of knownplaintext. This paper proposes a modification to the Hill cipher. In the proposed cryptosystem, a prime circulant matrix is shared as a secret key and a non-singular matrix G is used as a public key such that the determinant of coefficient matrix Gc is zero. Which generates infinite solutions. This makes difficulty to find secret key matrix.