Privacy protection of biometric traits using modified hill cipher with involutory key and robust cryptosystem

In this paper we have proposed a technique for securing biometric traits using the modified Hill Cipher with an involutory key and a robust cryptosystem. The Modified Hill Cipher solves the drawbacks of conventional Hill ciphers by using iterations and interlacing. Interlacing of the binary bits of the plaintext image creates confusion while iterations create complexity to the cipher image. The Modified Hill cipher is secure to known plaintext. Binary conversion is only possible for integer elements so an integer involutory key matrix is used. As the key matrix is involutory, which eliminates necessity of matrix inverse while decryption. We have used a robust cryptosystem algorithm to send the cipher matrix safely. The cryptanalysis and histogram graphs show the variation of image property before and after encryption.