Abstract:
Information security is an important issue. Hill Cipher is one of the most famous symmetric cryptosystem that can be used to protect information from unauthorized
access.Hill cipher is a polygraph substitution cipher based on linear algebra. Invented by Lester S. Hill in 1929, it was the first polygraph cipher which was practical to
operate on more than three symbols at once, Hill Cipher has many advantages in data encryption. First, it is resistant to the frequency letter analysis. It's also very
simple since it uses matrix multiplication. Finally, it has high speed and high throughput [1,13,14], However, non-invertible key matrix over is the main disadvantage of Hill Cipher, because few of the matrices have inverses over . This means that the encrypted text can't be decrypted [2]. This paper suggests a new technique in Hill Cipher algorithm to overcome its major problem non-invertible key matrix. also our paper suggest
enhancement the security of Hill Cipher against known plaintext attack because all steps in Hill Cipher depend on linear algebra calculation This is possible by using public
key idea and key generating depending on various options and without linear algebra steps. Therefore, it will be difficult for the attacker to get the key. Finally, our paper
will present a proper solution for the problem of sending secret key (SK) for the first time. Our idea is using a public key public (PK) that doesn't sent but generated in the
encryption and decryption sides.
