ABSTRACT

Online communication is one of the common means of communication in this era of globe village. As the number of people being connected to online communication system through their mobile phone, computer or any other e-communication tools increases, there is need to secure the communication networks from adversaries (third parties) between the sender and receivers. There are many aspects to security approach in online communication environment. One essential aspect for secure communications is that of cryptography, which is the focus of this research. This research work aims at designing and implementing cryptosystem using a simple polyalphabetic cipher algorithm. The algorithm was coded with Java programming language. It was discovered that cryptography system with polyalphabetic cipher algorithm is better compared to Atbash cipher, Scytale cipher, Ceasar cipher etc, because it is very difficult for adversaries to decrypt an encrypted data without the key.

Keywords: - Cryptography, Cryptosystem, Decrypt data, e-communication, Encrypted data, Java programming language, online communication, Polyalphabetic cipher algorithm