RSA Cryptosystem: Block Cipher or Stream Cipher

In the communication system, it is an important and essential concept that secret information must be kept secured. Cryptography is a branch of study that deals with message security. A public key cryptosystem RSA is an important mile stone in the field of message communication networks. In today’s modern computerized era where most of the messages are communicated through the internet, it is evident that messages are not in limited access between the sender and the receiver only. Third party, that is, any unauthorized person also may get access to the message communicated through any hostile communication channels like internet, telephone line etc. During the last five decades various types of cryptographic algorithms have emerged to protect the message from intruder. A new concept of public key cryptosystem was introduced by W. Diffie and M. E. Hellman in their revolutionary article. Following this concept, three eminent researchers at MIT Laboratory for Computer Science, Cambridge have designed the RSA algorithm which is the first public key cryptosystem. In this paper, a brief review on the RSA cryptosystem is presented.