The internet today is being used by millions of users for a large variety of commercial and non commercial purposes. It is controlled by different entities. It is mainly used as an efficient means for communication, entertainment and education. With the rapid growth of internet, there is a need for protecting confidential data. The Internet was however originally designed for research and educational purpose, not for commercial applications.So internet was not designed with security in mind. As the internet grows the existing security framework was not adequate for modern day applications. Cryptography play a vital role in providing security.Lot of research is going on block cipher algorithms. In this paper we present a new 512 bit block cipher named SF Block cipher. The proposed cipher is developed based on design principle known as Substitution permutation network (SP Network). The algorithm is implemented in .NET Framework and MATLAB. Cryptanalysis is carried out in the encrypted file. It was found that the encrypted file with this algorithm is difficult to break.Simulation results shows that the proposed Block cipher has better performance over other algorithms such as AES and Blowfish

The growth rate of the internet exceeds than any other technology which is measured by users and bandwidth. Internet has been growing at a rapid rate since its conception, on a curve geometric and sometimes exponential. Today, the Internet is moving exponentially in three different directions such as size, processing power, and software sophistication making it the fastest growing technology humankind has ever created. With the rapid growth of internet, there is need to protect the sensitive data from unauthorized access. Cryptography plays a vital role in the field of network security. Currently many encryption algorithms are available to secure the data but these algorithms consume lot of computing resources such as battery and CPU time. This paper mainly focuses on two commonly used symmetric encryption algorithms such as Blowfish and Rejindael. These algorithms are compared and performance is evaluated. Experimental results are given to demonstrate the performance of these algorithms.