Abstract: “Now-a-days internet is one of the most important source of communication and thousands of people interact electronically. For sending sensitive messages over the internet, we need security. In this paper a security algorithm, Twofish has been explained with all of its modules with both 128 and 192-bit key size. Implementation on Xilinx – 6.1 xst software has been done taking delay as main constraint.”

Keywords: twofish, MDS, PHT, symmetric key, Function F and g.