An Implementation of the Blowfish Cryptosystem

The Blowfish cryptosystem is a very fast and useful scheme, even though it was introduced over a decade ago. This cryptosystem consists of two parts, a subkey and S-box generation phase, and an encrypiton phase. A short introduction to both algorithms are given, along with a few notes about the Ciphertext Block Chaining (CBC) mode. Some general information about attacks are explained, along with information about some of the people who have worked to analyze and attempt to break Blowfish. An implementation of a Windows tool for encrypting files which uses Blowfish is also examined in this paper. The results of the encryption tool clearly demonstrate how fast the encryption is compared to the subkey and S-box generation. The secrecy of the cryptosystem is explained by using several test files of different types, as well as a study of the security with respect to the number of rounds. Finally, some possible extensions to the software tool to improve its usefulness based on the strength of Blowfish are given.