Diffie-Hellman Key Exchange Modification using Blowfish Algorithm to Prevent Logjam Attack

Abstract

Diffie-Hellman Key Exchange promises secure connections using modulus computation. However, there is a flaw in its implementation which makes it vulnerable, especially to an attack called Logjam Attack. Therefore, a new key exchange algorithm was developed to prevent this attack. The proposed algorithm is the result of modified DiffieHellman Key Exchange using another algorithm, namely the Blowfish algorithm. Modifications that occur in the DiffieHellman Key Exchange are at the modulus computation, which were replaced by customized Blowfish encryption algorithm. The encryption process of the Blowfish algorithm used in the proposed algorithm used 136 XOR operations every 64-bits messages, which were about to be encrypted. The Diffie-Hellman modified algorithm was implemented into programs using Java programing language. The modified algorithm program has less memory usage and execution time than Diffie-Hellman Key Exchange program, which was tested. With the replacement of modulus computations with Blowfish encryption at the main process could make the modification algorithm immune to Logjam Attack. Therefore, the use of the modification algorithm is more secured than the one without modification.