Performance enhancement of Blowfish and CAST-128 algorithms and Security analysis of improved Blowfish algorithm using Avalanche effect

Summary: There has been a tremendous enhancement in the field of cryptography, which tries to manipulate the plaintext so that it becomes unreadable, less prone to hacker and crackers, and again obtain the plaintext back by manipulating this unreadable text in some way. In this regard, we have modified two secure algorithms Blowfish [1] and CAST-128 [5] which are secretkey block ciphers that enhance performance by modifying their function. We have shown that total time taken for encryption and decryption is reduced for both the algorithms after the modification. We have also made an attempt to show that this improvement will not violate the security when compared to that of existing Blowfish algorithm. For this purpose we have used avalanche effect [3] as the basis of security analysis. Because the change in the total time taken for encryption and decryption cannot be understood on software implementation, we have implemented VHDL application to show the differences in the delay.