Design and Implementation of Multi-key Blowfish and CAST Algorithm: Comparative Study with CBC, CFB and CTR Modes

Abstract

In modern communication systems, secret keys are used to secure sensitive information such as personal data, financial transactions and government secrets. However, the security of these systems is only as strong as the secrecy of the key utilized for encrypting and decrypting the data. The use of easy guessable or compromised keys can lead to unauthorized access, data breaches, and identity theft. Additionally, the distribution and management of secret keys present challenges such as key generation, key distribution, key revocation, and key renewal, which can be complex and costly. Therefore, finding secure and efficient methods to manage secret keys is crucial for ensuring the confidentiality, integrity, and availability of sensitive information in today's digital age. Therefore, to improve the security of the symmetric encryption algorithms, The new method to encrypt and decrypt the difference size files using multiple keys is proposed. In addition to investigate the impact of using multiple keys on the security and performance of symmetric algorithms. However, the multiple keys are generated previously using MD5 and SHA2. The chosen algorithms in this study are Blowfish and CAST, with chosen three modes of operation: CBC, CFB and CTR. The results presented in the paper demonstrated that the Blowfish algorithm with generated multiple keys outperforms in the CBC mode despite has the most encryption and decryption time-consuming and memory usage. Where the randomness of Blowfish with mode CBC and CTR is the best throughput then it follows Blowfish with mode CFB.

Keywords

• Cryptography, symmetric algorithms, Secret keys, Blowfish algorithm, CAST algorithm, Mode operation CBC, CTR,CFB.