Modified Blow Fish Algorithm
The paper, "Modified Blowfish Algorithm," by Theda Flare G. Quilala, Ariel M. Sison, and
Ruji P. Medina, published in the Indonesian Journal of Electrical Engineering and Computer
Science, explores a variant of the original Blowfish algorithm to enhance encryption
standards. The authors propose modifications that increase the block size and key length to
128 bits each, aiming to improve security and performance of cryptographic operations.
The original Blowfish algorithm, created by Bruce Schneier in 1994, is a symmetric block
cipher recognized for its speed and efficiency, particularly in environments with limited
resources. However, it uses a 64-bit block size, which raises concerns about potential
vulnerabilities such as shorter block sizes being more susceptible to certain types of attacks
like birthday attacks. The authors of the paper suggest that increasing the block size to 128
bits helps in minimizing the risk of duplicate blocks during encryption, which can leak
information.
In their approach, Quilala and her colleagues retained the basic structure of the original
Blowfish algorithm to ensure compatibility and ease of adoption but introduced significant
modifications. They reduced the number of S-boxes used from four to two and introduced a
derivation method that aims to increase the randomness in key generation and decrease
encryption symmetry. This derivation method also assists in achieving faster key setup times.
The modified Blowfish algorithm was subjected to various tests to assess its performance and
security enhancements. One key metric was encryption and decryption time. The results
showed that while the modified algorithm was slower than the original Blowfish—taking
longer for both encryption and decryption—it outperformed Twofish, another derivative of
Blowfish, in terms of speed. In terms of security, measured through the avalanche effect, the
modified algorithm showed a higher percentage change in output with a single bit change in
input, indicating better security characteristics than the original Blowfish.
The paper also detailed the technical aspects of the modifications. The key expansion
mechanism was revamped to accommodate a larger block size, with a streamlined subkey
generation process that reduces the memory footprint and enhances operational efficiency.
The P-array and S-boxes setup in the original Blowfish was altered in the modified version to
utilize the increased key and block sizes effectively.
In conclusion, the "Modified Blowfish Algorithm" paper proposes an innovative adaptation
of an established encryption algorithm to meet contemporary security standards while
maintaining a balance between performance and security. The proposed modifications not
only enhance the security features of the Blowfish algorithm but also address the challenges
posed by larger data block encryption in modern computing environments.