A Novel Binary Hybrid PSO-EO Algorithm for Cryptanalysis of Internal State of RC4 Cipher

Area of Science:

• Computer Science
• Cryptography
• Optimization Algorithms

Background:

• Cryptography is essential for privacy and confidentiality, necessitating secure, cryptanalysis-resistant ciphers.
• The RC4 stream cipher is widely used but vulnerable to attacks.
• Global optimization techniques are increasingly hybridized to enhance problem-solving capabilities.

Purpose of the Study:

• To reveal a new state recovery attack against the RC4 stream cipher.
• To propose a hybrid optimization algorithm for cryptanalysis.
• To evaluate the effectiveness of the proposed method against RC4.

Main Methods:

• A plaintext attack was employed, leveraging known plaintext and ciphertext to derive the keystream and internal state.
• A hybrid Particle Swarm Optimization and Evolutionary Optimization (PSOEO) algorithm was developed and converted to its binary form (HBPSOEO).
• A novel fitness function was designed for the HBPSOEO algorithm to target RC4's internal state.

Main Results:

• The HBPSOEO algorithm demonstrated superior accuracy and speed in cryptanalyzing the RC4 cipher compared to using PSO or EO independently.
• The proposed method successfully identified RC4's internal state by examining only 10^4 possibilities.
• This represents a significant reduction compared to the 2^128 states required for brute-force attacks.

Conclusions:

• The developed HBPSOEO algorithm offers an efficient and effective method for cryptanalyzing the RC4 stream cipher.
• This research highlights the vulnerability of RC4 to state recovery attacks using advanced optimization techniques.
• The findings contribute to the ongoing effort to develop more secure cryptographic systems.