Date of Publication :28th September 2023

Abstract: This study aimed to improve the security of the Beaufort Cipher Expansion Technique by addressing the cipher's vulnerabilities to Kasiski attacks, brute force attacks, and frequency analysis attacks. The research objectives include modifying the key-generation process and the key-encryption process and improving the matrix to mitigate these vulnerabilities. The analysis of the Kasiski attack revealed that the enhanced Beaufort Cipher Expansion Technique showed no pattern in the generated ciphertext, unlike the traditional Beaufort Cipher, which exhibited a trigram pattern. The result indicates that the enhanced technique effectively addressed the vulnerability to pattern recognition attacks. Also, the brute force attack analysis showed that it would take about 3.83376E+17 centuries to break a 10-letter ciphertext. The result indicates that the enhanced Beaufort cipher is strong against brute-force attacks. Regarding frequency analysis, the original Beaufort Cipher Expansion Technique resulted in a ciphertext with frequent occurrences of specific values, making it susceptible to such an attack. In contrast, the enhanced technique distributed characters evenly, making it more secure and challenging for attackers to extract meaningful information through frequency analysis. Furthermore, the avalanche effect analysis compared the enhanced Beaufort cipher expansion technique with other relevant studies, and it achieved an avalanche effect of 51.66%, surpassing the desired value of 50%. The results indicate that determining which bits of the original message change when altering a random bit becomes challenging, thus further enhancing the cipher's security. Overall, the findings demonstrated that the enhanced Beaufort Cipher Expansion Technique effectively addressed the vulnerabilities to the Kasiski attack, brute force attack, and frequency analysis attack. The modifications improved the security and robustness of the cipher, making it a valuable contribution to the field of cryptography.

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