Analysis of the security level of modified CBC algorithm cryptography using avalanche effect

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There have been many modifications of cryptographic algrotima aimed at increasing the security of the algorithm. One cryptographic algorithm that has been modified is CBC (Cipher Block Chaining) cryptography. CBC is a block-based modern cryptographic algorithm. The disadvantages that exist in CBC is the encryption process in each block plainteks using the same key, resulting in if the cryptanalyst finds the key that is used it will be easy to decrypt the ciphertext. Modifications made to CBC aimed at increasing security is by combining the Vigenere algorithm in determining the key and block transposition on the final reading of the encryption process. Parameters for assessing the algorithm are good or not by looking at the value of avalanche effect. A cryptographic algorithm will be categorized as good if the value of avalanche effect ranges between 45%-60% and bernilia is very good if the value of avalanche effect is 50%. The results of this study indicate that the modified CBC cryptographic algorithm resulting from the encryption process of several plaintexts has Avalanche effect values in the range above 50% and below 60%, which means that the modified CBC algorithm is of good value.