Structural Cryptanalysis of the Message Based Random Variable Length Key Encryption Algorithm (MRVLK)

This article has presented a Structural cryptanalysis on MRVLK (Message Based Random Variable Length Key Encryption). In this cipher, key length is started from small amount of bits and then will be grown in size. The cipher has variable rounds, random bitwise rotations and dynamic key length that provide resistance to linear and differential cryptanalysis. In spite of these advantages, some disadvantages are observed such as correlation between the ciphertexts in each stage which facilitates structural attack. Even random mechanism such as S-box in this cipher cannot prevent this attack. The attack performs analysis on the final ciphertext and reveals the plaintext of MRVLK by exploiting the fact that the structure of the ciphertext is obvious and weak. The presented attack efficiently utilizes this information and prompts the operations cryptanalysis. Performance of this attack is evaluated in terms of running time. The results show that the original plaintext is achievable to minimal cost.