This paper introduces an Improved RC6 (IRC6) cipher for data encryption based on data-dependent rotations. The proposed scheme is designed with the potential of meeting the needs of the Advanced Encryption Standard (AES). Four parameters are used to characterize the proposed scheme. These parameters are the size of the word (w) in bits, the number of rounds (r), the length of the secret key (b) in bytes, and the size of the block (L) in bits. The main feature of IRC6 is the variable number of

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... rking registers instead of just four registers as in RC6, resulting in a variable block size for plaintext and ciphertext. The IRC6 cipher is designed to improve the robustness against attacks by increasing the diffusion for each round and providing greater security with fewer rounds. The effectiveness of the proposed IRC6 scheme is verified against theoretical attacks. The proposed IRC6 scheme depends on full diffusion and confusion mechanisms regardless of the utilized block size. The proposed IRC6 scheme saves 70% of the encryption time and 64% of the decryption time of RC6. The simulation results prove that the IRC6 achieves a better encryption/decryption time compared to the traditional RC6. Therefore, the proposed IRC6 is anticipated to fulfill the market needs and system security requirements.