Randomised RC6 Algorithm with Python Implementation for Secure Email Communication

The RC6 cryptographic technique stands out as a key example of the importance of encryption, utilising advanced methods like key expansion and modular arithmetic to ensure data integrity and confidentiality. The technique is a symmetric key block cipher designed as an enhancement of RC5, operating on 128-bit data blocks with variable key sizes up to 256 bits. It uses modular additions, XOR operations, and data-dependent rotations over multiple rounds to ensure robust encryption. Known for its efficiency and strong security, RC6 remains a well-regarded cryptographic algorithm despite not being chosen as the AES standard. A distinctive aspect of RC6 is its use of integer multiplication, which provides an additional level of diffusion (mixing of the input data) compared to RC5. This paper develops a modified version of the RC6 by randomising its diffusion process. The modified algorithm is developed in Python scripts to encrypt text messages before they are sent via email and to decrypt the transmitted data, enabling secure communication. This paper provides a practical solution for protecting sensitive information shared via email, contributing to the advancement of secure communication practices in the digital era.