QMail: Hybrid Quantum Secure Email Client Application

The emergence of commercial quantum computers is inevitable and only a matter of time given the rapid progress made by companies such as IBM, Google, and Microsoft. Commercialization of quantum computers threatens cur-rent encryption methods that have worked effectively up until now however, with the advent of Shor’s and Grover's algorithms (quantum algorithms) for breaking current encryption methods, this compromises confidentiality, integrity and au-thenticity. Securing communication channels must be a top priority, and since email is the most widely used communication method, it must be addressed first. QMail, a Quantum Secure Email Client Application (QSECA), is designed to withstand both classical and quantum-level attacks. It uses a hybrid architecture of both Quantum Key Distribution (QKD) for the session key (simulated) and Post-Quantum Cryptography (PQC) for authentication and metadata protection, innovating on top of existing QSECA. The prototype we have made features a user-friendly interface to choose between three levels of encryption, including OTP. Our results indicate that QMail supports end-to-end security and offers pro-tection against adversaries with quantum capabilities, within the scope of the sce-narios tested. We have established QMail as a foundation for a quantum-safe communication platform - a step towards secure communication in the era of 6G and quantum internet with scalability as a direction for future work.