Abstract The rise of quantum computing challenges the fundamental security of classical public-key cryptography, exposing email systems to harvest-now-decrypt-later (HNDL) attacks demanding the need for practical post-quantum solutions. We present QSecureMail, a quantum-key-distribution (QKD) supported email client featuring an Adaptive Security Policy Engine (ASPE) which dynamically selects encryption levels based on real-time key pool conditions. The system integrates ETSI GS QKD 014 infrastructure and incorporates a Hybrid QKD⊕PQC scheme (Level 3) that combines ML-KEM1024 (FIPS 203) with QKD-derived keys, along with an authenticated QKD-based one-time pad construction (Level 1). It also introduces a structured security attestation mechanism that enables transparent auditing of the security posture of each email. A reference implementation and evaluation show that the ASPE effectively manages key consumption across different security levels while maintaining practical performance. Overall, the results indicate that QSecureMail offers a feasible approach to deploying quantum-safe email over existing infrastructure.
Abstract The rise of quantum computing challenges the fundamental security of classical public-key cryptography, exposing email systems to harvest-now-decrypt-later (HNDL) attacks demanding the need for practical post-quantum solutions. We present QSecureMail, a quantum-key-distribution (QKD) supported email client featuring an Adaptive Security Policy Engine (ASPE) which dynamically selects encryption levels based on real-time key pool conditions. The system integrates ETSI GS QKD 014 infrastructure and incorporates a Hybrid QKD⊕PQC scheme (Level 3) that combines ML-KEM1024 (FIPS 203) with QKD-derived keys, along with an authenticated QKD-based one-time pad construction (Level 1). It also introduces a structured security attestation mechanism that enables transparent auditing of the security posture of each email. A reference implementation and evaluation show that the ASPE effectively manages key consumption across different security levels while maintaining practical performance. Overall, the results indicate that QSecureMail offers a feasible approach to deploying quantum-safe email over existing infrastructure.
The emergence of quantum computing poses a significant threat to classical cryptographic mechanisms such as RSA and Elliptic Curve Cryptography that are widely used to secure email communication. Traditional secure email systems rely on classical public-key infrastructure and therefore lack resilience against quantum attacks. This paper presents QuMail, a quantum-secure email client that integrates BB84-based Quantum Key Distribution (QKD) simulation, CRYSTALS-Kyber post-quantum cryptography (PQC), and blockchain-based audit logging within a unified architecture. The proposed system operates entirely at the application layer and remains compatible with existing email infrastructures using standard SMTP and IMAP protocols without requiring any server-side modification. A modular prototype was implemented using IBM Qiskit for quantum key generation and hybrid cryptographic techniques for secure message transmission. Experimental evaluation demonstrates an average latency of 120–180 ms for QKD key generation and 20–30 ms for Kyber-based encryption while maintaining minimal overhead for email transmission. The results demonstrate the feasibility of integrating quantum-resilient security mechanisms into existing email systems and highlight the potential of hybrid QKD–PQC architectures for next-generation secure communication platforms.
The advent of quantum computing threatens classical cryptographic mechanisms, demanding new strategies for securing communication networks. Since real-world networks cannot be fully Quantum Key Distribution (QKD)-enabled due to infrastructure constraints, practical security solutions must support hybrid operation. This paper presents an adaptive security framework that enables quantum-safe communications across real-world heterogeneous networks by combining QKD and Post-Quantum Cryptography (PQC). Building upon a hierarchical key management architecture with Virtual Key Management Systems (vKMS) and a centralized Quantum Security Controller (QuSeC), the framework dynamically assigns security levels based on node capabilities. By transitioning between pure QKD, hybrid, and PQC modes, it ensures end-to-end quantum-safe protection regardless of the underlying node capabilities. The framework has been implemented and validated on a Kubernetes-based containerized testbed, demonstrating robust operation and performance across all scenarios. Results highlight its potential to support the gradual integration of quantum-safe technologies into existing infrastructures, paving the way toward fully quantum-safe communication networks.
With quantum computing nearing cryptographically relevant capabilities, classical file transfer systems face significant vulnerabilities, necessitating quantum-resistant solutions. This paper presents a hybrid architecture for secure file transfer, integrating a simulated BB84 quantum key distribution (QKD) protocol with adaptive encryption to achieve post-quantum security. The system intelligently selects one-time pad (OTP) cryptography for files up to 1MB, ensuring perfect secrecy, and AES-256-GCM for larger files, balancing efficiency and integrity, both using quantum-derived keys. Implemented in a TCP-based client-server framework, it employs a quantum key management module to maintain a pool of secure keys, with real-time error detection for eavesdropping. Experimental evaluation demonstrates robust key generation (error rate < 1% without eavesdropping, ~ 15% with interception), reliable encryption, and efficient transfers on standard hardware, eliminating the need for specialized quantum devices. This scalable, software-based solution advances quantum-enhanced protection for distributed file-sharing environments, addressing the urgent demand for practical post-quantum security.
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.
Email has long been a vital tool for personal and professional communication, but its security relies on traditional cryptographic algorithms that are expected to become vulnerable due to developments in quantum computing. The paper presents a secure application-layer email model compatible with existing frameworks, enhancing confidentiality using quantum-resistant methods. The system supports OAuth 2.0 and OpenID Connect, eliminating password-based authentication and improving access security while enabling integration with services like Gmail and Outlook. It uses symmetric encryption and a hybrid one-time pad–based key mechanism to simulate post-quantum secure keys. All encryption and decryption occur at the application layer, ensuring end-to-end security without modifying SMTP or IMAP, while maintaining compatibility with existing email systems.
As quantum computing continues to evolve and threaten traditional encryption methods, the need for secure email communication has never been higher. In this paper an unbreakable encryption framework: Quantum-Secured Mail System (QSMS), based on Quantum Key Distribution (QKD) using the No-Cloning Theorem is proposed. In contrast to traditional cryptography methods that are based on computational hardness, QKD provides secure key distribution using quantum mechanics, thus causing any eavesdropper action to be detectable in real time due to disturbance in the quantum system. Due to the No-Cloning Theorem, our solution limits the unauthorized replication of encryption keys, hence giving a fundamental improvement over security based on RSA. We propose QSMS, which is based on a hybrid cryptographic paradigm in which the QKD provides the security of the exchanged key and AES provides fast and efficient email encryption. The approach offers quantum-resilient security while maintaining compatibility with existing email systems, which is necessary for making the systems practically usable. “Real-time eavesdropping detection is also offered, with dynamic response to interception attempts regenerating encryption keys.” The QA-ree runs the performance analysis of the system to show that it can ensure a minimal Quantum Bit Error Rate(QBER) of only 1.52% which ensures the reliability of the key distribution with minimal error correction. The decryption and encryption times are still computationally efficient, thus allowing QKD-powered email security suitable for real-time transmission. By combining quantum cryptography with classical encryption, this approach enables a scalable and future-proof shield against both classical and quantum cyber threats.