The Signal protocol provides end-to-end security even when service providers are only partially trusted; however, it still lacks deniable authentication and does not resist quantum attacks in the messaging phase. This paper therefore presents a post-quantum enhancement of Signal that is efficient in both communication cost and end-to-end message latency. In the key-agreement phase, a lattice-based Gandalf ring signature is combined with the Kyber-1024 KEM to construct a pre-key mechanism that provides both post-quantum security and deniable authentication. In the messaging phase, a pair of post-quantum ratchets is layered on top of the classical Double Ratchet to form a classical-post-quantum hybrid ratchet, while the Skye key-derivation function and erasure-code-based block encapsulation reduce communication overhead. Experimental and analytical results show that the scheme preserves Signal’s end-to- end, forward, and post-compromise security, achieves practical post-quantum security and deniable authentication, and keeps the additional cryptographic delay negligible compared with typical network latency.
The Signal protocol provides end-to-end security even when service providers are only partially trusted; however, it still lacks deniable authentication and does not resist quantum attacks in the messaging phase. This paper therefore presents a post-quantum enhancement of Signal that is efficient in both communication cost and end-to-end message latency. In the key-agreement phase, a lattice-based Gandalf ring signature is combined with the Kyber-1024 KEM to construct a pre-key mechanism that provides both post-quantum security and deniable authentication. In the messaging phase, a pair of post-quantum ratchets is layered on top of the classical Double Ratchet to form a classical-post-quantum hybrid ratchet, while the Skye key-derivation function and erasure-code-based block encapsulation reduce communication overhead. Experimental and analytical results show that the scheme preserves Signal’s end-to- end, forward, and post-compromise security, achieves practical post-quantum security and deniable authentication, and keeps the additional cryptographic delay negligible compared with typical network latency.
In emerging environments such as cloud computing and the Internet of Things (IoT), secure authentication and key negotiation play a crucial role in protecting data transmitted over public networks. However, many existing authentication protocols are still designed based on classical public-key cryptography primitives, and quantum computing may threaten their security. To address this challenge, we propose a post-quantum authentication and key agreement protocol that uses the lattice-based Kyber key encapsulation mechanism (KEM). Our proposed protocol integrates cryptographic authentication, smart card protection, and post-quantum key encapsulation mechanisms, enabling mutual authentication between users and servers and securely establishing session keys. The security of the protocol is formally analyzed in the Real-or-Random (ROR) model under the random oracle assumption and the IND-CCA security of the underlying KEM scheme. Furthermore, through informal security analysis, we have further demonstrated that the protocol possesses important security properties, including anonymity, untraceability, perfect forward confidentiality, and resistance to known attacks. In addition, the computational cost and communication overhead of the proposed scheme are evaluated and compared with several representative authentication protocols. The results show that the proposed protocol can provide strong security while maintaining low computational cost and communication overhead.
Quantum computing poses a serious long-term risk to modern cryptographic systems, including the widely used Signal messaging protocol. This research work addresses that risk by integrating ML-KEM-768, a NIST-standardized post-quantum algorithm specified in FIPS 203, as an additional security layer within Signal Desktop. The proposed implementation applies a quantum-resistant wrapping layer to message content before encryption by Signal’s existing Double Ratchet protocol, thereby creating a hybrid cryptographic design that strengthens protection against both classical and quantum adversaries. The system uses ML-KEM-768 key encapsulation from the @noble/post-quantum library together with AES-256-GCM authenticated encryption from @noble/ciphers. This process produces 1088-byte KEM ciphertexts with 32-byte shared secrets and adds about 1104 bytes of overhead per message. Performance evaluation using two live Signal Desktop instances shows that the additional post-quantum layer introduces only modest latency. ML-KEM-768 encapsulation averages 0.67 ms, decapsulation averages 2.27 ms, and total message preparation overhead averages 13.0ms, which remains well below the 100 ms threshold commonly associated with instantaneous user interaction. Additionally, a second set of experiments evaluated image attachment encryption (100 KB, 500 KB, and 2 MB), confirming that ML-KEM-768 encapsulation cost remains constant at approximately 0.4 ms regardless of payload size while AES-256-GCM bulk encryption scales linearly, making the post-quantum overhead negligible for large media. A third stress test evaluated robustness under load, achieving 913 messages per second in burst mode with sub-millisecond wrap latency, and confirming stable performance with no degradation across sustained operation at 10 messages per second over 60 s. Overall, this work demonstrates that post-quantum cryptography can be integrated into a real messaging system in a practical manner, helping address the harvest now, decrypt later threat while preserving usability and strengthening long-term communication security.
The emergence of quantum computing poses a fundamental threat to current public key cryptographic systems. This threat is necessitating a transition to quantum resistant cryptographic alternatives in all the applications. In this work, we present the implementation of a practical hybrid end-to-end encryption system that combines classical and post-quantum cryptographic primitives to achieve both security and efficiency. Our system employs CRYSTALS-Kyber, a NIST-standardized lattice-based key encapsulation mechanism, for quantum-safe key exchange, coupled with AES-256-GCM for efficient authenticated symmetric encryption and SHA-256 for deterministic key derivation. The architecture follows a zero-trust model where a relay server facilitates communication without accessing plaintext messages or cryptographic keys. All encryption and decryption operations occur exclusively at client endpoints. The system demonstrates that NIST standardized post-quantum cryptography can be effectively integrated into practical messaging systems with acceptable performance characteristics, offering protection against both classical and quantum adversaries. As our focus is on implementation rather than on novelty, we also provide an open-source implementation to facilitate reproducibility and further research in post quantum secure communication systems.
Quantum computing is a potentially significant threat to classical cryptographic methods, commonly influenced for mobile communication security. In this paper, we propose one secure channel for private, personal mobile devices that are based not only on post-quantum cryptographically algorithm but also to secure communications in the quantum era. NIST-spec kemsKyber2 and Saber represent for irreplaceable session keys in communication against prospective quantum threats. The keys are periodically replaced in order to provide forward secrecy and to protect against an eventual compromise. In addition to the features of mobile platforms, the scheme employs a lightweight authentication protocol applied to lattice-based cryptography which has been shown to be secure and low resource overhead. Testing the proposed solution was practicable and wielded manageable results since it was performed on Android devices with an average key exchange latency of less than 250 milliseconds and a secure message delivery of below 500 milliseconds without compromising the AES-256 equivalence level of privacy. The engineers and software developers with the results from this study could safely claim that practically, it is indeed doable to transfer secure messages on mobile platforms in the post-quantum era and they’d have that same level of confidence with respect to the adoption of cipher suites based on post-quantum standards within any future communication systems.Keywords: Post-quantum cryptography, quantum-resistant encryption, key encapsulation mechanism (KEM), end-to-end encryption (E2EE), quantum key distribution (QKD), mobile communication security, lattice-based cryptography, publickey infrastructure (PKI), quantum computing threats.
Modern instant messaging systems require end-to-end (E2E) security guarantees while operating over server-mediated infrastructures that cannot be fully trusted. At the same time, the impending transition to post-quantum cryptography raises nontrivial challenges for the design of secure messaging protocols that preserve these guarantees. In this work, we present the design of a post-quantum end-to-end secure protocol for instant messaging applications under an untrusted relay model. The proposed construction relies on lattice-based primitives standardized by NIST, namely ML-KEM for key establishment and ML-DSA for authentication, and follows a Double-KEM pattern combined with explicit context binding to derive an E2E session key known only to the communicating clients. The server acts solely as an authenticated relay and never gains access to plaintext messages or session keys. In addition to the protocol design, we complement the protocol description with an automated symbolic verification using ProVerif, establishing injective mutual authentication and session-key secrecy under a Dolev–Yao adversary model. Finally, we characterize the computational cost of different authentication and verification policies and evaluate the performance of the handshake on heterogeneous cloud-based architectures. The results provide practical insight into the feasibility of deploying post-quantum end-to-end secure protocols within existing instant messaging infrastructures.
Most post-quantum (PQ) authentication and key agreement (AKA) protocols proposed for IoT, edge, and 6G systems still rely on ad-hoc lattice constructions, often derived from the Ring-Learning-With-Errors (RLWE) problem. Although mathematically elegant, these protocols repeatedly exhibit structural weaknesses, such as signal-leakage, key-reuse, and no mapping to NIST PQ security levels, that prevent real deployment. This article reviews these systemic issues and contrasts them with standardized, KEM-based PQ designs such as ML-KEM (Kyber). We show that encapsulation-based AKA architectures inherit both efficiency and full cryptographic assurance, eliminating the leakage channels and cumulative vulnerabilities inherent in RLWE protocols. We advocate a transition from ad-hoc lattice protocols to standardized encapsulation-based frameworks as the foundation for secure PQ authentication in consumer, IoT, and 6G systems.