A secure communication over an insecure channel without any prior exchanged key can be established with the help of an authentication step to exchange a public key and then using public-key cryptography such as RSA. In this work, we concentrate on message authentication protocols which require an extra authenticated channel. We also recall biometrics-based systems which are hard to implement and distance bounding-based authentication systems which are limited to closer communications. We sketch three generic attacks against any message authentication protocol, conclude on their maximal security, and study the security of some protocols. Finally, we propose a new protocol which achieves the same security level as that of SSH and GPG, but using much less authenticated bits.
A secure communication over an insecure channel without any prior exchanged key can be established with the help of an authentication step to exchange a public key and then using public-key cryptography such as RSA. In this work, we concentrate on message authentication protocols which require an extra authenticated channel. We also recall biometrics-based systems which are hard to implement and distance bounding-based authentication systems which are limited to closer communications. We sketch three generic attacks against any message authentication protocol, conclude on their maximal security, and study the security of some protocols. Finally, we propose a new protocol which achieves the same security level as that of SSH and GPG, but using much less authenticated bits.
Abstract. Manual authentication is a recently proposed model of communication motivated by the settings where the only trusted infrastructure is a low bandwidth authenticated channel, possibly realized by the aid of a human, that connects the sender and the receiver who are otherwise connected through an insecure channel and do not have any shared key or public key infrastructure. A good example of such scenarios is pairing of devices in Bluetooth. Manual authentication systems are studied in computational and information theoretic security model and protocols with provable security have been proposed. In this paper we extend the results in information theoretic model in two directions. Firstly, we extend a single receiver scenario to multireceiver case where the sender wants to authenticate the same message to a group of receivers. We show new attacks (compared to single receiver case) that can launched in this model and demonstrate that the single receiver lower bound 2 log(1/ɛ)+O(1) on the bandwidth of manual channel stays valid in the multireceiver scenario. We further propose a protocol that achieves this bound and provides security, in the sense that we define, if up to c receivers are corrupted. The second direction is the study of non-interactive protocols in unconditionally secure model. We prove that unlike computational security framework, without interaction a secure authentication protocol requires the bandwidth of the manual channel to be at least the same as the message size, hence non-trivial protocols do not exist. Key words: manual channel, (interactive) multireceiver authentication, security. 1
Biometric authentication has become integral to digital identity systems, particularly in smart cities where it enables secure access to services across governance, transportation, and public infrastructure. Centralised architectures, though widely used, pose privacy and scalability challenges due to the aggregation of sensitive biometric data. Decentralised identity frameworks offer better data sovereignty and eliminate single points of failure but introduce new security concerns, particularly around mutual trust among distributed devices. In such environments, biometric sensors and verification agents must authenticate one another before sharing sensitive biometric data. Existing authentication schemes rely on classical public key infrastructure, which is increasingly susceptible to quantum attacks. This work addresses this gap by proposing a quantum-secure communication protocol for decentralised biometric systems, built upon an enhanced Quantum Key Distribution (QKD) system. The protocol incorporates quantum-resilient authentication at both the classical and quantum layers of QKD: post-quantum cryptography (PQC) is used to secure the classical channel, while authentication qubits verify the integrity of the quantum channel. Once trust is established, QKD generates symmetric keys for encrypting biometric data in transit. Qiskit-based simulations show a key generation rate of 15 bits/sec and 89% efficiency. This layered, quantum-resilient approach offers scalable, robust authentication for next-generation smart city infrastructures.
Biometric authentication has become integral to digital identity systems, particularly in smart cities where it en-ables secure access to services across governance, trans-portation, and public infrastructure. Centralised archi-tectures, though widely used, pose privacy and scalabil-ity challenges due to the aggregation of sensitive biomet-ric data. Decentralised identity frameworks offer better data sovereignty and eliminate single points of failure but introduce new security concerns, particularly around mu-tual trust among distributed devices. In such environments, biometric sensors and verification agents must authenticate one another before sharing sensitive biometric data. Ex-isting authentication schemes rely on classical public key infrastructure, which is increasingly susceptible to quan-tum attacks. This work addresses this gap by propos-ing a quantum-secure communication protocol for decen-tralised biometric systems, built upon an enhanced Quan-tum Key Distribution (QKD) system. The protocol incorpo-rates quantum-resilient authentication at both the classical and quantum layers of QKD: post-quantum cryptography (PQC) is used to secure the classical channel, while authen-tication qubits verify the integrity of the quantum channel. Once trust is established, QKD generates symmetric keys for encrypting biometric data in transit. Qiskit-based sim-ulations show a key generation rate of 15 bits/sec and 89% efficiency. This layered, quantum-resilient approach offers scalable, robust authentication for next-generation smart city infrastructures.
Widely used communication and messaging protocols, e.g., TLS 1.3 and Signal, are insecure against an adversary with a quantum computer. We expect that post-quantum security will become mandatory for a new generation of cryptographic protocols in the nearest 10-15 years. The analysis of existing post-quantum secure cryptographic tools for key exchange, encryption and message authentication based on hard problems in codes, lattices, ring learning with errors and elliptic curve isogenies revealed their advantages and drawbacks. In particular, we conclude, that the main threat to communication and messaging protocols is only pre-quantum security of currently used Diffie-Hellman key exchange protocols. We summarize efficiency and safety results for each class of post-quantum cryptographic schemes and present an experimental implementation of isogeny-based Diffie-Hellman-like key exchange protocol as an illustration of their applicability.
Advances in the development of quantum technologies force to create new methods of secure information transfer over insecure networks and channels. In this article, we analyze some important properties of secure group messaging resilient to quantum computer attacks: message authentication and asynchronous key update. We consider options for ensuring message authentication and detect the difference between the requirements for this property in group communications and point-to-point channels. We define the structure of key information and preshared key packages for the new protocol based on the classic X3DH protocol.
Authentication is a well-studied area of classical cryptography: a sender A and a receiver B sharing a classical secret key want to exchange a classical message with the guarantee that the message has not been modified or replaced by a dishonest party with control of the communication line. In this paper we study the authentication of messages composed of quantum states. We give a formal definition of authentication in the quantum setting. Assuming A and B have access to an insecure quantum channel and share a secret, classical random key, we provide a non-interactive scheme that enables A to both encrypt and authenticate an m qubit message by encoding it into m+s qubits, where the error probability decreases exponentially in the security parameter s. The scheme requires a secret key of size 2m+O(s). To achieve this, we give a highly efficient protocol for testing the purity of shared EPR pairs. It has long been known that learning information about a general quantum state will necessarily disturb it. We refine this result to show that such a disturbance can be done with few side effects, allowing it to circumvent cryptographic protections. Consequently, any scheme to authenticate quantum messages must also encrypt them. In contrast, no such constraint exists classically. This reasoning has two important consequences: It allows us to give a lower bound of 2m key bits for authenticating m qubits, which makes our protocol asymptotically optimal. Moreover, we use it to show that digitally signing quantum states is impossible.