Anonymous communication networks (ACNs) enable Internet browsing in a way that prevents accessed content from being traced back to the user. This provides a high level of privacy, protecting individuals from being tracked by advertisers, governments, and other entities. The Tor network, a prominent example of such a network, uses a layered encryption scheme to encapsulate data packets, employing Tor nodes to obscure the routing process before the packets enter the public Internet. While Tor is capable of providing substantial privacy, its encryption relies on schemes such as RSA and Diffie-Hellman for distributing symmetric keys, which are vulnerable to quantum computing attacks and are currently in the process of being phased out. To overcome this threat, we propose a quantum resistant alternative to RSA and Diffie-Hellman for distributing symmetric keys, namely, quantum key distribution (QKD). Standard QKD networks depend on trusted nodes to relay keys across long distances. However, reliance on trusted nodes in the quantum network does not meet the criteria necessary for establishing a Tor circuit in the ACN. We address this issue by developing a protocol and network architecture that integrates QKD without the need for trusted nodes, thus meeting the requirements of the Tor network and creating a quantum secure anonymous communication network.
Anonymous communication networks (ACNs) enable Internet browsing in a way that prevents accessed content from being traced back to the user. This provides a high level of privacy, protecting individuals from being tracked by advertisers, governments, and other entities. The Tor network, a prominent example of such a network, uses a layered encryption scheme to encapsulate data packets, employing Tor nodes to obscure the routing process before the packets enter the public Internet. While Tor is capable of providing substantial privacy, its encryption relies on schemes such as RSA and Diffie-Hellman for distributing symmetric keys, which are vulnerable to quantum computing attacks and are currently in the process of being phased out. To overcome this threat, we propose a quantum resistant alternative to RSA and Diffie-Hellman for distributing symmetric keys, namely, quantum key distribution (QKD). Standard QKD networks depend on trusted nodes to relay keys across long distances. However, reliance on trusted nodes in the quantum network does not meet the criteria necessary for establishing a Tor circuit in the ACN. We address this issue by developing a protocol and network architecture that integrates QKD without the need for trusted nodes, thus meeting the requirements of the Tor network and creating a quantum secure anonymous communication network.
Abstract To ensure the long-term security of anonymous communication against quantum computing threats, this paper proposes a QKD-assisted quantum secure onion routing protocol. The scheme employs a hybrid architecture comprising a star-topology QKD network, a classical onion routing network, and a blockchain-based pseudonym mechanism. By splitting trust between the central cloud and blockchain, the system prevents any single entity from compromising the complete path or session keys, thus balancing anonymity with scalability. Specifically, a quantum secure key agreement sub-protocol is designed: communicating parties XOR locally generated nonces with quantum keys and employ a hash family to achieve trust splitting. This method prevents both the central cloud and the blockchain from recovering session keys. Furthermore, a complete onion packet encapsulation process is established for layered encryption. Comprehensive analyses of correctness, security, and performance under practical QKD key rate constraints are provided. The results indicate that, under semi-honest and non-colluding assumptions, the proposed protocol achieves quantum secure anonymous communication while maintaining practical scalability.
The advance of quantum computing poses a significant threat to classical cryptography, compromising the security of current encryption schemes such as RSA and ECC. In response to this challenge, two main approaches have emerged: quantum cryptography and post-quantum cryptography (PQC). However, both have implementation and security limitations. In this paper, we propose a secure key distribution protocol for Quantum Key Distribution Networks (QKDN), which incorporates encapsulation techniques in the key-relay model for QKDN inspired by onion routing and combined with PQC to guarantee confidentiality, integrity, authenticity and anonymity in communication. The proposed protocol optimizes security by using post-quantum public key encryption to protect the shared secrets from intermediate nodes in the QKDN, thereby reducing the risk of attacks by malicious intermediaries. Finally, relevant use cases are presented, such as critical infrastructure networks, interconnection of data centers and digital money, demonstrating the applicability of the proposal in critical highsecurity environments.
The advancement of quantum computing threatens classical cryptographic methods, necessitating the development of secure quantum key distribution (QKD) solutions for QKD Networks (QKDN). In this paper, a novel key distribution protocol, Onion Routing Relay (ORR), that integrates onion routing (OR) with post-quantum cryptography (PQC) in a key-relay (KR) model is evaluated for QKDNs. This approach increases the security by enhancing confidentiality, integrity, authenticity (CIA principles), and anonymity in quantum-secure communications. By employing PQC-based encapsulation, ORR aims to avoid the security risks posed by intermediate malicious nodes and ensures end-to-end security. Our results show a competitive performance of the basic ORR model, against current KR and trusted-node (TN) approaches, demonstrating its feasibility and applicability in high-security environments maintaining a consistent Quality of Service (QoS). The results also show that while basic ORR incurs higher encryption overhead, it provides substantial security improvements without significantly impacting the overall key distribution time. Nevertheless, the introduction of an end-to-end authentication extension (ORR-Ext) has a significant impact on the Quality of Service (QoS), thereby limiting its suitability to applications with stringent security requirements.
The growing dependence on digital communications underscores the need to protect data as it travels through the network. Internet Protocol Security (IPsec) plays a central role, providing a robust framework to ensure the confidentiality, integrity, and authenticity of transmitted data. However, advances in Quantum Computing pose a significant threat to current public-key cryptographic schemes by enabling efficient solutions to factoring and discrete logarithm problems. A promising solution also arises from the quantum domain. Quantum Key Distribution (QKD) provides a security layer immune to any computational attacks, whether quantum or classical. While the rapid adoption of quantum-safe technologies is highly desirable, it is equally important to ensure the resilience of existing trusted infrastructures, as the introduction of novel technologies may also entail unforeseen challenges. Enabling an evolutionary path that brings our current security infrastructure to a quantum-safe one, protected against both present and future threats, is thus very important. This work proposes a solution that integrates emerging quantum technologies into the existing security and communications infrastructure to ensure long-term protection. We focus on IPsec —one of the most widely deployed security protocols— and combine it with Software-Defined Networking (SDN) and QKD to construct a novel network security infrastructure that is resilient against both classical and quantum computational threats. Building upon recent standardization initiatives and operational tools for QKD integration, we demonstrate advanced capabilities -including rekeying and secure key transport- on a field deployed QKD network operating within a shared quantum-classical production infrastructure.
The onion routing (OR) network Tor provides anonymity to its users by routing their encrypted traf-fic through three proxies (or nodes). The key cryptographic challenge, here, is to establish symmetric session keys using a secure key exchange between the anonymous users and the selected nodes. The Tor network currently employs a one-way authenticated key exchange (1W-AKE) protocol ntor for this purpose. Nevertheless, ntor as well as other known 1W-AKE protocols rely solely on some classical Diffie-Hellman (DH) type assumptions for their (forward) security, and thus privacy of today’s anony-mous communication cannot be ensured once quantum computers arrive. In this paper, we demonstrate utility of quantum-secure lattice-based cryptography towards solving this problem for onion routing. In particular, we present a novel hybrid 1W-AKE protocol (HybridOR) that is secure under the lattice-based ring learning with error (ring-LWE) assumption as well as the gap DH assumption. Due to its hybrid design, HybridOR is not only resilient against quantum attacks but also allows the OR nodes to use the current DH public keys and subsequently requires no modification to the current Tor public key infrastructure. Moreover, thanks to the recent progress in lattice-based cryp-tography in the form of efficient ring-based constructions, our protocol is also computationally more efficient than the currently employed 1W-AKE protocol ntor, and it only introduces small and manage-able communication overhead to the Tor protocol.
Abstract Anonymity in networked communication is vital for many privacy-preserving tasks. Secure key distribution alone is insufficient for high-security communications. Often, knowing who transmits a message to whom and when must also be kept hidden from an adversary. Here, we experimentally demonstrate five information-theoretically secure anonymity protocols on an eight user city-wide quantum network using polarisation entangled photon pairs. At the heart of these protocols is anonymous broadcasting, which is a cryptographic primitive that allows one user to reveal one bit of information while keeping their identity anonymous. For a network of n users, the protocols retain anonymity for the sender, given that no more than n − 2 users are colluding. This is an implementation of genuine multi-user cryptographic protocols beyond standard QKD. Our anonymous protocols enhance the functionality of any fully-connected Quantum Key Distribution network without trusted nodes.