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Quantum Secure Anonymous Communication Networks

Mohammad Saidur Rahman, Stephen DiAdamo, Miralem Mehic, Charles Fleming

TL;DR

The paper addresses the quantum threat to anonymous communication by proposing a Tor-inspired network that uses quantum key distribution (QKD) and a passive quantum relay to distribute symmetric keys with information-theoretic security, removing the need for trusted nodes. It details system requirements, network design, and a three-stage key exchange protocol that maintains Tor's anonymity properties while safeguarding against quantum attacks. Security analysis emphasizes that the quantum relay remains untrusted and that classical post-processing ensures key integrity, with sequential circuit establishment preserving client-only knowledge of the full path. Practical challenges include distance and rate limitations of current QKD, scalability to multiple users, and engineering considerations for metropolitan-scale deployment; the work lays a foundation for quantum-secure anonymous networks and highlights directions for scaling this approach.

Abstract

Anonymous communication networks (ACNs) enable Internet browsing in a way that prevents the accessed content from being traced back to the user. This allows a high level of privacy, protecting individuals from being tracked by advertisers or governments, for example. The Tor network, a prominent example of such a network, uses a layered encryption scheme to encapsulate data packets, using 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 the 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.

Quantum Secure Anonymous Communication Networks

TL;DR

The paper addresses the quantum threat to anonymous communication by proposing a Tor-inspired network that uses quantum key distribution (QKD) and a passive quantum relay to distribute symmetric keys with information-theoretic security, removing the need for trusted nodes. It details system requirements, network design, and a three-stage key exchange protocol that maintains Tor's anonymity properties while safeguarding against quantum attacks. Security analysis emphasizes that the quantum relay remains untrusted and that classical post-processing ensures key integrity, with sequential circuit establishment preserving client-only knowledge of the full path. Practical challenges include distance and rate limitations of current QKD, scalability to multiple users, and engineering considerations for metropolitan-scale deployment; the work lays a foundation for quantum-secure anonymous networks and highlights directions for scaling this approach.

Abstract

Anonymous communication networks (ACNs) enable Internet browsing in a way that prevents the accessed content from being traced back to the user. This allows a high level of privacy, protecting individuals from being tracked by advertisers or governments, for example. The Tor network, a prominent example of such a network, uses a layered encryption scheme to encapsulate data packets, using 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 the 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.
Paper Structure (9 sections, 4 figures)

This paper contains 9 sections, 4 figures.

Table of Contents

  1. Introduction
  2. Quantum Threats Against the Tor Network and the Realizability
  3. A Quantum-Resistant Tor Network
  4. System Requirements
  5. Network Design
  6. Key Exchange Protocol
  7. Security and Privacy
  8. Practical Implementation Challenges
  9. Conclusion

Figures (4)

  • Figure 1: Three-layer encrypted message in a Tor network.
  • Figure 2: A predicted quantum threat level with time.
  • Figure 3: QKD enabled and Quantum Secure Tor design. The Tor Client is classically connected (blue) to the Entry, Middle, and Exit node via a Tor circuit. The Tor Client connects to the input of the quantum relay with a quantum channel (red) and the output, depending on the frequency, is sent to the particular Tor node.
  • Figure 4: Quantum secure key exchange in QKD enabled Tor network. The blue and red arrows represent classical and quantum communication respectively. The communicating parties are the Tor Client, the Quantum Relay, and the three Tor nodes. The classical messages are a Syn message (a synchronization request), Ack (an acknowledgment to the Syn) containing information of the QKD hardware for the Client, and Post are the post-processing messages for QKD. The quantum transmissions generate key material $\hat{K}_1, \hat{K}_2$, and $\hat{K}_3$.