Anonymous Communication Protocol Research Articles

RPM: Robust Anonymity at Scale

This work presents RPM, a scalable anonymous communication protocol suite using secure multiparty computation (MPC) with the offline-online model. We generate random, unknown permutation matrices in a secret-shared fashion and achieve improved (online) performance and the lightest communication and computation overhead for the clients compared to the state of art robust anonymous communication protocols. Using square-lattice shuffling, we make our protocol scale well as the number of clients increases. We provide three protocol variants, each targeting different input volumes and MPC frameworks/libraries. Besides, due to the modular design, our protocols can be easily generalized to support more MPC functionalities and security properties as they get developed. We also illustrate how to generalize our protocols to support two-way anonymous communication and secure sorting. We have implemented our protocols using the MP-SPDZ library suit and the benchmark illustrates that our protocols achieve unprecedented online phase performance with practical offline phases.

Secure Anonymous Communication on Corrupted Machines With Reverse Firewalls

The Snowden revelations in 2013 showed that user machines running cryptographic protocols might be stealthily corrupted by attackers (e.g., manufacturers and supply-chain intermediaries) who could tamper cryptographic implementations to insert backdoors to undermine cryptographic tools. To formalize such attacks, in CRYPTO 2014, Bellare <i>et al.</i> proposed the notion of Algorithm-Substitution Attack (ASA) which has been extensively studied since then. In this work, we turn to investigate the security of anonymous communication (AC) protocol—a well-known tool to protect user privacy on the Internet—in the case when user machines are corrupted. Specifically, we give a formal treatment of ASAs on the universal mixnet-based AC ( <inline-formula><tex-math notation="LaTeX">$\mathsf{U\text{-}Mix\text{-}AC}$</tex-math></inline-formula> ) protocols. We show that ASAs on <inline-formula><tex-math notation="LaTeX">$\mathsf{U\text{-}Mix\text{-}AC}$</tex-math></inline-formula> protocols could be more dangerous than previously thought by presenting attacks that are extremely powerful. As countermeasure, we adopt cryptographic reverse firewall (CRF), originally proposed by Mironov and Stephens-Davidowitz in EUROCRYPT 2015, to restore the security of <inline-formula><tex-math notation="LaTeX">$\mathsf{U\text{-}Mix\text{-}AC}$</tex-math></inline-formula> protocols in the presence of ASAs. We also implement proposed AC protocol, ASAs and CRFs for experimental evaluations, and the results show that the execution time of subverted algorithms is almost the same as that of faithful ones and our designed CRFs are effective to guard the security of <inline-formula><tex-math notation="LaTeX">$\mathsf{U\text{-}Mix\text{-}AC}$</tex-math></inline-formula> protocol.

OrgAn: Organizational Anonymity with Low Latency

There is a growing demand for network-level anonymity for delegates at global organizations such as the UN and Red Cross. Numerous anonymous communication (AC) systems have been proposed over the last few decades to provide anonymity over the internet; however, they introduce high latency overhead, provide weaker anonymity guarantees, or are difficult to deploy at the organizational networks. Recently, the PriFi system introduced a client/relay/server model that suitably utilizes the organizational network topology and proposes a low-latency, strong-anonymity AC protocol. Using an efficient lattice-based (almost) keyhomomorphic pseudorandom function and Netwon’s power sums, we present a novel AC protocol OrgAn in this client/relay/server model that provides strong anonymity against a global adversary controlling the majority of the network. OrgAn’s cryptographic design allows it to overcome several major problems with any realistic PriFi instantiation: (a) unlike PriFi, OrgAn avoids frequent, interactive, slot-agreement protocol among the servers; (b) a PriFi relay has to receive frequent communication from the servers, which can not only become a latency bottleneck but also reveal the access pattern to the servers and increases the chance of server collusion/coercion, while OrgAn servers are absent from any real-time process. We demonstrate how to make this public-key cryptographic solution scale equally well as the symmetric-cryptographic PriFi with practical pre-computation and storage requirements. Through a prototype implementation, we show that OrgAn provides similar throughput and end-to-end latency guarantees as PriFi, while still discounting the setup challenges in PriFi.

A protocol for anonymous short communications in social networks and its application to proximity-based services

Several innovative applications could be advantageously placed within social networks, to be effective, attractive, and pervasive. Examples of application domains that could benefit from social networks are e-democracy, e-participation, online surveys, crowdsourcing, and proximity-based services. In all the above cases, users’ anonymity could represent a considerable added value or could be even necessary to develop the service. We observe that all the above domains are characterized by the fact that only a few asynchronous messages should be exchanged. Therefore, we do not need the full communication power of anonymous communication networks, in which low-latency and connection-oriented communication should be supported. On the other hand, unlike communication networks, the threat model we have to consider assumes the presence of an adversary (represented by an honest-but-curious social network provider) able to monitor the entire flow of the exchanged messages. In this paper, we propose an anonymous communication protocol for short communications in social networks, based on a collaborative approach. The proposed solution hides from the social network provider not only the content of the messages but also the communication itself, which, per se, can result in considerable privacy leakage (think of the case of proximity testing performed between two users). This enables the implementation, within the social network, of the above-mentioned applications. To give a concrete proof of this statement, we develop a privacy-preserving proximity-based solution which provides both symmetric and asymmetric proximity testing entirely within social networks.

A Framework for Formal Analysis of Anonymous Communication Protocols

Anonymity is the property of keeping secret the identity of the user performing a certain action. The need for anonymity may arise in a wide range of situations, like electronic voting, Web browsing, and so on. In order to verify the anonymity of security protocols, a framework for formal analysis of anonymous communication protocols is proposed. In this framework, we define operational semantics for security protocols using a labelled transition system; the transition relation is defined by the transition rules, which include create rule, send rule, and receive rule. In addition, the formal description of intruder model in this framework is given. The proposed intruder model specifies the capabilities of the intruder and is weaker than the Dolev–Yao model. Moreover, the concepts of mapping and trace equivalence are proposed; the sender anonymity is formally defined. To illustrate the applicability of proposed framework, we explore the use of probabilistic model checking tool PRISM to analyze the sender anonymity of Crowds protocol. The experimental results show the relationship between sender anonymity and the number of nodes, path reformulations, and forwarding probability, which provides a good way about how to protect the sender anonymity of anonymous communication protocols.

A biometric secured anonymous communication protocol for Vehicular Ad hoc Network

Communication security in Vehicular Ad hoc NETwork (VANET) is a significant concern. Existing schemes for secure communication in VANET suffer from high computation, communication complexities, and exploitable vulnerabilities. This paper proposes a multi-level biometric-based scheme for authentication and anonymous communication in VANET. The use of fingerprint hashing and modified Blom’s scheme provides a high level of security to our scheme. Furthermore, the proposed scheme achieves lower computational and communication costs than the existing schemes due to lightweight operations and minimal message exchange required to complete the authentication process. The security of the proposed scheme is verified using the Real or Random (RoR) model, ProVerif tool, and informal security analysis. The results of the ns-2 simulation show the practical applicability and network performance of our scheme compared to existing schemes.

Anonymous communication protocol over quantum networks

We propose a W state-based protocol for anonymously transmitting quantum messages in a quantum network. Different from the existing protocols [A. Unnikrishnan, et al., Phys. Rev. Lett. 122, 240501 (2019)], the proposed protocol can be effectively implemented in the network only equipped with quantum channels and regular broadcast channels. Throughout the design procedure, we develop three sub-protocols using the W state, including the quantum collision detection protocol and the quantum notification protocol. Moreover, together with the conventional anonymous entanglement protocol, the whole anonymous communication protocol has been constructed. Finally, we examine the correctness and security of the proposed quantum anonymous communication protocol.

Quantum communication for sender anonymity based on single-particle with collective detection

Nowadays, identity protection has turned into a fundamental demand for online activities. Currently, the present quantum anonymous communication protocols mostly rely on multi-entanglement. In this paper, we propose an anonymous communication protocol for anonymous sender by using single-particle states. The protocol can be extended to a communication protocol where the sender and receiver are fully anonymous with the message kept secret. In terms of security, our protocol is designed to comply with the technique of collective detection. Compared to the step-by-step detection, collective detection, in which the participants perform detection only once, reduces the complexity of the protocol to some extent. Moreover, we analytically demonstrate the security of the protocol in the face of active attacks. Any active attack employed by an external or internal attacker cannot reveal any useful information about the sender’s identity. Meanwhile, any malicious behavior will be detected by honest participants.

Towards practical anonymous quantum communication: A measurement-device-independent approach

The multipartite Greenberger-Horne-Zeilinger (GHZ) entangled state is an important resource for anonymous quantum communication tasks. But its low intensity and fragility limit the practical applications of these anonymous communication tasks under current conditions. Here, we present a feasible anonymous communication protocol in the measurement-device-independent framework. We analyze its performance in a quantum network under certain types of noise. Then we compare the performance of our protocol with the GHZ-state-based anonymous protocol. We demonstrate that our protocol has a unique advantage, i.e., it can tolerate an arbitrary number of nonresponsive nodes. We prove that the security of our protocol in an active adversary scenario in which active malicious agents and an untrusted ancillary node are taken into account. Utilizing the measurement-device-independent technology, our proposal suggests an important avenue for practical anonymous quantum communication.

PriFi: Low-Latency Anonymity for Organizational Networks

Abstract Organizational networks are vulnerable to trafficanalysis attacks that enable adversaries to infer sensitive information fromnetwork traffic—even if encryption is used. Typical anonymous communication networks are tailored to the Internet and are poorly suited for organizational networks.We present PriFi, an anonymous communication protocol for LANs, which protects users against eavesdroppers and provides high-performance traffic-analysis resistance. PriFi builds onDining Cryptographers networks (DC-nets), but reduces the high communication latency of prior designs via a new client/relay/server architecture, in which a client’s packets remain on their usual network path without additional hops, and in which a set of remote servers assist the anonymization process without adding latency. PriFi also solves the challenge of equivocation attacks, which are not addressed by related work, by encrypting traffic based on communication history. Our evaluation shows that PriFi introduces modest latency overhead (≈ 100ms for 100 clients) and is compatible with delay-sensitive applications such as Voice-over-IP.

Examining the correctness of anonymity for practical quantum networks

In a recent paper [A. Unnikrishnan et al., Phys. Rev. Lett. 122, 240501 (2019)], a quantum anonymous communication protocol was proposed in the presence of malicious agents and an untrusted source. Here, we point out that malicious agents can change the generated anonymous entanglement between the sender and the receiver without being detected, which means that the correctness of the generated anonymous entanglement should be reexamined. The way to check the above correctness is discussed.

Privacy-Aware Secure Anonymous Communication Protocol in CPSS Cloud Computing

Cloud computing has emerged as a promising paradigm for the Internet of Things (IoT) and Cyber-Physical-Social Systems (CPSS). However, the problem of how to ensure the security of data transmission and data storage in CPSS is a key issue to address. We need to protect the confidentiality and privacy of users’ data and users’ identity during the transmission and storage process in CPSS. In order to avoid users’ personal information leakage from IoT devices during the process of data processing and transmitting, we propose a certificateless encryption scheme, and conduct a security analysis under the assumption of Computational Diffie-Hellman(CDH) Problem. Furthermore, based on the proposed cryptography mechanism, we achieve a novel anonymous communication protocol to protect the identity privacy of communicating units in CPSS. In the new protocol, an anonymous communication link establishment method and an anonymous communication packet encapsulation format are proposed. The Diffie-Hellman key exchange algorithm is used to construct the anonymous keys distribution method in the new link establishment method. And in the new onion routing packet encapsulation format, the session data are firstly separated from the authentication data to decrease the number of cryptography operations. That is, by using the new onion routing packet we greatly reduces the encryption operations and promotes the forwarding efficiency of anonymous messages, implementing the privacy, security and efficiency in anonymous communication in cyber-physical-social systems.

Another Look at Anonymous Communication

Anonymous communication is desirable for personal, financial, and political reasons. Despite the abundance of frameworks and constructions, anonymity definitions are usually either not well defined or too complicated to use. In between are ad-hoc definitions for specific protocols which sometimes only provide weakened anonymity guarantees. This paper addresses this situation from the perspectives of syntax, security definition, and construction. We propose simple yet expressive syntax and security definition for anonymous communication. Our syntax covers protocols with different operational characteristics. We give a hierarchy of anonymity definitions, starting from the strongest possible to several relaxations. We also propose a modular construction from any key-private public-key encryption scheme, and a new primitive—oblivious forwarding protocols, of which we give two constructions. The first is a generic construction from any random walk over graphs, while the second is optimized for the probability of successful delivery, with experimental validation for our optimization. Anonymity is guaranteed even when the adversary can observe and control all traffic in the network and corrupt most nodes, in contrast to some efficient yet not-so-anonymous protocols. We hope this work suggests an easier way to design and analyze efficient anonymous communication protocols in the future.

Anonymity for Practical Quantum Networks.

Quantum communication networks have the potential to revolutionize information and communication technologies. Here we are interested in a fundamental property and formidable challenge for any communication network, that of guaranteeing the anonymity of a sender and a receiver when a message is transmitted through the network, even in the presence of malicious parties. We provide the first practical protocol for anonymous communication in realistic quantum networks.

A Survey on Routing in Anonymous Communication Protocols

The Internet has undergone dramatic changes in the past 2 decades and now forms a global communication platform that billions of users rely on for their daily activities. While this transformation has brought tremendous benefits to society, it has also created new threats to online privacy, such as omnipotent governmental surveillance. As a result, public interest in systems for anonymous communication has drastically increased. In this work, we survey previous research on designing, developing, and deploying systems for anonymous communication. Our taxonomy and comparative assessment provide important insights about the differences between the existing classes of anonymous communication protocols.

A Semistructured Random Identifier Protocol for Anonymous Communication in SDN Network

Traffic analysis is an effective mean for gathering intelligence from within a large enterprise’s local network. Adversaries are able to monitor all traffic traversing a switch by exploiting just one vulnerability in it and obtain valuable information (e.g., online hosts and ongoing sessions) for further attacking, while administrators have to patch all switches as soon as possible in hope of eliminating the vulnerability in time. Moving Target Defense (MTD) is a new paradigm for reobtaining the upper hand in network defense by dynamically changing attack surfaces of the network. In this paper, we propose U-TRI (unlinkability through random identifier) as a moving target technique for changing the information-leaking identifiers within PDUs for SDN network. U-TRI is based on VIRO protocol and implemented with the help of OpenFlow protocol. U-TRI employs an independent, binary tree-structured, periodically and randomly updating identifier to replace the first part of the static MAC address in PDU, and assigns unstructured random values to the remaining part of the MAC address. U-TRI also obfuscates identifiers in the network layer and transport layer in an unstructured manner. Such a semistructured random identifier enables U-TRI to significantly weaken the linkage between identifiers and end-hosts as well as communication sessions, thus providing anonymous communication in SDN network. The result of analysis and experiments indicates that U-TRI dramatically increases the difficulty of traffic analysis with acceptable burdens on network performance.

Anonymity Trilemma: Strong Anonymity, Low Bandwidth Overhead, Low Latency—Choose Two

This work investigates the fundamental constraints of anonymous communication (AC) protocols. We analyze the relationship between bandwidth overhead, latency overhead, and sender anonymity or recipient anonymity against the global passive (network-level) adversary. We confirm the trilemma that an AC protocol can only achieve two out of the following three properties: strong anonymity (i.e., anonymity up to a negligible chance), low bandwidth overhead, and low latency overhead. We further study anonymity against a stronger global passive adversary that can additionally passively compromise some of the AC protocol nodes. For a given number of compromised nodes, we derive necessary constraints between bandwidth and latency overhead whose violation make it impossible for an AC protocol to achieve strong anonymity. We analyze prominent AC protocols from the literature and depict to which extent those satisfy our necessary constraints. Our fundamental necessary constraints offer a guideline not only for improving existing AC systems but also for designing novel AC protocols with non-traditional bandwidth and latency overhead choices.

Establishing secure and anonymous communication channel: KEM/DEM-based construction and its implementation

Several cryptographic tools provide anonymity in a cryptographic sense, but solely using such a tool does not guarantee anonymity; for example, even if the underlying cryptographic primitives enable anonymity in some sense, a communication system using these tools may reveal the senders’ IP address. Moreover, since a certificate of public key infrastructure contains information of a key holder, and that contradicts anonymity of the key holder, the certificate must be removed. Therefore, it seems difficult to check the validity of the public key in an anonymous environment. That is, constructing a secure and anonymous communication protocol, where end-to-end encryption and anonymous authentication are achieved simultaneously, is an important issue to be solved.In ACM SAC 2014 (and IEEE Trans. Emerging Topics Comput. 2016), such a protocol was proposed, where it applies identity-based encryption (IBE) for packet encryption without contradicting anonymity. However, this protocol is inefficient and approximately 20 times slower than that of SSL communications because IBE requires heavy cryptographic pairing computations.In this paper, we propose a more efficient, secure, and anonymous communication protocol, which achieves the same security level as the IBE-based protocol does. The protocol is exempted from pairing computation for establishing a secure channel by applying hybrid encryption instead of IBE. We implement the protocol and show that it is more efficient (overall approximately 1.2 times faster) than the IBE-based protocol. In particular, the decryption algorithm of our protocol is several hundred times faster than that of the IBE-based protocol. In our protocol, we employ the ElGamal KEM scheme and 128-bit AES as the underlying KEM and DEM schemes, respectively, and we have used the TEPLA library for the prototype implementation.

AnoA: A Framework for Analyzing Anonymous Communication Protocols

Anonymous communication (AC) protocols such as the widely used Tor network have been designed to provide anonymity over the Internet to their participating users. While AC protocols have been the subject of several security and anonymity analyses in the last years, there still does not exist a framework for analyzing these complex systems and their different anonymity properties in a unified manner.&#x0D; &#x0D; In this work we present AnoA: a generic framework for defining, analyzing, and quantifying anonymity properties for AC protocols. In addition to quantifying the (additive) advantage of an adversary in an indistinguishability-based definition, AnoA uses a multiplicative factor, inspired from differential privacy. AnoA enables a unified quantitative analysis of well-established anonymity properties, such as sender anonymity, sender unlinkability, and relationship anonymity. AnoA modularly specifies adversarial capabilities by a simple wrapper-construction, called adversary classes. We examine the structure of these adversary classes and identify conditions under which it suffices to establish anonymity guarantees for single messages in order to derive guarantees for arbitrarily many messages. This then leads us to the definition of Plug’n’Play adversary classes (PAC), which are easy-to-use, expressive, and satisfy this condition. We prove that our framework is compatible with the universal composability (UC) framework and show how to apply AnoA to a simplified version of Tor against passive adversaries, leveraging a recent realization proof in the UC framework.

Source Anonymity in WSNs against Global Adversary Utilizing Low Transmission Rates with Delay Constraints.

Wireless sensor networks (WSN) are deployed for many applications such as tracking and monitoring of endangered species, military applications, etc. which require anonymity of the origin, known as Source Location Privacy (SLP). The aim in SLP is to prevent unauthorized observers from tracing the source of a real event by analyzing the traffic in the network. Previous approaches to SLP such as Fortified Anonymous Communication Protocol (FACP) employ transmission of real or fake packets in every time slot, which is inefficient. To overcome this shortcoming, we developed three different techniques presented in this paper. Dummy Uniform Distribution (DUD), Dummy Adaptive Distribution (DAD) and Controlled Dummy Adaptive Distribution (CAD) were developed to overcome the anonymity problem against a global adversary (which has the capability of analyzing and monitoring the entire network). Most of the current techniques try to prevent the adversary from perceiving the location and time of the real event whereas our proposed techniques confuse the adversary about the existence of the real event by introducing low rate fake messages, which subsequently lead to location and time privacy. Simulation results demonstrate that the proposed techniques provide reasonable delivery ratio, delay, and overhead of a real event's packets while keeping a high level of anonymity. Three different analysis models are conducted to verify the performance of our techniques. A visualization of the simulation data is performed to confirm anonymity. Further, neural network models are developed to ensure that the introduced techniques preserve SLP. Finally, a steganography model based on probability is implemented to prove the anonymity of the techniques.