Strong Anonymity Research Articles

Comprehensive Anonymity Trilemma: User Coordination is not enough

Abstract For anonymous communication networks (ACNs), Das et al. recently confirmed a long-suspected trilemma result that ACNs cannot achieve strong anonymity, low latency overhead and low bandwidth overhead at the same time. Our paper emanates from the careful observation that their analysis does not include a relevant class of ACNs with what we call user coordination where users proactively work together towards improving their anonymity. We show that such protocols can achieve better anonymity than predicted by the above trilemma result. As the main contribution, we present a stronger impossibility result that includes all ACNs we are aware of. Along with our formal analysis, we provide intuitive interpretations and lessons learned. Finally, we demonstrate qualitatively stricter requirements for the Anytrust assumption (all but one protocol party is compromised) prevalent across ACNs.

A Novel Multiserver Authentication Scheme Using Proxy Resignature With Scalability and Strong User Anonymity

As the indispensable part of the security demand in a distributed system, a variety of online services need to be protected from unauthorized access. Multiserver authentication (MA) is one of the most effective and promising approaches to guarantee one party the authenticity of its partner in the distributed system. In this article, we first elaborate the problem of scalability for MA protocol. After that, a two-level framework for multiserver environment is proposed to convert single-server authentication to MA with provable security and perfect scalability. Also, we give an instance of our novel infrastructure by adopting the idea of proxy resignature to achieve strong anonymity. Furthermore, the security analysis and performance evaluation show that our protocol is secure and practical.

An Efficient One-Way Authenticated Key Exchange Protocol for Anonymity Networks

Authenticated key exchange (AKE) is a crucial cryptographic primitive used for establishing an authenticated and confidential communication channel between parties, which has been widely used in our daily life when we surf on the Internet. However, in past decades mutual AKE protocols have been studied extensively in theory, while in many practical environments such as in the Tor anonymity network the mutual authentication property is undesirable. Meanwhile, considering privacy protection is getting more and more attention and one-way AKE protocols play an important role in privacy protection, so no matter in theory or in practice, it is quite meaningful to conduct research on the one-way AKE protocols. In this article, we present a new efficient anonymous one-way AKE protocol, which has strong anonymity and security properties guarantee, and efficiency advantages. Moreover, our new scheme has tight security reduction and is formally proved secure in the random oracle model under the Gap-DH and XCR signature security assumptions.

Mutual exclusion in fully anonymous shared memory systems

Process anonymity has been studied for a long time. Memory anonymity is more recent. In an anonymous memory system, there is no a priori agreement among the processes on the names of the shared registers. As an example, a shared register named A by a process p and a shared register named B by another process q may correspond to the very same register X, while the same name C may correspond to different register names for the processes p and q, and this remains unknown to the processes. This article introduces the full anonymous model, namely a model in which both the processes and the registers are anonymous. A fundamental question is then “is this model meaningful?”, which can be translated as “can non-trivial fundamental problems be solved in such a very weak computing model?”This article answers this question positively. More precisely, it presents a deadlock-free mutual exclusion algorithm in such a fully anonymous model where the anonymous registers are read/modify/write registers. This algorithm assumes that m (the number of shared registers) and n (the number of processes) are such that m is relatively prime with all the integers ℓ∈{1,...,n}. Combined with a previous result (PODC 2019) on mutual exclusion in memory anonymous (but not process anonymous) systems, it follows that this condition is both necessary and sufficient for the existence of such an algorithm in fully anonymous systems. As far as we know, this is the first time full anonymity is considered, and where a non-trivial concurrency-related problem is solved in such a very strong anonymity context.

Robust Conditional Privacy-Preserving Authentication based on Pseudonym Root with Cuckoo Filter in Vehicular Ad Hoc Networks

Numerous privacy-preserving authentication schemes have been proposed but vehicular ad hoc networks (VANETs) still suffer from security and privacy issues as well as computation and communication overheads. In this paper, we proposed a robust conditional privacy-preserving authentication scheme based on pseudonym root with cuckoo filter to meet security and privacy requirements and reduce computation and communication overheads. In our proposed scheme, we used a new idea to generate pseudonyms for vehicles where each on-board unit (OBU) saves one pseudonym, named as “pseudonym root,” and generates all pseudonyms from the same pseudonym. Therefore, OBU does not need to enlarge its storage. In addition, the scheme does not use bilinear pairing operation that causes computation overhead and has no certification revocation list that leads to computation and communication overheads. The proposed scheme has lightweight mutual authentication among all parties and just for once. Moreover, it provides strong anonymity to preserve privacy and resists ordinary attacks. We analyzed our proposed scheme and showed that it meets security and privacy requirements of VANETs and is more efficient than traditional schemes. The communication and computation overheads were also discussed to show the cost-effectiveness of the proposed scheme.

Authenticated Key Agreement Scheme with Strong Anonymity for Multi-Server Environment in TMIS.

The technology of Internet of Things (IoT) has appealed to both professionals and the general public to its convenience and flexibility. As a crucial application of IoT, telecare medicine information system (TMIS) provides people a high quality of life and advanced level of medical service. In TMIS, smart card-based authenticated key agreement schemes for multi-server architectures have gathered momentum and positive impetus due to the conventional bound of a single server. However, we demonstrate that most of the protocols in the literatures can not implement strong security features in TMIS, such as Lee et al.'s and Shu's scheme. They store the identity information directly, which fail to provide strong anonymity and suffer from password guessing attack. Then we propose an extended authenticated key agreement scheme (short for AKAS) with strong anonymity for multi-server environment in TMIS, by enhancing the security of the correlation parameters stored in the smart cards and calculating patients' dynamic identities. Furthermore, the proposed chaotic map-based scheme provides privacy protection and is formally proved under Burrows-Abadi-Needham (BAN) logic. At the same, the informal security analysis attests that the AKAS scheme not only could resist the multifarious security attacks but also improve efficiency by 21% compared with Lee et al.'s and Shu's scheme.

A Privacy-Aware Data Aggregation Scheme for Smart Grid Based on Elliptic Curve Cryptography With Provable Security Against Internal Attacks

In smart grids (SGs), smart meters (SMs) are usually deployed to collect and transmit customers' electricity consumption data in real-time to the control center. Due to the open nature of the SG communication, several privacy-preserving data aggregation schemes have been proposed to protect the privacy of customers. However, most of these schemes cannot protect against internal attackers and they are not efficient, since SMs are constrained in processing, memory, and computing capabilities. To address these problems, the authors propose a privacy-aware lightweight data aggregation scheme against internal attackers based on Elliptic Curve Cryptography (ECC). The scheme satisfies all the security requirements of SG, and supports conditional traceability, strong anonymity and autonomy. The authors demonstrate that the proposed scheme provides confidentiality based on the Computational Diffie-Hellman (CDH) assumption and unforgeability in the security model based on the intractability of the Discrete Logarithm (DL) problem. Extensive performance analysis shows that the proposed scheme is very efficient.

Password-based Selective Linkable Convertible Ring Blind Signature

Ring signature has become an important way of privacy protection because of its anonymity and the spontaneity of ring members. It has been widely used in the field of information security. Password-based alternative linkable convertible ring blind signature scheme combines the advantages of strong anonymity of ring signature and blindness of blind signature to signature message, and adds the optional linkable and convertible characteristics, which makes it more secure than other schemes, and can also transform ring signature into ordinary signature in special occasions. At the same time, under the random oracle model, the scheme satisfies the unforgeability under the adaptive selection message attack. Performance analysis shows that the scheme has high operating efficiency.

A pairing‐free identity‐based handover AKE protocol with anonymity in the heterogeneous wireless networks

SummaryNowadays, seamless roaming service in heterogeneous wireless networks attracts more and more attention. When a mobile user roams into a foreign domain, the process of secure handover authentication and key exchange (AKE) plays an important role to verify the authenticity and establish a secure communication between the user and the access point. Meanwhile, to prevent the user's current location and moving history information from being tracked, privacy preservation should be also considered. However, existing handover AKE schemes have more or less defects in security aspects or efficiency. In this paper, a secure pairing‐free identity‐based handover AKE protocol with privacy preservation is proposed. In our scheme, users' temporary identities will be used to conceal their real identities during the handover process, and the foreign server can verify the legitimacy of the user with the home server's assistance. Besides, to resist ephemeral private key leakage attack, the session key is generated from the static private keys and the ephemeral private keys together. Security analysis shows that our protocol is provably secure in extended Canetti‐Krawczyk (eCK) model under the computational Diffie‐Hellman (CDH) assumption and can capture desirable security properties including key‐compromise impersonation resistance, ephemeral secrets reveal resistance, strong anonymity, etc. Furthermore, the efficiency of our identity‐based protocol is improved by removing pairings, which not only simplifies the complex management of public key infrastructure (PKI) but also reduces the computation overhead of ID‐based cryptosystem with pairings. It is shown that our proposed handover AKE protocol provides better security assurance and higher computational efficiency for roaming authentication in heterogeneous wireless networks.

An Association Ring Signature for Block Chain E-Money Transactions

Block chain is widely used in the financial field for its characteristics of decentralization, anonymity and trust. Electronic money payment is an important application hotspot. Ring signature is widely used in strong anonymous authentication such as electronic cash and electronic voting because of its unconditional anonymity, spontaneity and flexible group structure. Among them, the correlation ring signature can prove whether two signatures are issued by the same person without revealing the identity of the real signer. Therefore, the signature right breach can be avoided based on the premise of guaranteeing anonymity, such as repeated voting, electronic money repetition cost and so on. Most of the existing correlation ring signature security is based on the discrete logarithm problem, and most of the schemes result in the degradation of anonymity because of strong association. These methods do not apply to the block chain electronic currency transaction scene with strong anonymity. Therefore, this paper first proposes a blockchain-based electronic currency transaction security model. The model ensures not only the anonymity of both parties but also a certain degree of traceability. In order to support these two characteristics, this paper proposes an association ring signature method based on large integer decomposition problem. This method has strong anonymity and can be applied to blockchain scenes. On the other hand, it can be converted into group signatures in specific scenarios. It is therefore traceable. Finally, the adaptive selection message of the scheme and the unforgeability under the selection of public key attack are proved under the random oracle model.

Anonymous roaming authentication protocol for wireless network with backward unlinkability, exculpability and efficient revocation check

Secure seamless roaming in a wireless network is desirable in today’s highly dynamic world. Providing revocation and non-traceability in an efficient two-party roaming authentication protocol is a challenging task. Conventional two-party protocols utilize pseudo-identities or group signature with revocation tokens to support non-traceability and strong user anonymity. Among the group signature based authentication schemes, only Priauth scheme has non-traceability or backward/forward unlinkability and the mobile user does not have to do any computation after each revocation. Despite all the advantages, Priauth scheme does not support exculpability or in other words the home server knows the group signing key of the mobile user. In case of dispute, the mobile user can deny that it generated signature because the mobile user and the home server both know the signing key of the mobile user. Thus, the mobile user cannot be held accountable. Moreover, Priauth has high revocation cost due to pairing operation performed for each revoked token in the revocation list during revocation checking at the foreign server. In addition, the existing group signature based authentication schemes are not provably secure in the random oracle model. We propose a provably secure two-party authentication protocol using group signature scheme which overcomes the weaknesses of Priauth scheme by supporting exculpability, backward unlinkability and using exponential operation instead of costlier pairing operation during revocation checking.

A Privacy-Preserving Passenger Information Management Scheme for Road Transport System in Nigeria

In Nigeria road transport system, the conventional paper-based manifest allows passengers' information to be collected and used for emergency purposes. However, the privacy of passengers is not preserved because an adversary can easily obtain these sensitive information for malicious intentions such as extortion, kidnapping, route monitoring, assassination, spying, and so forth. To address this problem, we develop a provably secure scalable lightweight data management scheme for achieving data privacy, authenticity, integrity, and confidentiality in road transport systems. An efficient authentication scheme is developed to achieve data authenticity and integrity, and a novel perturbation to guarantee data privacy and confidentiality. We show that the scheme is provably secure in the random oracle model based on Discrete Logarithm Assumption (DLA). In addition, the scheme achieves strong anonymity, conditional traceability and resistance to various attacks, and provides countermeasure against privilege escalation. The novel perturbation prevents gleaning by adversaries and ensures perfect reconstruction of original data from the perturbed data. Compared with related schemes, the performance evaluation and comparisons show an improved efficiency in terms of computation and communication overheads. Therefore, the proposed scheme is suitable for practical applications in the road transport system in Nigeria to overcome the weaknesses and limitations of the paper manifest.

Strong anonymous mobile payment against curious third-party provider

M-commerce provides convenient services and has developed rapidly in recent years. But security and privacy have always been major concerns for most users. Among existing payment systems, PayPal as well as Alipay has a third-party payment provider (TPP) but does not provide anonymity. Bitcoin provides anonymity but its decentralized framework without TPP causes high energy consumption and security attack issues. Further information can be deduced from the public decentralized ledger, Bitcoin cannot offer strong privacy guarantees. Therefore, unifying strong anonymity, security and efficiency is challenging in mobile payment. This paper proposes a strong anonymous mobile payment against a curious third-party provider (SATP). A ticket as a new means of payment is partially blindly signed by TPP using certificateless cryptographic primitives. SATP can ensure confidentiality of payment data, non-repudiation and revocation of payment operation, and anonymity of payer’s identity. Especially, it can enable a user to pay anonymously even in face of a curious TPP. Performance analysis shows that SATP avoids high energy consumption like Bitcoin, and its communication cost is less than that of the existing anonymous research work.

Anonymous broadcasting of classical information with a continuous-variable topological quantum code

Broadcasting information anonymously becomes more difficult as surveillance technology improves, but remarkably, quantum protocols exist that enable provably traceless broadcasting. The difficulty is making scalable entangled resource states that are robust to errors. We propose an anonymous broadcasting protocol that uses a continuous-variable surface-code state that can be produced using current technology. High squeezing enables large transmission bandwidth and strong anonymity, and the topological nature of the state enables local error mitigation.

A Provably Secure Anonymous Authenticated Key Exchange Protocol Based on ECC for Wireless Sensor Networks

In wireless sensor networks, users sometimes need to retrieve real‐time data directly from the sensor nodes. Many authentication protocols are proposed to address the security and privacy aspects of this scenario. However, these protocols still have security loopholes and fail to provide strong user anonymity. In order to overcome these shortcomings, we propose an anonymous authenticated key exchange protocol based on Elliptic Curves Cryptography (ECC). The novel protocol provides strong user anonymity such that even the gateway node and the sensor nodes do not know the real identity of the user. The security of the proposed protocol is conducted in a well‐defined security model under the CDH assumption. Compared with other related protocols, our protocol is efficient in terms of communication and enjoys stronger security. The only disadvantage is that our protocol consumes more computation resources due to the usage of asymmetric cryptography mechanisms to realize strong anonymity. Consequently, our protocol is suitable for applications which require strong anonymity and high security in wireless sensor networks.

A Privacy-Preserving Fog Computing Framework for Vehicular Crowdsensing Networks

Recently, the study of road surface condition monitoring has drawn great attention to improve the traffic efficiency and road safety. As a matter of fact, this activity plays a critical role in the management of the transportation infrastructure. Trustworthiness and individual privacy affect the practical deployment of the vehicular crowdsensing network. Mobile sensing as well as the contemporary applications are made use of problem solving. The fog computing paradigm is introduced to meet specific requirements, including the mobility support, low latency, and location awareness. The fog-based vehicular crowdsensing network is an emerging transportation management infrastructure. Moreover, the fog computing is effective to reduce the latency and improve the quality of service. Most of the existing authentication protocols cannot help the drivers to judge a message when the authentication on the message is anonymous. In this paper, a fog-based privacy-preserving scheme is proposed to enhance the security of the vehicular crowdsensing network. Our scheme is secure with the security properties, including non-deniability, mutual authentication, integrity, forward privacy, and strong anonymity. We further analyze the designed scheme, which can not only guarantee the security requirements but also achieve higher efficiency with regards to computation and communication compared with the existing schemes.

A Survey on Tor Encrypted Traffic Monitoring

Tor (The Onion Router) is an anonymity tool that is widely used worldwide. Tor protect its user privacy against surveillance and censorship using strong encryption and obfuscation techniques which makes it extremely difficult to monitor and identify users’ activity on the Tor network. It also implements strong defense to protect the users against traffic features extraction and website fingerprinting. However, the strong anonymity also became the heaven for criminal to avoid network tracing. Therefore, numerous of research has been performed on encrypted traffic analyzing and classification using machine learning techniques. This paper presents survey on existing approaches for classification of Tor and other encrypted traffic. There is preliminary discussion on machine learning approaches and Tor network. Next, there are comparison of the surveyed traffic classification and discussion on their classification properties.

Deciding Your Own Anonymity: User-Oriented Node Selection in I2P

With the development of Internet applications, anonymous communication technology plays a very significant role in protecting personal privacy. As one of the most popular anonymous communication systems, I2P provides strong anonymity through its encryption and communication schemes. However, I2P does not consider the users’ preferences, which is difficult to meet the individual demands of specific users and then allows them to decide their anonymity. Thus, this paper proposes two novel user-oriented node selection algorithms that can effectively enhance the anonymity or reduce the communication delay over the I2P network. In order to choose proper nodes, we also investigate key factors to evaluate the nodes. Then, the basic node selection algorithm (BNSA) is proposed to group routing nodes and provide high-performance node candidates. Based on BNSA, the geographic-diversity-oriented node selection algorithm (GDNSA) and the communication-delay-oriented node selection algorithm (CDNSA) are proposed. These can improve the anonymity or communication performance of the I2P network. The GDNSA increases the attack difficulty by establishing tunnels that span multiple regions. In the meantime, the CDNSA reduces the communication delay of the tunnel by selecting the next hop node with the lowest communication delay. Finally, the mathematical analysis and experimental results show that the GDNSA has good resistance to collusion attacks, and the CDNSA reduces the communication delay in spite of weakening a little anonymity.

A secure and privacy-preserving lightweight authentication protocol for wireless communications

ABSTRACTIn wireless networks, seamless roaming allows a mobile user (MU) to utilize its services through a foreign server (FS) when outside his home server (HS). However, security and efficiency of the authentication protocol as well as privacy of MUs are of great concern to achieve an efficient authentication protocol. Conventionally, authentication involves the participation of three entities (MU, HS, and FS); however, involving an HS in the authentication process incurs heavy computational burden on it due to huge amount of roaming requests. Moreover, wireless networks are often susceptible to various forms of passive and active attacks. Similarly, mobile devices have low processing, communication, and power capabilities.In this paper, we propose an efficient, secure, and privacy-preserving lightweight authentication protocol for roaming MUs in wireless networks without engaging an HS. The proposed authentication protocol uses unlinkable pseudo-IDs and lightweight time-bound group signature to provide strong user anonymity, and a cost-effective cryptographic scheme to achieve security of the authentication protocol. Similarly, we implement a better billing system for MUs and a computationally efficient revocation scheme. Our analysis shows that the protocol has better performance than other related authentication protocols in wireless communications in terms of security, privacy, and efficiency.

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.