Powerful Adversary Research Articles

Powerful Adversaries

The Tax Cuts and Jobs Act of 2017 contains yet another assault on higher education in its unprecedented tax on private university endowment income. This paper argues, first, that this and other attacks should not be seen as anti-intellectual efforts to dismantle higher education but rather as intellectually elitist efforts to rid universities of certain programs and personnel and, second, that viewing these efforts as motivated primarily by racism and (hetero)sexism is an analytical and political mistake. Women’s, gender, and sexualities studies programs undermine basic assumptions that ground contemporary right-wing political and economic policy—namely, individualism and economism—by presenting empirical evidence and developing theoretical frameworks focused on historical formations of power networks that produce subjects, preferences, and systems of oppression. The main goal of the radical right is not to purge women and people of color from academia, but to prevent analysis and discussion that reveals the inadequacy of right-wing ontological commitments and neoliberal social theory.

Asynchronous approach in the plane: a deterministic polynomial algorithm

In this paper we study the task of approach of two mobile agents having the same limited range of vision and moving asynchronously in the plane. This task consists in getting them in finite time within each other’s range of vision. The agents execute the same deterministic algorithm and are assumed to have a compass showing the cardinal directions as well as a unit measure. On the other hand, they do not share any global coordinates system (like GPS), cannot communicate and have distinct labels. Each agent knows its label but does not know the label of the other agent or the initial position of the other agent relative to its own. The route of an agent is a sequence of segments that are subsequently traversed in order to achieve approach. For each agent, the computation of its route depends only on its algorithm and its label. An adversary chooses the initial positions of both agents in the plane and controls the way each of them moves along every segment of the routes, in particular by arbitrarily varying the speeds of the agents. Roughly speaking, the goal of the adversary is to prevent the agents from solving the task, or at least to ensure that the agents have covered as much distance as possible before seeing each other. A deterministic approach algorithm is a deterministic algorithm that always allows two agents with any distinct labels to solve the task of approach regardless of the choices and the behavior of the adversary. The cost of a complete execution of an approach algorithm is the length of both parts of route travelled by the agents until approach is completed. Let Δ and l be the initial distance separating the agents and the length of (the binary representation of) the shortest label, respectively. Assuming thatΔandlare unknown to both agents, does there exist a deterministic approach algorithm always working at a cost that is polynomial inΔandl? Actually the problem of approach in the plane reduces to the network problem of rendezvous in an infinite oriented grid, which consists in ensuring that both agents end up meeting at the same time at a node or on an edge of the grid. By designing such a rendezvous algorithm with appropriate properties, as we do in this paper, we provide a positive answer to the above question. Our result turns out to be an important step forward from a computational point of view, as the other algorithms allowing to solve the same problem either have an exponential cost in the initial separating distance and in the labels of the agents, or require each agent to know its starting position in a global system of coordinates, or only work under a much less powerful adversary.

Device independence for two-party cryptography and position verification with memoryless devices

Quantum communication has demonstrated its usefulness for quantum cryptography far beyond quantum key distribution. One domain is two-party cryptography, whose goal is to allow two parties who may not trust each other to solve joint tasks. Another interesting application is position-based cryptography whose goal is to use the geographical location of an entity as its only identifying credential. Unfortunately, security of these protocols is not possible against an all powerful adversary. However, if we impose some realistic physical constraints on the adversary, there exist protocols for which security can be proven, but these so far relied on the knowledge of the quantum operations performed during the protocols. In this work we give device-independent security proofs of two-party cryptography and Position Verification for memoryless devices under different physical constraints on the adversary. We assess the quality of the devices by observing a Bell violation and we show that security can be attained for any violation of the Clauser-Holt-Shimony-Horne inequality.

Latent-Data Privacy Preserving With Customized Data Utility for Social Network Data

Social network data can help with obtaining valuable insight into social behaviors and revealing the underlying benefits. New big data technologies are emerging to make it easier to discover meaningful social information from market analysis to counterterrorism. Unfortunately, both diverse social datasets and big data technologies raise stringent privacy concerns. Adversaries can launch inference attacks to predict sensitive latent information, which is unwilling to be published by social users. Therefore, there is a tradeoff between data benefits and privacy concerns. In this paper, we investigate how to optimize the tradeoff between latent-data privacy and customized data utility. We propose a data sanitization strategy that does not greatly reduce the benefits brought by social network data, while sensitive latent information can still be protected. Even considering powerful adversaries with optimal inference attacks, the proposed data sanitization strategy can still preserve both data benefits and social structure, while guaranteeing optimal latent-data privacy. To the best of our knowledge, this is the first work that preserves both data benefits and social structure simultaneously and combats against powerful adversaries.

Bootstrapping trust in software defined networks

Software-Defined Networking (SDN) is a novel architectural model for cloud network infrastructure, improving resource utilization, scalability and administration. SDN deployments increasingly rely on virtual switches executing on commodity operating systems with large code bases, which are prime targets for adversaries attacking the network infrastructure. We describe and implement TruSDN, a framework for bootstrapping trust in SDN infrastructure using Intel Software Guard Extensions (SGX), allowing to securely deploy SDN components and protect communication between network endpoints. We introduce ephemeral flow-specific preshared keys and propose a novel defense against cuckoo attacks on SGX enclaves. TruSDN is secure under a powerful adversary model, with a minor performance overhead. (Less)

User-friendly deniable storage for mobile devices

Mobile devices are prevalently used to process sensitive data, but traditional encryption may not work when an adversary is able to coerce the device owners to disclose the encryption keys. Plausibly Deniable Encryption (PDE) is thus designed to protect sensitive data against this powerful adversary. In this paper, we present MobiPluto, a user-friendly PDE scheme for denying the existence of sensitive data stored on mobile devices. A salient difference between MobiPluto and the existing PDE systems is that any block-based file systems can be deployed on top of it. To further improve usability and deniability of MobiPluto, we introduce a fast switching mechanism and incorporate the widely-used Near Field Communication (NFC) technology. Users can securely switch from the public mode to the hidden mode within 10 seconds, which is a significant improvement compared to previous solutions. Users can also store strong passwords on NFC cards and tap them to enter the system, which significantly liberates them from the burden of memorizing and typing strong passwords. Most importantly, the users can deny the existence of the hidden data without the skill to camouflage as long as the NFC cards are used properly.

Online-bounded analysis

Though competitive analysis is often a very good tool for the analysis of online algorithms, sometimes it does not give any insight and sometimes it gives counter-intuitive results. Much work has gone into exploring other performance measures, in particular targeted at what seems to be the core problem with competitive analysis: The comparison of the performance of an online algorithm is made with respect to a too powerful adversary. We consider a new approach to restricting the power of the adversary, by requiring that when judging a given online algorithm, the optimal offline algorithm must perform at least as well as the online algorithm, not just on the entire final request sequence, but also on any prefix of that sequence. This is limiting the adversary’s usual advantage of being able to exploit that it knows the sequence is continuing beyond the current request. Through a collection of online problems, including machine scheduling, bin packing, dual bin packing, and seat reservation, we investigate the significance of this particular offline advantage.

DataLair: Efficient Block Storage with Plausible Deniability against Multi-Snapshot Adversaries

Abstract Sensitive information is present on our phones, disks, watches and computers. Its protection is essential. Plausible deniability of stored data allows individuals to deny that their device contains a piece of sensitive information. This constitutes a key tool in the fight against oppressive governments and censorship. Unfortunately, existing solutions, such as the now defunct TrueCrypt [5], can defend only against an adversary that can access a user’s device at most once (“single-snapshot adversary”). Recent solutions have traded significant performance overheads for the ability to handle more powerful adversaries able to access the device at multiple points in time (“multi-snapshot adversary”). In this paper we show that this sacrifice is not necessary. We introduce and build DataLair1, a practical plausible deniability mechanism. When compared with existing approaches, DataLair is two orders of magnitude faster for public data accesses, and 5 times faster for hidden data accesses. An important component in DataLair is a new write-only ORAM construction which improves on the complexity of the state of the art write-only ORAM by a factor of O(logN), where N denotes the underlying storage disk size.

A CRT‐based verifiable secret sharing scheme secure against unbounded adversaries

AbstractFor commitments on secrets, statistical hiding is a must when we are dealing with a long‐term secret or when the secret domain is small enough for a brute‐force attack by a powerful adversary. Unfortunately, all the Chinese Remainder Theorem‐based verifiable secret sharing schemes in the literature are either insecure or suffer from the vulnerability of computationally hiding commitments. To the best of our knowledge, there exist five such studies where two of them were already proven to be insecure. In this work, we first show that two of the remaining schemes are also insecure, that is, the schemes reveal information on the secret even when the adversary is passive. In addition, the remaining one is only secure against a computationally bounded adversary which can be a problem for secret sharing schemes requiring long‐term secret obscurity or using small secret domain. We propose a modification for the latter scheme and prove that the modified scheme is a secure verifiable secret sharing scheme against an unbounded adversary. Lastly, as an application, we show how to use the new scheme for joint random secret sharing and analyze the practicality and efficiency of the proposed schemes. Copyright © 2016 John Wiley & Sons, Ltd.

Privacy Secured and Share with the Destination in Cloud

Cloud computing refers to applications and services that run on a distributed network using virtualized resources and accessed by common Internet protocols and networking standards. Cloud computing takes the technology, services, and applications that are similar to those on the Internet and turns them into a self-service utility. Without adequate privacy protection, the system can be easily misused, e.g., to track users target them for home invasion. introduce LocX, a novel alternative that provides significantly-improved location privacy without adding uncertainty into query results or relying on strong assumptions about server security. Our key aim is to apply secure user- specific, distance-preserving coordinate transformations to all location data shared with the server. The friends of a user share this user's secrets, so they can apply the same transformation to destination. This allows all location queries to be evaluated correctly by the server, but our privacy mechanisms guarantee that servers are unable to see or infer the actual location data from the transformed data or from the data access. show that LocX provides privacy even against a powerful adversary model, and we use prototype measurements to show that it provides privacy with very little performance overhead, making it suitable for today's mobile devices.

Efficient Post-Quantum Secure Network Coding Signatures in the Standard Model

In contrast to traditional “store-and-forward” routing mechanisms, network coding offers an elegant solution for achieving maximum network throughput. The core idea is that intermediate network nodes linearly combine received data packets so that the destination nodes can decode original files from some authenticated packets. Although network coding has many advantages, especially in wireless sensor network and peer-to-peer network, the encoding mechanism of intermediate nodes also results in some additional security issues. For a powerful adversary who can control arbitrary number of malicious network nodes and can eavesdrop on the entire network, cryptographic signature schemes provide undeniable authentication mechanisms for network nodes. However, with the development of quantum technologies, some existing network coding signature schemes based on some traditional number-theoretic primitives vulnerable to quantum cryptanalysis. In this paper we first present an efficient network coding signature scheme in the standard model using lattice theory, which can be viewed as the most promising tool for designing post-quantum cryptographic protocols. In the security proof, we propose a new method for generating a random lattice and the corresponding trapdoor, which may be used in other cryptographic protocols. Our scheme has many advantages, such as supporting multi-source networks, low computational complexity and low communication overhead.

David versus Goliath: Risk and Weaker State Confrontation

Confronting a more powerful rival can be a risky proposition. This paper integrates prospect theory into the growing Neoclassical Realist (NCR) literature to identify the conditions under which decision makers are most likely to accept foreign policy risks. I argue that decision makers governing regimes with low levels of political counterframing are more likely to settle into a dominant loss frame when their external security environment erodes. This increases the probability that they will initiate disputes with more powerful adversaries. To assess this proposition, I conduct a test of weaker state confrontation grounded in a NCR framework that utilizes the insights from prospect theory. Data come from the postwar era and support my hypothesis. Loss frames exert influence over the decision to initiate risky foreign policy strategies in regimes in which political counterframing is absent.

Semiquantum key distribution with secure delegated quantum computation.

Semiquantum key distribution allows a quantum party to share a random key with a “classical” party who only can prepare and measure qubits in the computational basis or reorder some qubits when he has access to a quantum channel. In this work, we present a protocol where a secret key can be established between a quantum user and an almost classical user who only needs the quantum ability to access quantum channels, by securely delegating quantum computation to a quantum server. We show the proposed protocol is robust even when the delegated quantum server is a powerful adversary, and is experimentally feasible with current technology. As one party of our protocol is the most quantum-resource efficient, it can be more practical and significantly widen the applicability scope of quantum key distribution.

Quantum-secure covert communication on bosonic channels.

Computational encryption, information-theoretic secrecy and quantum cryptography offer progressively stronger security against unauthorized decoding of messages contained in communication transmissions. However, these approaches do not ensure stealth—that the mere presence of message-bearing transmissions be undetectable. We characterize the ultimate limit of how much data can be reliably and covertly communicated over the lossy thermal-noise bosonic channel (which models various practical communication channels). We show that whenever there is some channel noise that cannot in principle be controlled by an otherwise arbitrarily powerful adversary—for example, thermal noise from blackbody radiation—the number of reliably transmissible covert bits is at most proportional to the square root of the number of orthogonal modes (the time-bandwidth product) available in the transmission interval. We demonstrate this in a proof-of-principle experiment. Our result paves the way to realizing communications that are kept covert from an all-powerful quantum adversary.

Publishable Humanly Usable Secure Password Creation Schemas

What can a human compute in his/her head that a powerful adversary cannot infer? To answer this question, we define a model of human computation and a measure of security. Then, motivated by the special case of password creation, we propose a collection of well-defined password-generation methods. We show that our password generation methods are humanly computable and, to a well-defined extent, machine uncrackable. For the proof of security, we posit that password generation methods are public, but that the human’s privately chosen seed is not, and that the adversary will have observed only a few input-output pairs. Besides the application to password generation, our proposed Human Usability Model (HUM) will have other applications.

Rights, citizenship and political struggle

This paper adds a new perspective to recent debates about the political nature of rights through attention to their distinctive role within social movement practices of moral critique and social struggle. The paper proceeds through a critical examination of the Political Constitutionalist theories of rights politics proposed by Jeremy Waldron and Richard Bellamy. While political constitutionalists are correct to argue that rights are ‘contestable’ and require democratic justification, they construe political activity almost exclusively with reference to voting, parties and parliamentary law-making, neglecting the vital role rights play in political struggle outside and against the official institutions of democratic citizenship. In contrast to the political constitutionalist stress on the patient and reciprocal negotiation of rights within formal electoral processes, this paper locates the political nature of rights in their conflictual logic as ‘claims’ in multiple spheres that function to mobilise oppositional support against powerful adversaries and challenge dominant understandings. An activist citizenship of rights is frequently necessary, it argues, given the structural barriers of power and inequality that distort legislative decision-making and lead to the denial of fundamental moral entitlements to less powerful groups. The paper provides an illustration of activist citizenship taken from a contemporary squatting movement centred around the right to housing, Take Back the Land. In exercising the moral right to housing, for which they demand political recognition, through the occupation of vacant buildings, the practices of Take Back the Land reflect the conflictual dimension of rights as claims in keeping with their historical role in empowering subordinate groups to challenge unjust relations of power and inequality.

The re-emergence of asymmetric labour relations: two campaigns that have abandoned traditional labour tactics in favour of community organising

Employee voice in English-speaking jurisdictions is often characterised as being exercised via union or non-union channels. The present terrain has come about as a result of more than three decades of the gradual fragmentation of work forms and a related decline in union voice. This nomenclature does not account for the emergence of forms of voice that blur this distinction: third-party worker advocacy which may be led by unions or by other groups. Relative to mass membership unions, these groups are characterised by a paucity of resources and often an open, network organisational structure instead of a hierarchical structure, leading to inclusion of non-labour community groups and a broadening of their agenda beyond traditional workplace relation matters. This paper borrows the notion of asymmetry to explain the success of these groups when facing much more powerful adversaries. Two case studies are examined in detail, both in the retail industry.

An Authenticated Key Agreement Scheme for Wireless Sensor Networks

We propose a new authenticated key agreement scheme based on Blom’s scheme, but using multiple master keys and public keys in permutations to compute the private keys in each node. The computations are over a small prime field, and by storing them in a random order in the node, the private-public-master-key associations (PPMka) of the private keys are lost. If a node is captured, the PPMka of the private keys cannot be determined with certainty, making it difficult to begin to attack the scheme. We obtained analytical results to show that, using suitable keying parameters, the probability of discovering the correct PPMka can be made so small, that a very powerful adversary needs to capture the entire network of tens of thousands of nodes or expend an infeasible amount of effort to try all of the possible solutions. We verified our results using computer-simulated attacks on the scheme. The unknown PPMka enables our scheme to break free from the capture threshold of the original Blom’s scheme, so that it can be used in large networks of low-resource devices, such as sensor nodes.

On the complexity of asynchronous agreement against powerful adversaries

We introduce new techniques for proving lower bounds on the running time of randomized algorithms for asynchronous agreement against powerful adversaries. In particular, we define a strongly adaptive adversary that is computationally unbounded and has a limited ability to corrupt a dynamic subset of processors by erasing their memories. We demonstrate that the randomized agreement algorithms designed by Ben-Or and Bracha to tolerate crash or Byzantine failures in the asynchronous setting extend to defeat a strongly adaptive adversary. These algorithms have essentially perfect correctness and termination, but at the expense of exponential running time. In the case of the strongly adaptive adversary, we show that this dismally slow running time is inherent: we prove that any algorithm with essentially perfect correctness and termination against the strongly adaptive adversary must have exponential running time. We additionally interpret this result as yielding an enhanced understanding of the tools needed to simultaneously achieving perfect correctness and termination as well as fast running time for randomized algorithms tolerating crash or Byzantine failures.

Performing private database queries in a real-world environment using a quantum protocol.

In the well-studied cryptographic primitive 1-out-of-N oblivious transfer, a user retrieves a single element from a database of size N without the database learning which element was retrieved. While it has previously been shown that a secure implementation of 1-out-of-N oblivious transfer is impossible against arbitrarily powerful adversaries, recent research has revealed an interesting class of private query protocols based on quantum mechanics in a cheat sensitive model. Specifically, a practical protocol does not need to guarantee that the database provider cannot learn what element was retrieved if doing so carries the risk of detection. The latter is sufficient motivation to keep a database provider honest. However, none of the previously proposed protocols could cope with noisy channels. Here we present a fault-tolerant private query protocol, in which the novel error correction procedure is integral to the security of the protocol. Furthermore, we present a proof-of-concept demonstration of the protocol over a deployed fibre.