Accountability in Security Protocols

A promising paradigm in protocol design is to hold parties accountable for misbehavior, instead of postulating that they are trustworthy. Recent approaches in defining this property, called accountability, characterized malicious behavior as a deviation from the protocol that causes a violation of the desired security property, but did so under the assumption that all deviating parties are controlled by a single, centralized adversary. In this work, we investigate the setting where multiple parties can deviate with or without coordination in a variant of the applied-pi calculus. We first demonstrate that, under realistic assumptions, it is impossible to determine all misbehaving parties; however, we show that accountability can be relaxed to exclude causal dependencies that arise from the behavior of deviating parties, and not from the protocol as specified. We map out the design space for the relaxation, point out protocol classes separating these notions and define conditions under which we can guarantee fairness and completeness. Most importantly, we discover under which circumstances it is correct to consider accountability in the single-adversary setting, where this property can be verified with off-the-shelf protocol verification tools

Group signature revocable anonymity scheme for network monitoring

Subscriber’s Privacy is in a constant conflict with security and accountability providing controls employed for network monitoring activities of service providers and enterprises. This paper presents the results of the author’s research in the field of distributed network security monitoring architectures and the proposal of such a system that incorporates cryptographic protocols and a group signature scheme to deliver privacy protecting, network surveillance system architecture that provides subscriber’s accountability and controlled, revocable anonymity

Verifying Accountability for Unbounded Sets of Participants

Little can be achieved in the design of security protocols without trusting at least some participants. This trust should be justified; or, at the very least, subject to examination. A way of strengthening trustworthiness is to hold parties accountable for their actions, as this provides strong incentives to refrain from malicious behavior. This has lead to an increased interest in accountability in the design of security protocols. In this work, we combine the accountability definition of K\"unnemann, Esiyok, and Backes, with the notion of case tests to extend its applicability to protocols with unbounded sets of participants. We propose a general construction of verdict functions and a set of verification conditions which achieve soundness and completeness. Expressing the verification conditions in terms of trace properties allows us to extend Tamarin---a protocol verification tool---with the ability to analyze and verify accountability properties in a highly automated way. In contrast to prior work, our approach is significantly more flexible and applicable to a wide range of protocols.Comment: 40 page

AUC: Accountable Universal Composability

Accountability is a well-established and widely used security concept that allows for obtaining undeniable cryptographic proof of misbehavior, thereby incentivizing honest behavior. There already exist several general purpose accountability frameworks for formal game-based security analyses. Unfortunately, such game-based frameworks do not support modular security analyses, which is an important tool to handle the complexity of modern protocols. Universal composability (UC) models provide native support for modular analyses, including re-use and composition of security results. So far, accountability has mainly been modeled and analyzed in UC models for the special case of MPC protocols, with a general purpose accountability framework for UC still missing. That is, a framework that among others supports arbitrary protocols, a wide range of accountability properties, handling and mixing of accountable and non-accountable security properties, and modular analysis of accountable protocols. To close this gap, we propose AUC, the first general purpose accountability framework for UC models, which supports all of the above, based on several new concepts. We exemplify AUC in three case studies not covered by existing works. In particular, AUC unifies existing UC accountability approaches within a single framework

Automated Verification of Accountability in Security Protocols

Accountability is a recent paradigm in security protocol design which aims to eliminate traditional trust assumptions on parties and hold them accountable for their misbehavior. It is meant to establish trust in the first place and to recognize and react if this trust is violated. In this work, we discuss a protocol-agnostic definition of accountability: a protocol provides accountability (w.r.t. some security property) if it can identify all misbehaving parties, where misbehavior is defined as a deviation from the protocol that causes a security violation. We provide a mechanized method for the verification of accountability and demonstrate its use for verification and attack finding on various examples from the accountability and causality literature, including Certificate Transparency and Kroll’s Accountable Algorithms protocol. We reach a high degree of automation by expressing accountability in terms of a set of trace properties and show their soundness and completeness

Outsourced CP-ABE with Whitebox Accountability in IoT Systems

Cryptography based on identity and attributes enhances the chance of secure communication on a large scale. Several attribute-based encryption schemes achieve different objectives when used in various protocols. Most of these are suitable for large systems like cloud services. There are a few protocols which focus on reducing the computational overhead for lower end devices like Internet of Things sensors and actuators. It is desirable to have a mix of features in protocols for IoT security architecture. We first propose a scheme to ensure accountability in CPABE scheme FAME. The protocol is proven CPA-secure with full security in random oracle model. We also prove its accountability. We also propose a hybrid protocol that enforces user accountability and outsourced decryption in IoT systems and achieve full security in replayable chosen ciphertext attack (RCCA) under random oracle model

EFFICIENT AND SCALABLE NETWORK SECURITY PROTOCOLS BASED ON LFSR SEQUENCES

The gap between abstract, mathematics-oriented research in cryptography and the engineering approach of designing practical, network security protocols is widening. Network researchers experiment with well-known cryptographic protocols suitable for different network models. On the other hand, researchers inclined toward theory often design cryptographic schemes without considering the practical network constraints. The goal of this dissertation is to address problems in these two challenging areas: building bridges between practical network security protocols and theoretical cryptography. This dissertation presents techniques for building performance sensitive security protocols, using primitives from linear feedback register sequences (LFSR) sequences, for a variety of challenging networking applications. The significant contributions of this thesis are: 1. A common problem faced by large-scale multicast applications, like real-time news feeds, is collecting authenticated feedback from the intended recipients. We design an efficient, scalable, and fault-tolerant technique for combining multiple signed acknowledgments into a single compact one and observe that most signatures (based on the discrete logarithm problem) used in previous protocols do not result in a scalable solution to the problem. 2. We propose a technique to authenticate on-demand source routing protocols in resource-constrained wireless mobile ad-hoc networks. We develop a single-round multisignature that requires no prior cooperation among nodes to construct the multisignature and supports authentication of cached routes. 3. We propose an efficient and scalable aggregate signature, tailored for applications like building efficient certificate chains, authenticating distributed and adaptive content management systems and securing path-vector routing protocols. 4. We observe that blind signatures could form critical building blocks of privacypreserving accountability systems, where an authority needs to vouch for the legitimacy of a message but the ownership of the message should be kept secret from the authority. We propose an efficient blind signature that can serve as a protocol building block for performance sensitive, accountability systems. All special forms digital signatures—aggregate, multi-, and blind signatures—proposed in this dissertation are the first to be constructed using LFSR sequences. Our detailed cost analysis shows that for a desired level of security, the proposed signatures outperformed existing protocols in computation cost, number of communication rounds and storage overhead

Accountable to beneficiaries? : the modern development enterprise & its contractors at war : lessons on accountability from Afghanistan to inform the contracting reform agenda

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, June 2011."June 2011." Cataloged from PDF version of thesis.Includes bibliographical references (p. 85-92).This thesis will review the most relevant existing and proposed accountability mechanisms for private development and security contractors coming out of the human rights, public administration and anti-corruption fields. These three fields were selected because first, they directly shape the policy discourse around contractor accountability. Second, they each have a different emphasis or bias in their policy recommendations. Human rights advocates, for instance, are largely concerned about applying legal frameworks to and extending jurisdiction over private military and security contractors. Since private development companies by and large rely on PMSCs in lieu of adequate military security, this perspective is important to ensure development contractor accountability. Human rights discourse thus, primarily emphasizes legal accountability mechanisms. The anti-corruption field focuses on political accountability mechanisms for private contractors through initiatives to increase transparency and facilitate better governance. Lastly, public administration discourse encompasses a series of bureaucratic procedures and regulations that institutionalize accountability mechanisms through reporting, database creation, and standard operating protocols. In the human rights, anti-corruption and public administration fields, there is a cross cutting emphasis on professional accountability, whereby individual experts or firms are both internally accountable to a code of conduct and externally accountable to their peers and industry partners. But none of the existing American accountability mechanisms includes accountability to beneficiaries. Accountability is embedded within a series of relationships, whereby one party has the right to demand information, voice their opinions in a public forum and have enough leverage to impose sanctions or give rewards to another party. All present reform efforts however, continue to reinforce upwards, monetary accountability to donors, while marginalizing the ability of beneficiaries to hold private contractors accountable. The question this thesis will try to answer is: As American development projects are increasingly contracted out to private actors in conflict contexts, how should we reframe the concept and practice of "accountability" towards beneficiaries?by Huma Gupta.M.C.P

A-MAKE: an efficient, anonymous and accountable authentication framework for WMNs

In this paper, we propose a framework, named as A-MAKE, which efficiently provides security, privacy, and accountability for communications in wireless mesh networks. More specifically, the framework provides an anonymous mutual authentication protocol whereby legitimate users can connect to network from anywhere without being identified or tracked. No single party (e.g., network operator) can violate the privacy of a user, which is provided in our framework in the strongest sense. Our framework utilizes group signatures, where the private key and the credentials of the users are generated through a secure three-party protocol. User accountability is implemented via user revocation protocol that can be executed by two semitrusted authorities, one of which is the network operator. The assumptions about the trust level of the network operator are relaxed. Our framework makes use of much more efficient signature generation and verification algorithms in terms of computation complexity than their counterparts in literature, where signature size is comparable to the shortest signatures proposed for similar purposes so far