In identity federations, users assigned to identity providers (IDPs) can access applications operated by service providers (SPs) without SP-specific credentials for authentication and authorization. While OpenID Connect and SAML are the two most widely adopted federation standards, using them inherently results in a trade-off between data quality guarantees and scalability, given how they handle the Metadata about the involved IDPs and SPs. This paper presents a novel approach for federation membership and federation Metadata management based on Distributed Ledger Technology. It applies the core idea of Certificate Transparency, as known from Global-PKI certificate authorities for X.509v3 server certificates, to SAML federation Metadata; therefore, it achieves OpenID Connect's federation building flexibility without losing the significant advantages of traditional SAML federations. An implementation based on Hyperledger Fabric is used to evaluate typical use cases by measuring impacts on Metadata distribution latency and Metadata size, and to discuss the feasibility of the presented approach.
This paper investigates a critical access control issue in the Internet of Things (IoT). In particular, we propose a smart contract-based framework, which consists of multiple access control contracts (ACCs), one judge contract (JC), and one register contract (RC), to achieve distributed and trustworthy access control for IoT systems. Each ACC provides one access control method for a subject-object pair, and implements both static access right validation based on predefined policies and dynamic access right validation by checking the behavior of the subject. The JC implements a misbehavior-judging method to facilitate the dynamic validation of the ACCs by receiving misbehavior reports from the ACCs, judging the misbehavior and returning the corresponding penalty. The RC registers the information of the access control and misbehavior-judging methods as well as their smart contracts, and also provides functions (e.g., register, update, and delete) to manage these methods. To demonstrate the application of the framework, we provide a case study in an IoT system with one desktop computer, one laptop and two Raspberry Pi single-board computers, where the ACCs, JC, and RC are implemented based on the Ethereum smart contract platform to achieve the access control.
Hany F. Atlam, Ahmed Alenezi, Raid Khalid Hussein, Gary Wills
The Internet of Things (IoT) has spread into multiple dimensions that incorporate different physical and virtual things. These things are connected together using different communication technologies to provide unlimited services. These services help not only to improve the quality of our daily lives, but also to provide a communication platform for increasing object collaboration and information sharing. Like all new technologies, the IoT has many security challenges that stand as a barrier to the successful implementation of IoT applications. These challenges are more complicated due to the dynamic and heterogeneous nature of IoT systems. However, authentication and access control models can be used to address the security issue in the IoT. To increase information sharing and availability, the IoT requires a dynamic access control model that takes not only access policies but also real-time contextual information into account when making access decisions. One of the dynamic features is the security risk. This paper proposes an Adaptive Risk-Based Access Control (AdRBAC) model for the IoT and discusses its validation using expert reviews. The proposed AdRBAC model conducts a risk analysis to estimate the security risk value associated with each access request when making an access decision. This model has four inputs/risk factors: user context, resource sensitivity, action severity and risk history. These risk factors are used to estimate a risk value associated with the access request to make the access decision. To provide the adaptive features, smart contracts will be used to monitor the user behaviour during access sessions to detect any malicious actions from the granted users. To validate and refine the proposed model, twenty IoT security experts from inside and outside the UK were interviewed. The experts have suggested valuable information that will help to specify the appropriate risk factors and risk estimation technique for implantation of the AdRBAC model.
Patrick Mangesius, Johannes Bachmann, Thomas Healy, Samrend Saboor · 5 authors
INTRODUCTION: Interoperability of health information systems is one of the key challenges of modern healthcare systems. A weak spot in this technology stack of interoperability protocols as defined by HL7 and IHE is cross affinity domain exchange of access control information and policies. In several industries the Blockchain technology had a major breakthrough. The goal of this paper is to elaborate how to exchange cross affinity domain access information enhancing well established IHE networks with block chain technology. METHODS: Using literature analysis and research on current interoperability standards the state of the art of securely exchanging medical information was elaborated. We enhanced this system with the capabilities of the peer2peer based Blockchain network elaborating the workflows of exchanging the access control specific information. RESULTS: We extended an IHE based affinity domain by adding a block chain ledger to the deployment. This ledger is fed with XACML based policies which are propagated through the peer2peer based system. Using the Blockchain protocol other affinity domains are informed of the change and can retrieve the information. Acting as an additional source of policies and consents the policy decision point is capable of querying this network and building a decision based on the retrieved information.
Blockchain technology is expected to be an enabler of Ëtrust-free economic transactionsâ¢, which implies a frictionless economy without uncertainty and risks. Looking at current use cases of blockchains such as the peer-to-peer payment system Bitcoin, it i
Throughout the history of mankind, trusted relationships have played a vital part in every \ntransaction humans have made. Those transactions belong to a spectrum that starts from \neveryday life decisions and acts, to a more complex, sensitive and wide area that even nations \nare involved. \nBefore the era of globalization of telecommunications that we live in, achieving trust was \nmore related to human relations. Even though that the meaning of trust is known to all, it is \nhard to find a definition that strictly describes it. \nTrust is multidimensional, multidisciplinary and multifaceted concept. Many definitions can \nbe found in literature and are related to notions as goodness, strength, reliability, integrity, \nability or character of a person or thing. A trust relationship involves two parties, a trustor \nand a trustee. The trustor is the person that holds confidence, belief on the reliability of \nanother person or thing which is the other party, the trustee. (Zheng & Valtteri Niemi, \nTowards User Driven Trust Modeling and Management, 2009) \nHow though trust is established in modern computer networks, where the notions of the \ntrustor and trustee are not represented by strictly humans, but from entities that might never \nhave had a relationship upon the trust can be build. \nIn this project we will study the achievement of trust in traditional kinds of networks such as \nad-hoc, mobile and wireless and we will examine the ability to elevate the trust level in a \ncomputer network using the under development and mostly promising blockchain network. \nThe network is going to be setup as a private blockchain network, where all the nodes that \nconsist it, will be pre-set from an administrative team. The computers that will participate will \nhave all the requirements in order to connect to the private network running as services on \nboot. \nThe application will run on each node and on starting the application the very first check will \nbe to start the node and connect to the network. Only if the network has been found and the \nnode is connected to it, the application proceeds with checking the presence of web3js and \nonly after successfully checking the communication of the web3js with the network, the user \nis prompt with the login page. \nThe authorization of the user is checked upon a smart contract on the blockchain network \nand after a successfully prompt from the smart contract, the credentials are checked, in our \ncase, on a fake backend where a JWT token is issued to the user in order to use the application \ndepending on the role that he has.
We introduce BitML, a domain-specific language for specifying contracts that regulate transfers of bitcoins among participants, without relying on trusted intermediaries. We define a symbolic and a computational model for reasoning about BitML security. In the symbolic model, participants act according to the semantics of BitML, while in the computational model they exchange bitstrings, and read/append transactions on the Bitcoin blockchain. A compiler is provided to translate contracts into standard Bitcoin transactions. Participants can execute a contract by appending these transactions on the Bitcoin blockchain, according to their strategies. We prove the correctness of our compiler, showing that computational attacks on compiled contracts are also observable in the symbolic model.
Ilaria Bertazzi, Sylvie Huet, Guillaume Deffuant, Floriana Gargiulo
Bitcoin-otc is a peer to peer (over-the-counter) marketplace for trading with bit- coin crypto-currency. To mitigate the risks of the p2p unsupervised exchanges, the establishment of a reliable reputation systems is needed: for this reason, a web of trust is implemented on the website. The availability of all the historic of the users interaction data makes this dataset a unique playground for studying reputation dynamics through others evaluations. We analyze the structure and the dynamics of this web of trust with a multilayer network approach distin- guishing the rewarding and the punitive behaviors. We show that the rewarding and the punitive behavior have similar emergent topological properties (apart from the clustering coefficient being higher for the rewarding layer) and that the resultant reputation originates from the complex interaction of the more regular behaviors on the layers. We show which are the behaviors that correlate (i.e. the rewarding activity) or not (i.e. the punitive activity) with reputation. We show that the network activity presents bursty behaviors on both the layers and that the inequality reaches a steady value (higher for the rewarding layer) with the network evolution. Finally, we characterize the reputation trajectories and we identify prototypical behaviors associated to three classes of users: trustworthy, untrusted and controversial.
Public-key infrastructures (PKIs) are an integral part of the security foundations of digital communications. Their widespread deployment has allowed the growth of important applications, such as, internet banking and e-commerce. Centralized PKIs (CPKIs) rely on a hierarchy of trusted Certification Authorities (CAs) for issuing, distributing and managing the status of digital certificates, i.e., unforgeable data structures that attest to the authenticity of an entity’s public key. Unfortunately, CPKI’s have many downsides in terms of security and fault tolerance and there have been numerous security incidents throughout the years. Decentralized PKIs (DPKIs) were proposed to deal with these issues as they rely on multiple, independent nodes. Nevertheless, decentralization raises other concerns such as what are the incentives for the participating nodes to ensure the service’s availability.
The role-based access control (RBAC) framework is a mechanism that describes the access control principle. As a common interaction, an organization provides a service to a user who owns a certain role that was issued by a different organization. Such trans-organizational RBAC is common in face-toface communication but not in a computer network, because it is difficult to establish both the security that prohibits the malicious impersonation of roles and the flexibility that allows small organizations to participate and users to fully control their own roles. In this paper, we present an RBAC using smart contract (RBAC-SC), a platform that makes use of Ethereum's smart contract technology to realize a trans organizational utilization of roles. Ethereum is an open blockchain platform that is designed to be secure, adaptable, and flexible. It pioneered smart contracts, which are decentralized applications that serve as “autonomous agents”running exactly as programmed and are deployed on a blockchain. The RBAC-SC uses smart contracts and blockchain technology as versatile infrastructures to represent the trust and endorsement relationship that are essential in the RBAC and to realize a challenge-response authentication protocol that verifies a user's ownership of roles. We describe the RBAC-SC framework, which is composed of two main parts, namely, the smart contract and the challenge-response protocol, and present a performance analysis. A prototype of the smart contract is created and deployed on Ethereum's Testnet blockchain, and the source code is publicly available.
Christian Badertscher, Sandro Coretti, Chen-Da Liu-Zhang, Ueli Maurer
Commitment schemes that admit zero-knowledge proofs for relations among committed values are known as commit-and-prove functionalities or notarized envelopes. An important role in this context play equality proofs among commitments. They appear in various contexts of multi-party computation, circuit satisfiability or inclusion proofs. Using commit- and-prove functionalities admitting equality, we investigate blackbox constructions of commit-and-prove functionalities admitting more complex relations. Typically, these constructions have to create commitments to additional values to achieve a certain level of soundness. An important efficiency measure is the number of such additional commitments. We prove that, for the natural and quite general class of 3-round public-coin zero-knowledge protocols, implementing the inequality relation, or any of the relations NAND, NOR, or XOR, essentially requires at least 2n additional commitments in order to achieve a soundness of 2-n. A folklore protocol shows that this bound is tight for inequality.
In the Big Data era, personal metadata may will become a new type of corporate asset, however there have already been a growing public concern about user's privacy mined from metadata. In this paper we address the problem of implementing the self-sovereignty of personal metadata on the existing OpenPDS/SafeAnswers framework according to the Windhover Principle. In order to do that, we propose a new framework, called BlocakChain-based Personal Data Store (BCPDS), to realize two basic properties: notary and autonomy. This framework, firstly introduces the BlockChain as a notary, into OpenPDS/SafeAnswers for secure storage of personal meta-data instead of the original database. Next, we present an AutoNomybased Access Control (ANAC) to improve the SafeAnswers module, where ANAC is a new mechanism that enforces access based on the relationship among all authorized users and metadata's owner. In addition, we also propose General Access Structure (GAS) and threshold secret sharing scheme in BlockChain as an implementation method for our BC-PDS framework.
Yupeng Zhang, Jonathan Katz, Charalampos Papamanthou
We present a new construction of an expressive set accumulator. Unlike existing cryptographic accumulators, ours provides succinct proofs for a large collection of operations over accumulated sets, including intersection, union, set difference, SUM, COUNT, MIN, MAX, and RANGE, as well as arbitrary nestings of the above. We also show how to extend our accumulator to be zero-knowledge. The security of our accumulator is based on extractability assumptions and other assumptions that hold in the generic group model. Our construction has asymptotically optimal verification complexity and proof size, constant update complexity, and public verifiability/updatability-namely, any client who knows the public key and the last accumulator value can verify the supported operations and update the accumulator. The expressiveness of our accumulator comes at the cost of quadratic prover time. However, we show that the cryptographic operations involved are cheap compared to those incurred by generic approaches (e.g., SNARKs) that are equally expressive: our prover runs faster for sets of up to 5 million items. Our accumulator serves as a powerful cryptographic tool with many applications. For example, it can be applied to efficiently support verification of a rich collection of SQL queries when used as a drop-in replacement in existing verifiable database systems (e.g., IntegriDB, CCS 2015).
Hubert Ritzdorf, Karl Wüst, Arthur Gervais, Guillaume Felley · 5 authors
An internet user wanting to share observed content is typically restricted to primitive techniques such as screenshots, web caches or share button-like solutions. These acclaimed proofs, however, are either trivial to falsify or require trust in centralized entities (e.g., search engine caches). This motivates the need for a seamless and standardized internet-wide non-repudiation mechanism, allowing users to share data from news sources, social websites or financial data feeds in a provably secure manner. Additionally, blockchain oracles that enable data-rich smart contracts typically rely on a trusted third party (e.g., TLSNotary or Intel SGX). A decentralized method to transfer web-based content into a permissionless blockchain without additional trusted third party would allow for smart contract applications to flourish. In this work, we present TLS-N, the first TLS extension that provides secure non-repudiation and solves both of the mentioned challenges. TLS-N generates non-interactive proofs about the content of a TLS session that can be efficiently verified by third parties and blockchain based smart contracts. As such, TLS-N increases the accountability for content provided on the web and enables a practical and decentralized blockchain oracle for web content. TLS-N is compatible with TLS 1.3 and adds a minor overhead to a typical TLS session. When a proof is generated, parts of the TLS session (e.g., passwords, cookies) can be hidden for privacy reasons, while the remaining content can be verified.
Lei Xu, Lin Chen, Nolan Shah, Zhimin Gao · 6 authors
Since Internet based applications have become the norm for most users, security has become a bigger concern than ever before, especially for applications like social networking and cloud based storage. Access control is one of the key techniques that can mitigate security concerns for web based applications. However, most existing access control mechanisms require a trusted party, which are vulnerable to many threats including malicious insiders and single point failure. In response to these challenges, we propose DL-BAC, a novel access control system based on the distributed ledger. DL-BAC robustly enforces access control policies without depending on a single trusted party. We also provide an extension of DL-BAC that is privacy respecting and evaluate the performance of DL-BAC to show its practicability.
Aissam Outchakoucht, Hamza Es-Samaali, Jean Philippe
The Internet of Things (IoT) is now destroying the barriers between the real and digital worlds. However, one of the huge problems that can slow down the development of this global wave, or even stop it, concerns security and privacy requirements. The criticality of these latter comes especially from the fact that the smart objects may contain very intimate information or even may be responsible for protecting people’s lives. In this paper, the focus is on access control in the IoT context by proposing a dynamic and fully distributed security policy. Our proposal will be based, on one hand, on the concept of the blockchain to ensure the distributed aspect strongly recommended in the IoT; and on the other hand on machine learning algorithms, particularly on reinforcement learning category, in order to provide a dynamic, optimized and self-adjusted security policy.
Unlinkability and accountability are conflicting yet critical requirements that need to be addressed in order to preserve users' privacy as well as to protect service providers in today identity ecosystems. In this paper we present a pseudonymous identity management system in which users can carry out unlinkable on-line transactions without having to disclose their actual identity information in plain text to the service providers. At the same time, the service providers have strong assurance about the authenticity of the transactions. In our approach, users' identity is cryptographically encoded in pseudonymous identity tokens. % issued by trusted identity providers. Our system includes a lightweight policy language which enables users and service providers to express their requirements pertaining to pseudonymous identity verification and a suite of protocols based on zero-knowledge-proofs which enables the fulfillment of these requirements. We have implemented a prototype of the proposed system and carried out a security and performance analysis.
There has recently been a flood of interest in potential new applications of blockchains, as well as proposals for more generic designs called public ledgers. Most of the novel proposals have been in the financial sector. However, the public ledger is an abstraction that solves several of the fundamental problems in the design of secure distributed systems: global time in the form of a strict linear order of past events, globally consistent and immutable view of the history, and enforcement of some application-specific safety properties. This paper investigates the applications of public ledgers to access control and, more specifically, to group management in distributed systems where entities are represented by their public keys and authorization is encoded into signed certificates. It is particularly difficult to handle negative information, such as revocation of certificates or group membership, in the distributed setting. The linear order of events and global consistency simplify these problems, but the enforcement of internal constraints in the ledger implementation often presents problems. We show that different types of revocation require slightly different properties from the ledger. We compare the requirements with Bitcoin, the best known blockchain, and describe an efficient ledger design for membership revocation that combines ideas from blockchains and from web-PKI monitoring. While we use certificate-based group-membership management as the case study, the same ideas can be applied more widely to rights revocation in distributed systems.
There has recently been a flood of interest in potential new applications of\nblockchains, as well as proposals for more generic designs called public\nledgers. Most of the novel proposals have been in the financial sector.\nHowever, the public ledger is an abstraction that solves several of the\nfundamental problems in the design of secure distributed systems: global time\nin the form of a strict linear order of past events, globally consistent and\nimmutable view of the history, and enforcement of some application-specific\nsafety properties. This paper investigates the applications of public ledgers\nto access control and, more specifically, to group management in distributed\nsystems where entities are represented by their public keys and authorization\nis encoded into signed certificates. It is particularly difficult to handle\nnegative information, such as revocation of certificates or group membership,\nin the distributed setting. The linear order of events and global consistency\nsimplify these problems, but the enforcement of internal constraints in the\nledger implementation often presents problems. We show that different types of\nrevocation require slightly different properties from the ledger. We compare\nthe requirements with Bitcoin, the best known blockchain, and describe an\nefficient ledger design for membership revocation that combines ideas from\nblockchains and from web-PKI monitoring. While we use certificate-based\ngroup-membership management as the case study, the same ideas can be applied\nmore widely to rights revocation in distributed systems.\n