Wireless handheld devices are increasingly popular. The authenticity of the information or a program to be downloaded is important, especially for business uses. In server-aided verification (SAV), a substantial part of the verification computation can be offloaded to an untrusted server. This allows resource-constrained devices to enjoy the security guarantees provided by cryptographic schemes, such as pairing-based signatures, which may be too heavyweight to verify otherwise.To gain unfair advantage, an adversary may bribe (or collude with) the server either to convince that an invalid signature is a valid one or to claim that a valid signature is invalid (say for providing repudiable information/commitment, or spoiling an opponent's offer). However, these concerns are not properly captured by existing models.In this paper, we infer the meaning behind and point out the subtleties in existing models; and propose a new model to capture the collusion attack. We also show that two existing schemes are insecure in their own model. Finally, we provide a generic pairing-based SAV protocol. Compared with the protocol of Girault–Lefranc in Asiacrypt '05, ours provides a higher level of security yet applicable to a much wider class of pairing-based cryptosystems. In particular, it suggests SAV protocols for short signatures in the standard model and aggregate signatures which have not been studied before.
As the world becomes an interconnected network where objects and humans interact with each other, new challenges and threats appear in the ecosystem. In this interconnected world, smart objects have an important role in giving users the chance for life-logging in smart environments. However, smart devices have several limitations with regards to memory, resources and computation power, hindering the opportunity to apply well-established security algorithms and techniques for secure life-logging on the Internet of Things (IoT) domain. The need for secure and trustworthy life-logging in smart environments is vital, thus, a lightweight approach has to be considered to overcome the constraints of Smart Objects. The purpose of this paper is to present in details the current topics of life-logging in smart environments, while describing interconnection issues, security threats and suggesting a lightweight framework for ensuring security, privacy and trustworthy life-logging. In order to investigate the efficiency of the lightweight framework and the impact of the security attacks on energy consumption, an experimental test-bed was developed including two interconnected users and one smart attacker, who attempts to intercept transmitted messages or interfere with the communication link. Several mitigation factors, such as power control, channel assignment and AES-128 encryption were applied for secure life-logging. Finally, research into the degradation of the consumed energy regarding the described intrusions is presented.
The use of role engineering has grown in importance with the expansion of highly abstracted access control frameworks in organizations. In particular, the use of role mining techniques for the discovery of roles from previously deployed authorizations has facilitated the configuration of such frameworks. However, the literature lacks from a clear basis for appraising and leveraging the learning outcomes of the role mining process. In this paper, we provide such a formal basis. We compare sets of roles by projecting roles from one set into the other set. This approach is useful to measure how comparable the two configurations of roles are, and to interpret each role. We formally define the problem of comparing sets of roles, and prove that the problem is NP-complete. Then, we propose an algorithm to map the inherent relationship between the sets based on Boolean expressions. We demonstrate the correctness and completeness of our solution, and investigate some further issues that may benefit from our approach, such as detection of unhandled perturbations or source misconfiguration. In particular, we emphasize that the presence of shadowed roles in the role configuration increases the time complexity of sets of roles comparison. We provide a definition of the shadowed roles problem and propose a solution that detects different cases of role shadowing.
In this work we describe a framework which allows to perform secure computations on non-integer values. To this end, we encode values in a way similar to floating point representation and describe protocols that allow to perform efficient secure two party computations on such encoded values. We present two approaches to realize the functionality of the framework. Both approaches come with different properties and are ready to use in various application scenarios. We implemented the framework in C++ and ran several experiments. This allows for a complexity analysis and for a comparison of the two different approaches. We further describe applications to privacy-preserving computations, which greatly benefit from the use of the new framework. In particular, we show how to run an important algorithm in the context of data analysis using Hidden Markov Models (HMM), namely the Viterbi algorithm, in a secure manner.
A continually increasing number of pictures and videos is shared in online social networks. Current sharing platforms, however, only offer limited options to define who has access to the content. Users may either share it with individuals or groups from their social graph, or make it available to the general public. Sharing content with users to which no social ties exist, even if they were physically close to the places where content was created and witnessed the same event, is however not supported by most existing platforms. We thus propose a novel approach to share content with such users based on so-called privacy bubbles. Privacy bubbles metaphorically represent the private sphere of the users and automatically confine the access to the content generated by the bubble creator to people within the bubble. Bubbles extend in both time and space, centered around the collection time and place, and their size can be adapted to the user's preferences. We confirm the user acceptance of our concept through a questionnaire-based study with 175 participants, and a prototype implementation shows the technical feasibility of our scheme.
Radio-frequency identification (RFID) tags have found their way into many applications. When tags implement cryptographic algorithms, side-channel analysis (SCA) attacks become a concern. Especially tags in the ultra-high frequency (UHF) range are susceptible to so-called parasitic-backscatter attacks that can be applied from a distance. Whereas it is known that such attacks are a threat for passive low-cost tags, no results are so far available for sensor-enabled tags. In this work, we evaluate the parasitic backscatter of wireless identification and sensing platform (WISP) tags by conducting differential electromagnetic analysis (DEMA) attacks. We apply the attacks on a passively as well as a semi-passively operated WISP tag from a distance of 30,cm and compare the results with an attack on a commercial low-cost tag. The results show that the evaluated WISP tags are less susceptible to DEMA attacks based on the parasitic backscatter than the evaluated commercial low-cost tag. Moreover, we present a measurement approach that allows to detect the weak parasitic backscatter modulated on the strong reader field without the need for an expensive hardware receiver or a dedicated demodulation circuit.
Whenever data is being processed, there are many places where parts of the data are temporarily stored; thus forensic analysis can reveal past activities, create a (partial) timeline and recover deleted data. While this fact is well known for computer forensics, multiple forensic tools exist to analyze data and the systematic analysis of database systems has only recently begun. This paper will describe the file format of the MySQL Database 5.1.32 with InnoDB Storage Engine. It will further explain with a practical example of how to reconstruct the data found in the file system of any SQL table. We will show how to reconstruct the table as it is, read data sets from the file and how to interpret the gained information.
Expressing security policies to govern distributed systems is a complex and error-prone task. Policies are hard to understand, often expressed with unfriendly syntax, making it difficult for security administrators and for business analysts to create intelligible specifications. We introduce the Hierarchical Policy Language for Distributed Systems (HiPoLDS), which has been designed to enable the specification of security policies in distributed systems in a concise, readable, and extensible way. HiPoLDS design focuses on decentralized execution environments under the control of multiple stakeholders. It represents policy enforcement through the use of distributed reference monitors, which control the flow of information between services. HiPoLDS allows the definition of both abstract and concrete policies, expressing respectively high-level properties required and concrete implementation details to be ultimately introduced into the service implementation.
We introduce Kynoid, a real-time monitoring and enforcement framework for Android. Kynoid is based on user-defined security policies which are defined for data-items. This allows users to define temporal, spatial, and destination constraints which have to hold for single items. We introduce an innovative approach to allow for the real-time tracking and enforcement of such policies. In this way, Kynoid is the first extension of Android which enables the sharing of resources while respecting individual security policies for the data-items stored in these resources. We outline Kynoid’s architecture, present its operation and discuss it in terms of applicability, performance, and usability. By providing a proof-of-concept implementation we further show the feasibility of our framework.
We show efficient, practical (server-aided) securetwo-party computation protocols ensuring privacy, correctnessand fairness in the presence of malicious (Byzantine) faults. Ourrequirements from the server are modest: to ensure privacyand correctness, we only assume offline set-up prior to protocolexecution; and to also ensure fairness, we further assume atrusted-decryption service, providing decryption service usingknown public key. The fairness-ensuring protocol is optimistic, i.e., the decryption service is invoked only in case of faults. Bothassumptions are feasible in practice and formally presented inthe hybrid model. The resulting protocols may be sufficientlyefficient, to allow deployment, in particular for financial appli-cations.
InnoDB is a powerful open-source storage engine for MySQL that gained much popularity during the recent years. This paper proposes methods for forensic analysis of InnoDB databases by analyzing the redo logs, primarily used for crash recovery within the storage engine. This new method can be very useful in forensic investigations where the attacker got admin privileges, or was the admin himself. While such a powerful attacker could cover tracks by manipulating the log files intended for fraud detection, data cannot be changed easily in the redo logs. Based on a prototype implementation, we show methods for recovering Insert, Delete and Update statements issued against a database.
A smart card is a tamper-resistant miniature computer that performs some basic computations on input a secret information. So far, smart cards have been widely used for securing many digital transactions (e.g., pay television, ATM machines).
Nowadays information systems play a vital role for organizations and individuals, which is why their protection is becoming increasingly important. Often, solutions are developed for very similar problems over and over again. An exchange of knowledge between experts would be desirable in order to prevent developing always the same solutions by independent persons. Such an exchange could also lead to solutions of higher quality, as existing approaches could be advanced, instead of always reinventing the security wheel. This paper examines how machine-readable information security knowledge can be shared between different organizations on the basis of a web portal utilizing Web-Protege. It can be shown that through the use of ontologies the domain of information security can be modeled and stored in a human and a machine-readable format, enabling both human editing and automation (e.g. for risk calculations). The evaluation of the web portal has shown that the most important challenge a tool for knowledge sharing has to face is the aspect of motivating users to participate in a knowledge exchange.
Mining approaches, such as role mining or organizational mining, can be applied to derive permissions and roles from a system's configuration or from log files. In this way, mining techniques document the current state of a system and produce current-state RBAC models. However, such current-state RBAC models most often follow from structures that have evolved over time and are not the result of a systematic rights management procedure. In contrast, role engineering is applied to define a tailored RBAC model for a particular organization or information system. Thus, role engineering techniques produce a target-state RBAC model that is customized for the business processes supported via the respective information system. The migration from a current-state RBAC model to a tailored target-state RBAC model is, however, a complex task. In this paper, we present a systematic approach to migrate current-state RBAC models to target-state RBAC models. In particular, we use model comparison techniques to identify differences between two RBAC models. Based on these differences, we derive migration rules that define which elements and element relations must be changed, added, or removed. A migration guide then includes all migration rules that need to be applied to a particular current-state RBAC model to produce the corresponding target-state RBAC model. In addition, we discuss different options for tool support and describe our implementation for the derivation of migration guides which is based on the Eclipse Modeling Framework (EMF).
The rising prevalence of Social Networking Sites (SNS) and their usage in multiple contexts poses new privacy challenges and increasingly prompts users to manage their online identity. To address privacy threats stemming from interacting with other users on SNS, effective Social Identity Management (SIdM) is a key requirement. It refers to the deliberate and targeted disclosure of personal attribute values to a subset of one's contacts or other users on the SNS. Protection against other entities such as the site operator itself or advertisers and application programmers is not covered by SIdM, but could be incorporated in further refinement steps. Features and settings to perform SIdM have been proposed and subsequently implemented partly by some SNS. Yet, these are often isolated solutions that lack integration into a reference framework that states the requirements for successfully managing one's identity. In this article, such a reference framework of existing and desired SIdM settings is derived from identity theory, literature analysis, and existing SNS. Based thereupon, we examine the SIdM capabilities of prevalent SNS and highlight possible improvements. Lastly, we reason about developing a metric to objectively compare the capability of SNS in regards to their support for SIdM.
The risk due to software vulnerabilities will not be completely resolved in the near future. Instead, putting reliable vulnerability measures into the hands of end-users so that informed decisions can be made regarding the relative security exposure incurred by choosing one software package over another is of importance. To that end, we propose two new security metrics, average active vulnerabilities (AAV) and vulnerability free days (VFD). These metrics capture both the speed with which new vulnerabilities are reported to vendors and the rate at which software vendors fix them. We then examine how the metrics are computed using currently available data sets and demonstrate their estimation in a simulation experiment using four different browsers as a case study. Finally, we discuss how the metrics may be used by the various stakeholders of software to aid usage decisions.
Information security has become a boardroom topic, lost laptops and hacked systems make front page news across the globe, but while technology is a key piece of any corporate security strategy, it is not enough. In this paper, Dr. Bunker examines the change in emphasis for information security from being hidden in the backroom of IT to a responsibility of every employee. Security needs to be taken into account in every IT activity, but it has to match the requirements and needs of the business. Information security has given way to the more comprehensive information assurance which can be categorized into more than thirty different strategic, operational and tactical controls. This paper examines the different controls and how a maturity model can be used to prioritise improvements by concentrating on the people and the processes as well as the technology. Finally it looks at the implications of cloud computing on information assurance and on how people can be an organizations greatest security asset.
