We introduce context-aware scalable authentication (CASA) as a way of balancing security and usability for authentication. Our core idea is to choose an appropriate form of active authentication (e.g., typing a PIN) based on the combination of multiple passive factors (e.g., a user's current location) for authentication. We provide a probabilistic framework for dynamically selecting an active authentication scheme that satisfies a specified security requirement given passive factors. We also present the results of three user studies evaluating the feasibility and users' receptiveness of our concept. Our results suggest that location data has good potential as a passive factor, and that users can reduce up to 68% of active authentications when using an implementation of CASA, compared to always using fixed active authentication. Furthermore, our participants, including those who do not using any security mechanisms on their phones, were very positive about CASA and amenable to using it on their phones.

CASA: context-aware scalable authentication

In a context-aware service platform, service providers adapt their services to the current situation of the service users using context information retrieved from context information providers. In such a service provisioning platform, important trust and privacy issues arise, because different entities responsible for different tasks have to collaborate in the provisioning of the services. Context information is privacy sensitive by nature, making the communication and processing of this information a potential privacy threat. The main goal of this thesis is to learn how to support users and providers of context-aware services in managing the trade-off between privacy protection and context-based service adaptation. More and more precise context information retrieved from trustworthy context information providers allows context-aware service provider to adapt their services more reliably. However, more and more precise context information also means a higher risk for the service users in case of a privacy violation.

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Trust and privacy management support for context-aware service platforms

Mobile Android applications often have access to sensitive data and resources on the user device. Misuse of this data by malicious applications may result in privacy breaches and sensitive data leakage. An example would be a malicious application surreptitiously recording a confidential business conversation. The problem arises from the fact that Android users do not have control over the application capabilities once the applications have been granted the requested privileges upon installation. In many cases, however, whether an application may get a privilege depends on the specific user context and thus we need a context-based access control mechanism by which privileges can be dynamically granted or revoked to applications based on the specific context of the user. In this paper we propose such an access control mechanism. Our implementation of context differentiates between closely located sub-areas within the same location. We have modified the Android operating system so that context-based access control restrictions can be specified and enforced. We have performed several experiments to assess the efficiency of our access control mechanism and the accuracy of context detection.

Context-Based Access Control Systems for Mobile Devices

Context-based access control is an emerging approach for modeling adaptive solution, making access control management more flexible and powerful. But in the ubiquitous environment, this approach is not enough for many emerging security vulnerabilities. Thus, improving current access control mechanisms is still necessary. Risk is an effective tool used for decision-making in economics. In this paper, we design a new model for risk assessment in ubiquitous environment and use risk as a key component in decision-making process in our access control model. This solution makes access control management more dynamic and precise

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Enforcing Access Control Using Risk Assessment

There is a recent trend toward rule-based authorization systems to achieve flexible security policies. Also, new sensing technologies in pervasive computing make it possible to define context-sensitive rules, such as "allow database access only to staff who are currently located in the main office." However, these rules, or the facts that are needed to verify authority, often involve sensitive context information. This paper presents a secure context-sensitive authorization system that protects confidential information in facts or rules. Furthermore, our system allows multiple hosts in a distributed environment to perform the evaluation of an authorization query in a collaborative way; we do not need a universally trusted central host that maintains all the context information. The core of our approach is to decompose a proof for making an authorization decision into a set of subproofs produced on multiple different hosts, while preserving the integrity and confidentiality policies of the mutually untrusted principals operating these hosts

/pdf/secure-context-sensitive-authorization-bhl5p6f4te.pdf

Secure Context-Sensitive Authorization

We investigate the practical feasibility of using context information for controlling access to services. Based solely on situational context, we show that users can be transparently provided anonymous access to services and that service providers can still impose various security levels. Thereto, we propose context-sensitive verification methods that allow checking the user's claimed authenticity in various ways and to various degrees. More precisely, conventional information management approaches are used to compare historic contextual (service usage) data of an individual user or group. The result is a relatively strong, less intrusive and more flexible access control process that mimics our natural way of authentication and authorization in the physical world.

Context sensitive access control

We exploit the ability to sense and use context information to augment or replace the traditional static security measures by making them more adaptable to a given context and thereby less intrusive. We demonstrate that by fusing location information obtained from various sources that are associated to the user and are available over time, the confidence in the identity of the user can be increased considerably. In fact, the level of confidence in the identity of the user is related to the probability that the user is at a certain location. This probability is used as a measure to parameterize the authentication level of the user making it thereby much more adaptive to changing situational circumstances. In this paper we describe the theoretical background for a context-sensitive adaptation of authentication and the design and validation of the system that we have developed to adaptively authenticate a user on the basis of the location of his sensed identity tokens.

P. W. G. Ebben

Papers

Context sensitive access control

Context sensitive adaptive authentication