With the daily increase in digitalization and integration of the physical and digital worlds, we need to better protect users’ privacy and identity. Attribute-based Credentials (ABCs) seem to be a promising technology for this task. In this paper, we provide comprehensive analyses of the readiness, maturity, and applicability of ABCs to real-world applications. Furthermore, we introduce our Privacy-Enhancing Authentication System (PEAS), which is based on ABCs and meets all privacy requirements such as anonymity and unlinkability of the user’s activities. Besides privacy features, PEAS also provides revocation mechanisms to identify and revoke malicious users. The system is suitable for deployment in real-world scenarios and runs on a wide range of user devices (e.g., smart cards, smartphones, and wearables).

Java Card stands out as a good choice for the development of smart card applications due to the high interoperability between different manufacturers, its security, and wide support of cryptographic algorithms. Despite extensive cryptographic support, current Java Cards do not support non-standard cryptographic algorithms such as post-quantum, secure-multiparty computations, and privacy-enhancing cryptographic schemes. Moreover, Java Card is restricted by the Application Programming Interface (API) in algebraic operations, which are the foundation of modern cryptographic schemes. This paper addresses the issue of developing these modern schemes by exploiting the limited cryptographic API provided by these types of cards. We show how to (ab)use the Java Card’s API to perform modular arithmetic operations, as well as basic operations on elliptic curves. Furthermore, we implement an attribute-based privacy-enhancing scheme on an off-the-shelf Java Card. To do so, we use our cryptographic API and several optimization techniques to make the scheme as efficient as possible. To demonstrate the practicality of our solution, we present the implementation results and benchmark tests.

In this article, we present two novel authenticated key agreement (AKA) schemes that are easily implementable and efficient even on constrained devices. Both schemes are constructed over elliptic curves and extend Schonorr’s signature of knowledge protocol. To the best of our knowledge, we introduce a first AKA protocol based on the proof of knowledge concept. This concept allows a client to prove its identity to a server via secret information while the server can learn nothing about the secret. Furthermore, we extend our protocol via secret sharing to support client multi-device authentication and multi-factor authentication features. In particular, the secret of the client can be distributed among the client’s devices.

Collaborative Indoor Positioning Systems have recently received considerable attention, mainly because they address some of the existing limitations of traditional Indoor Positioning System. In Collaborative Indoor Positioning Systems, Bluetooth Low Energy can be used to exchange positioning data and provide information (the Received Signal Strength Indicator) to establish the relative distance between the actors. The collaborative models exploit the position of actors and the relative position among them to allow positioning to external actors or improve the accuracy of the existing actors. However, the traditional protocols (e.g. iBeacon) are not yet ready for providing sufficient privacy protection. Therefore, this paper deals with privacy-enhancing technologies and their application in Collaborative Indoor Positioning System. In particular, we focus on cryptographic schemes which allow the verification of users without their identification, so-called Anonymous Attribute-Based Credentials schemes. As the main contribution, we present a cryptographic scheme that allows security and privacy-friendly sharing of location information sent through Bluetooth Low Energy advertising packets. In order to demonstrate the practicality of our scheme, we also present the results from our implementation and benchmarks on different devices.

Technology is continually undergoing a constituent development caused by the appearance of billions new interconnected “things” and their entrenchment in our daily lives. One of the underlying versatile technologies, namely wearables, is able to capture rich contextual information produced by such devices and use it to deliver a legitimately personalized experience. The main aim of this paper is to shed light on the history of wearable devices and provide a state-of-the-art review on the wearable market. Moreover, the paper provides an extensive and diverse classification of wearables, based on various factors, a discussion on wireless communication technologies, architectures, data processing aspects, and market status, as well as a variety of other actual information on wearable technology. Finally, the survey highlights the critical challenges and existing/future solutions.