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Increasing the availability by using multiple cloud storage providers for replication comes at a price; not only does it increase storage costs with every replica, it also greatly disperses the information to different cloud storage systems. Thus, all storage locations must be trusted to not read that data. Contrary the cryptographic technique of secret sharing splits data into confidentiality protected shares and if the adversary does not have access to more than a pre-defined threshold k of those shares, then the data's confidentiality is protected. At the same time secret sharing also increases the availability because the legitimate user must only download the data from k out of n shares. The goal of this paper is to quantify the economic advantages of efficient and secure information dispersal strategies in multi-cloud settings based on the current market situation. Therefore, we put together a database of 63 cloud storage offers and analyzed opportunities to combine them into virtual storage services delivering availabilities of 99.999% at the best price. Additionally, the combined multi-cloud storage is leaning towards data protection legislation of the European Union (EU), as any combination of k shares includes at least one from an EU-based provider. This inhibits non-EU jurisdictions to 'subpoena' the required number of shares to reconstruct data without the help of an EU-based provider. Our findings show that it is possible to find combinations which give the cloud storage consumer the wanted high availability and legal compliance guarantee at half the cost of any two providers from within the EU storing unencrypted replicas.

Privacy requires more than just encryption of data before and during transmission. Privacy would actually demand hiding the sheer fact that communication takes place. This requires to protect meta-data from observation. We think that this feature is in particular useful and interesting for the Internet-of-Things. However, it requires strong cryptographic security mechanisms, like encryption of communication, to be in place. We motivate the need for strong privacy protection by highlighting privacy issues in a smart home use-case. We advance beyond encryption and discuss which existing techniques can be used to achieve unobservable communication. Then we describe the architecture needed to provide strong protection in this particular use-case. Lastly, we present the building blocks of the architecture we implemented so far on the Re-Mote sensor nodes running Contiki OS and sketch the computational and network overheads imposed by these techniques.

In this paper, we measure the overhead in message size and in firmware code-size for exchanging signed messages with constrained devices typically found in the Internet-of-Things (IoT) domain. The application of digital signatures on every important message in the IoT helps to increase its resilience against attacks and increases the data quality level. Other papers have shown that Elliptic Curve Cryptography (ECC) signatures can be applied on modern constrained devices. Our focus is on message size as we identified this to be the most prevailing problem as it relates to the storage required at each handling node and directly relates to the communication overhead, which in turn results in an increased energy consumption. We give analytical information for typical message sizes in two different protocols (MQTT and COAP), as well as real measurements on a Zolertia ReMOTE when it comes to firmware code-size overheads. Our measurements indicate that a suitable encoding of message level security can decrease the message overhead of signatures by at least 30 percent and still balance its usability by keeping it decodable into JSON, the prevailing exchange format of many IoT upper layer protocols. Our new HYBRID format is suitable to achieve end-to-end, i.e., device-to-application, integrity.

The Internet of Things (IoT) presents itself as a promising set of key technologies to provide advanced smart applications. IoT has become a major trend lately and smart solutions can be found in a large variety of products. Since it provides a flexible and easy way to gather data from huge numbers of devices and exploit them ot provide new applications, it has become a central research area lately. However, due to the fact that IoT aims to interconnect millions of constrained devices that are monitoring the everyday life of people, acting upon physical objects around them, the security and privacy challenges are huge. Nevertheless, only lately the research focus has been on security and privacy solutions. Many solutions and IoT frameworks have only a minimum set of security, which is a basic access control. The EU FP7 project RERUM has a main focus on designing an IoT architecture based on the concepts of Security and Privacy by design. A central part of RERUM is the implementation of a middleware layer that provides extra functionalities for improved security and privacy. This work, presents the main elements of the RERUM middleware, which is based on the widely accepted OpenIoT middleware.

The EC Horizon 2020 project PRISMACLOUD aims at cryptographically addressing several severe risks threatening end user security and privacy in current cloud settings. This shall be achieved by the provision of a reusable toolbox encapsulating cryptographic functionality from which dependably secure cloud services can be assembled. In order to provide a tangible abstraction of the complexity involved with the construction of cryptographically secured cloud services, we introduce the four-layer PRISMACLOUD architecture. Top down, it consists of a use cases (application) layer, a services layer, a tools layer, and a cryptographic primitives and protocols layer. In this paper we provide a detailed description of the P RISMACLOUD tools in terms of functional components, as well as how they interact to provide the desired security functionality. We also briefly describe the cutting-edge cryptographic primitives which are encompassed by the tools. Both the toolbox and the cryptographic primitives and protocols are being currently developed and will be provided as reference implementation by project end in July 2018.

The 4-eyes principle (4EP) is a well-known access control and authorization principle, and used in many scenarios to minimize the likelihood of corruption. It states that at least two separate entities must approve a message before it is considered authentic. Hence, an adversarial party aiming to forge bogus content is forced to convince other parties to collude in the attack. We present a formal framework along with a suitable security model. Namely, a party sets a policy for a given message which involves multiple additional approvers in order to authenticate the message. Finally, we show how these signatures are black-box realized by secure sanitizable signature schemes.

In this paper, we document the overhead in terms of runtime, firmware size, communication and energy consumption for Elliptic Curve Cryptography (ECC) signatures of modern ARM-based constrained devices. The experiments we have undertaken show that the cryptographic capabilities of the investigated Zolertia Re-Mote based on a TI's CC2538 chipset running Contiki OS is indeed suitable for the Internet-of-Things (IoT): Computing a signature using a curve with a 192-bit key length adds an additional runtime of roughly 200 ms. However, we found that in comparison to sending an unsigned message approximately two-thirds of the runtime overhead is spent on cryptographic operations, while sending the signed message accounts for the remainder. We give real measurements which can be used as a basis for analytical models. Our measurements show that the saving gained by using curves with lower security levels (i. e., 160-bit key length) is not worth the sacrifice in protection. While signatures add non-negligible overhead, we still think that the additional 200 ms (signing with secp192r) is worth consideration. This paper gives an indication of the true costs of cryptographically protected message integrity which is greater or equal to the cost of encryption. We show what needs to be spent in order to verify the origin of the data in the application, since in the IoT it will have travelled through many ‘things’.

We analyse accuracy, privacy, compressionratio and computational overhead of selected aggregation and perturbation methods in the Internet of Things (IoT). We measure over a real-life data set of detailed energy consumption logs of a single family household. We modelled privacy by simple, threshold-driven machine-learning algorithms that extract features of behaviour. The accuracy of those extraction is used as privacy metric. We state for different parameters of the aggregation, reduction and perturbation if the output still allows detections, as this follows the EU's data protection principle of “minimisation”: increased privacy due to less detailed data, but still good enough accuracy for the purpose. The result is that many detections for sensible predictions and intelligent reactions are still possible with lower quality data.

The Internet of Things (IoT) provides a platform for the interconnection of a plethora of smart objects. It has been widely accepted for providing Information and Communication Technologies (ICT) applications in many “smart” environments, such as cities, buildings, metering, and even agriculture. For several reasons though such applications have yet to achieve wide adoption; a major hurdle is the lack of user trust in the IoT and its role in everyday activities. RERUM, a recently started FP7 European Union project. aims to develop a framework which will allow IoT applications to consider security and privacy mechanisms early in their design phase, ensuring a configurable balance between reliability (requiring secure, trustworthy and precise data) and privacy (requiring data minimization for private information, like location). The RERUM framework will comprise an architecture, built upon novel network protocols and interfaces as well as the design of smart objects hardware. To highlight the challenges and evaluate the framework, RERUM will employ several Smart City application scenarios, which will be deployed and evaluated in real-world testbeds in two Smart Cities participating in the project. Here we detail the key technologies RERUM will investigate over the coming three years to reach its vision for IoT security, privacy and trust.

Smart Cities are considered recently as a promising solution for providing efficient services to citizens with the use of Information and Communication Technologies. With the latest advances on the Internet of Things, a new era has emerged in the Smart City domain, opening new opportunities for the development of efficient and low-cost applications that aim to improve the Quality of Life in cities. Although there is much research in this area, which has resulted in the development of many commercial products, significant parameters like reliability, security and privacy have not been considered as very important up until now. The newly launched FP7-SmartCities-2013 project RERUM aims to build upon the advances in the area of Internet of Things in Smart Cities and develop a framework to enhance reliability and security of smart city applications, with the citizen at the center of attention. This work presents four applications that will be developed within RERUM, gives a general description of the open reliability and security issues that have to be taken into account and gives an overall view of the solutions that RERUM will develop to address these issues.

Sanitizable signature schemes allow for altering signed data in a signer-controlled way by a semi-trusted third party. This is contrary to standard digital signature schemes, which do not permit any modifications by any party without invalidating the signature. Due to transparency, a strong privacy notion, outsiders cannot see if the signature for a message was created by the signer or by the semi-trusted party. Accountability allows the signer to prove to outsiders if a message was original or touched by the semi-trusted party. Currently, block-level accountability requires to drop transparency. We allow for accountability for sanitizable signatures with transparency on the block-level. Additionally, we generalize the concept of block-level properties to groups. This offers a even more fine-grained control and leads to more efficient schemes. We prove that group-level definitions imply both the block-level and message-level notions. We derive a provably secure construction, achieving our enhanced notions. A further modification of our construction achieves efficient group-level non-interactive public accountability. This construction only requires a constant amount of signature generations to achieve this property. Finally, we have implemented our constructions and the scheme introduced by Brzuska et al. at PKC '09 and provide a detailed performance analysis of our reference implementations.

Enforcing the right of access to personal data usually is a long-running process between a data subject and an organization that processes personal data. As of today, this task is commonly realized using a manual process based on postal communication or personal attendance and ends up conflicting with trade secret protection. In this paper, we present an automated architecture to enable exercising the right of access in the domain of inter-organizational business processes based on Web Services technology. Deriving its requirements from the legal, economical, and technical obligations, we show the architecture's overall approach solving the conflict between trade secret and exercising the right of access.

This paper describes ways for users to gain an insight into the actual communication flow of their Internet of Things (IoT) devices. The paper’s main objective is to enable a comparison of the flow with the devices’ intended purpose understandable to the device user. On the basis of what the device sends, the user should be enabled to decide whether the traffic is legitimate or not. With our framework no additional data will leave the user’s premises at any time. Only when a user decides that the traffic is unwanted communication flows the user can voluntarily transfer selected excerpts to a third party for further analysis. This limits data leakage compared to existing security incident event management (SIEM) solutions, where the monitoring third party seeks to constantly collect all information about the user’s traffic and thus constantly gets sensitive information. In this paper we propose a first set of tools for purely local analysis and user-friendly local visualizations. By this we educate the local user/operator of the IoT deployment and allow for more informed and more transparent decisions. Thus, we show that a privacy-preserving and thus more data-protection (GDPR) compliant monitoring of IoT-related network traffic is possible – and showcase how it will look.

Redact able signature schemes (RSS) allow removing blocks from signed data. State-of-the-art schemes have public redactions, i.e., Any party can remove parts from a signed message. This prohibits meaningful definitions of accountability. We address this gap by introducing the notion of accountable redact able signature schemes (ARSS). We present a generic construction which couples a sanitizable signature scheme (SSS) to profit from its accountability with an RSS to maintain the reduced malleability of RSSs. Depending on the building blocks, the resulting scheme offers transparency or public accountability. Transparency provides stronger privacy guarantees, while public accountability meets legal and application requirements.