Detecting Key-Dependencies

The confidentiality of encrypted data depends on how well the key under which it was encrypted is maintained. If a session key was exchanged encrypted under a long-term key, exposure of the long-term key may reveal the session key and hence the data encrypted with it. The problem of key-dependencies between keys can be mapped onto connectivity of a graph, and the resulting graph can be inspected. This article presents a structured method (an algorithm) with which key-dependencies can be detected and analysed. Several well-known protocols are examined, and it is shown that they are vulnerable to certain attacks exploiting key-dependencies. Protocols which are free from this defect do exist. That is, when a session is terminated it is properly closed

A uniformity-based approach to location privacy

As location-based services emerge, many people feel exposed to high privacy threats. Privacy protection is a major challenge for such services and related applications. A simple approach is perturbation, which adds an artificial noise to positions and returns an obfuscated measurement to the requester. Our main finding is that, unless the noise is chosen properly, these methods do not withstand attacks based on statistical analysis. In this paper, we propose UniLO, an obfuscation operator which offers high assurances on obfuscation uniformity, even in case of imprecise location measurement. We also deal with service differentiation by proposing three UniLO-based obfuscation algorithms that offer multiple contemporaneous levels of privacy. Finally, we experimentally prove the superiority of the proposed algorithms compared to the state-of-the-art solutions, both in terms of utility and resistance against inference attacks

Key propagation in wireless sensor networks

With reference to a network consisting of sensor nodes connected by wireless links, we approach the problem of the distribution of the cryptographic keys. We present a solution based on communication channels connecting sequences of adjacent nodes. All the nodes in a channel share the same key. This result is obtained by propagating the key connecting the first two nodes to all the other nodes in the channel. The key propagation mechanism is also used for key replacement, as is required, for instance, in group communication to support forms of forward and backward secrecy, when a node leaves a group or a new node is added to an existing group

Protected pointers in wireless sensor networks

With reference to a distributed architecture consisting of sensor nodes connected by wireless links in an arbitrary network topology, we consider a segment-oriented implementation of the single address space paradigm of memory reference. In our approach, applications consist of active entities called components, which are distributed in the network nodes. A component accesses a given segment by presenting a handle for this segment. A handle is a form of pointer protected cryptographically. Handles allow an effective implementation of communications between components, and key replacement. The number of messages generated by the execution of the communication primitives is independent of the network size. The key replacement mechanism is well suited to reliable application rekeying over an unreliable network

Password systems: design and implementation

Critical infrastructures require protection systems that are both flexible and efficient. Flexibility is essential to capture the multi-organizational and state-based nature of these systems, efficiency is necessary to cope with limitations of hardware resources. To meet these requirements, we consider a classical protection environment featuring subjects that attempt to access the protected objects. We approach the problem of specifying the access privileges held by each subject. Our protection model associates a password system with each object; the password system features a password for each access privilege defined for this object. A subject can access the object if it holds a key matching one of the passwords in the password system, and the access privilege corresponding to this password permits to accomplish the access. Password systems are implemented as hierarchical bidimensional one-way chains. Trade-offs are possible between the memory requirements for storage of a password system and the processing time necessary to validate a key

Distributed storage protection in wireless sensor networks

With reference to a distributed architecture consisting of sensor nodes connected in a wireless network, we present a model of a protection system based on segments and applications. An application is the result of the joint activities of a set of cooperating nodes. A given node can access a segment stored in the primary memory of a different node only by presenting a gate for that segment. A gate is a form of pointer protected cryptographically, which references a segment and specifies a set of access rights for this segment. Gates can be freely transmitted between nodes, thereby granting the corresponding access permissions. Two special node functionalities are considered, segment servers and application servers. Segment servers are used for inter-application communication and information gathering. An application server is used in each application to support key management and rekeying. The rekey mechanism takes advantage of key naming to cope with losses of rekey messages. The total memory requirements for key and gate storage result to be a negligible fraction of the overall memory resources of the generic network node

Access Control for the Pepys Internet-Wide File-System

This paper describes the Access Control Model realized for the novel Pepys distributed, Internet-wide, file-system. The model design has been widely inspired to various existing standards and best practices about access control and security in file-system access, but it also echoes peculiar basic principles characterizing the design of Pepys, as well as the ΠP protocol, over which Pepys itself relies. The paper also provides technical details about how the model has been realized on a Linux port of Pepys

On Evaluating the Performance Impact of the IEEE 802.15.4 Security Sub-layer

Nowadays, wireless sensor networks (WSNs) are used in a wide range of application scenarios ranging from structural monitoring to health-care, from surveillance to industrial automation. Most of these applications require forms of secure communication. On the other hand, security has a cost in terms of reduced performance. In this paper we refer to the IEEE 802.15.4 standard and investigate the impact of the 802.15.4 security sub-layer on the WSN performance. Specifically, we analyze the impact that security mechanisms and options, as provided by the standard, have on the overall WSN performance, in terms of latency, goodput, and energy consumption. To this end, we develop an analytical model and a security enabled simulator. We also use a real testbed, based on a complete open-source implementation of the standard, to validate simulation and analytical results, as well as to better understand the limits of the current WSN technology

ABE-Cities: An attribute-based encryption system for smart cities

In the near future, a technological revolution will involve our cities, where a variety of smart services based on the Internet of Things will be developed to facilitate the needs of the citizens. Sensing devices are already being deployed in urban environments, and they will generate huge amounts of data. Such data are typically outsourced to some cloud storage because this lowers capital and operating expenses and guarantees high availability. However, cloud storage may have incentives to release stored data to unauthorized entities. In this work we present ABE-Cities, an encryption scheme for urban sensing which solves the above problems while ensuring fine-grained access control on data by means of Attribute-Based Encryption (ABE). Basically, ABE-Cities encrypts data before storing it in the cloud and provides users with keys able to decrypt only those portions of data the user is authorized to access. In ABE-Cities, the sensing devices perform only lightweight symmetric cryptography operations, thus they can also be resource-constrained. ABE-Cities provides planned expiration of keys, as well as their unplanned revocation. We propose methods to make the key revocation efficient, and we show by simulations the overall efficiency of ABE-Cities