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Universal Serial Bus (USB) Flash Drives are nowadays one of the most convenient and diffused means to transfer files, especially when no Internet connection is available. However, USB flash drives are also one of the most common attack vectors used to gain unauthorized access to host devices. For instance, it is possible to replace a USB drive so that when the USB key is connected, it would install passwords stealing tools, root-kit software, and other disrupting malware. In such a way, an attacker can steal sensitive information via the USB-connected devices, as well as inject any kind of malicious software into the host. To thwart the above-cited raising threats, we propose MAGNETO, an efficient, non-interactive, and privacy-preserving framework to verify the authenticity of a USB flash drive, rooted in the analysis of its unintentional magnetic emissions. We show that the magnetic emissions radiated during boot operations on a specific host are unique for each device, and sufficient to uniquely fingerprint both the brand and the model of the USB flash drive, or the specific USB device, depending on the used equipment. Our investigation on 59 different USB flash drives---belonging to 17 brands, including the top brands purchased on Amazon in mid-2019---, reveals a minimum classification accuracy of 98.2% in the identification of both brand and model, accompanied by a negligible time and computational overhead. MAGNETO can also identify the specific USB Flash drive, with a minimum classification accuracy of 91.2%. Overall, MAGNETO proves that unintentional magnetic emissions can be considered as a viable and reliable means to fingerprint read-only USB flash drives. Finally, future research directions in this domain are also discussed., Accepted for publication in ACM Transactions on Embedded Computing Systems (TECS) in September 2020

We present a new machine learning-based attack that exploits network patterns to detect the presence of smart IoT devices and running services in the WiFi radio spectrum. We perform an extensive measurement campaign of data collection, and we build up a model describing the traffic patterns characterizing three popular IoT smart home devices, i.e., Google Nest Mini, Amazon Echo, and Amazon Echo Dot. We prove that it is possible to detect and identify with overwhelming probability their presence and the services running by the aforementioned devices in a crowded WiFi scenario. This work proves that standard encryption techniques alone are not sufficient to protect the privacy of the end-user, since the network traffic itself exposes the presence of both the device and the associated service. While more work is required to prevent non-trusted third parties to detect and identify the user’s devices, we introduce Eclipse, a technique to mitigate these types of attacks, which reshapes the traffic making the identification of the devices and the associated services similar to the random classification baseline.

The massive deployment of IoT devices being utilized by home automation, industrial and military scenarios demands for high security and privacy standards to be achieved through innovative solutions. This paper proposes KaFHCa, a crypto-less protocol that generates shared secret keys by combining random frequency hopping collisions and source indistinguishability independently of the radio channel status. While other solutions tie the secret bit rate generation to the current radio channel conditions, thus becoming unpractical in static environments, KaFHCa guarantees almost the same secret bitrate independently of the channel conditions. KaFHCa generates shared secrets through random collisions of the transmitter and the receiver in the radio spectrum, and leverages on the fading phenomena to achieve source indistinguishability, thus preventing unauthorized eavesdroppers from inferring the key. The proposed solution is (almost) independent of the adversary position, works under the conservative assumption of channel fading ({\sigma} = 8dB), and is capable of generating a secret key of 128 bits with less than 564 transmissions.

Wireless devices resorting to event-triggered communications have been proved to suffer critical privacy issues, due to the intrinsic leakage associated with radio-frequency (RF) emissions. In this paper, we move the attack frontier forward by proposing BrokenStrokes: an inexpensive, easy to implement, efficient, and effective attack able to detect the typing of a pre-defined keyword by only eavesdropping the communication channel used by the wireless keyboard. BrokenStrokes proves itself to be a particularly dreadful attack: it achieves its goal when the eavesdropping antenna is up to 15 meters from the target keyboard, regardless of the encryption scheme, the communication protocol, the presence of radio noise, and the presence of physical obstacles. While we detail the attack in three current scenarios and discuss its striking performance---its success probability exceeds 90%6 in normal operating conditions---, we also provide some suggestions on how to mitigate it. The data utilized in this paper have been released as open-source to allow practitioners, industries, and academia to verify our claims and use them as a basis for further developments.

Establishing confidentiality between communicating peers is still an issue in contexts where solutions based on asymmetric keys are not viable, such as in dynamic Internet of Things (IoT) systems made up of heterogeneous and resource constrained devices. From the current literature, channel anonymity emerges as a promising methodology able to support key-establishment protocols. But, to the best of authors’ knowledge, no works already demonstrated its practical adoption over a concrete communication technology. To bridge this gap, we experimentally show that a lightweight key-establishment protocol based on channel anonymity is viable. The contributions of this work are mainfold. First, we introduce EXCHANge, a protocol that achieves key-establishment exploiting channel anonymity despite the presence of either a passive or active global-eavesdropper adversary. Second, we evaluate the performance of EXCHANge through an extensive experimental campaign involving real world IoT devices (OpenMote-CC2538). Our results demonstrate that the proposed solution introduces a limited overhead, thus being able to meet the requirements of resource constrained devices Finally, we experimentally demonstrate the security of the EXCHANge protocol against passive and active adversaries. Overall, this paper proves that channel anonymity can be a powerful tool in the IoT setting, to achieve a secure, effective, and efficient key-establishment.

We propose GopJam, a solution to thwart jamming from a network perspective. GopJam combines a keyless approach with a gossip-based diffusion of the information to be broadcast. To the best of our knowledge, we are the first ones to leverage these two features at the same time. Our contributions are manifold: first, we provide a theoretical model for the message propagation speed and the associated broadcast delay. Later, we test GopJam against two adversarial models: a standard one where the jammer—as widely accepted in the literature—, jams a fraction of the radio spectrum; and, a smart one where the jammer exploits a combination of the eavesdropping and jamming functionalities in order to improve its chances to disrupt the propagation of the message. Among the several features enjoyed by GopJam, it is worth noticing that, being keyless, it does not require any pre-shared secret to evade the action of the jammer; therefore, it is particularly suitable for scenarios characterized by a moderate to high network node volatility. Further, GopJam is particularly effective also in benign scenarios (no jamming): our protocol enjoys the characteristics of gossiping protocols, guaranteeing a short delay in network message propagation. For instance, with a fraction of the jammed spectrum equal to δJ = 0.9, and the smart adversary configuration, the protocol requires just about 1000 time slots to deliver the message to the 100% of the nodes (512). Finally, extensive simulations prove the effectiveness of our protocol in delivering the message to all the network nodes in each of the considered scenarios (benign scenario, standard jammer, and the newly introduced smart jammer). This work, other than being relevant on its own, also paves the way to further research in the brand new area of gossip-based counter-jamming techniques.

This paper presents a thorough analysis of Freedom of Speech (FoS): a lightweight, fully distributed, and probabilistic protocol that assures the delivery of a message to be broadcast notwithstanding the presence of a jammer. FoS enjoys several features when compared to competing schemes: (i) it requires each node to store only N symmetric pairwise keys; (ii) node joining and node eviction require just minimal intervention on the already operating nodes; and, finally, (iii) it is overall highly efficient in terms of required computation and message exchange. We provide a detailed theoretical analysis of our solution supported by extensive simulations considering different operating scenarios: we start from a simplified network assumption of one only transmitter that wants to broadcast a message and we subsequently move to a realistic scenario where nodes that have received the message act themselves as a proxy. We propose a theoretical framework to model the protocol performance starting by a benign scenario (no jamming activities). Later, we extend the model to more hostile environments considering firstly a jammer with no knowledge of the nodes' secret keys (external jammer) and subsequently, a jammer aware of a fraction of the nodes' secret keys (internal jammer). The experimental results do confirm our theoretical analysis and show the overall viability of our solution. In particular, FoS outperforms competitor solutions for deployment scenarios characterized by even a moderated degree of node volatility. Scopus

The Global Positioning System (GPS) has been proved to be exposed to several cybersecurity attacks, due to its intrinsic insecure design. GPS spoofing is one of the most easiest, cheap, and dreadful attacks that can be delivered: fake GPS signals can be sent to a target device and make it moving according to a pre-computed path. Although some proposals exist to discriminate between legitimate and rogue GPS signals, those solutions are still difficult to deploy, since they resort to special hardware capable of identifying physical properties of original GPS signals. In this paper, we propose a brand new approach, exploiting the broadcast signals transmitted by the mobile cellular network infrastructure to validate the position received by the GPS infrastructure. In detail, we provide several contributions: (i) the architecture of our solution; (ii) the analytic models related to the GSM infrastructure, including the number of in-range base stations, the distance to the base stations, and the received signal strength; and, (iii) the results achieved via an extensive measurement campaign, carried out by first collecting GPS signals while driving for more than 158 Km, and then using these data to build an experimental model for the evaluation of the performance of our technique in the detection of a wide number of emulated spoofing attacks. Finally, we also tested our solution against a real GPS spoofing attack. We proved it being able to guarantee 0% false positive and 100% detection with an almost negligible delay---all the system parameters being finely tunable, allowing for a wide range of possible trade-offs.

We propose a methodology to detect the current status of a powered-on drone (flying or at rest), leveraging just the communication traffic exchanged between the drone and its Remote Controller (RC). Our solution, other than being the first of its kind, does not require either any special hardware or to transmit any signal; it is built applying standard classification algorithms to the eavesdropped traffic, analyzing features such as packets inter-arrival time and size. Moreover, it is fully passive and it resorts to cheap and general purpose hardware. To evaluate the effectiveness of our solution, we collected real communication measurements from a drone running the widespread ArduCopter open-source firmware, mounted onboard on a wide range of commercial amateur drones. The results prove that our methodology can efficiently and effectively identify the current state of a powered-on drone, i.e., if it is flying or lying on the ground. In addition, we estimate a lower bound on the time required to identify the status of a drone with the requested level of assurance. The quality and viability of our solution do prove that network traffic analysis can be successfully adopted for drone status identification, and pave the way for future research in the area.

Comunicació presentada a: IEEE Conference on Communications and Network Security (CNS), celebrada a Pequín (Xina) del 30 d'octubre a l'1 de Juny de 2018. In this paper we propose N-Guard: a portable, effective, and efficient solution to thwart contactless skimming of NFC cards. Our solution enables an NFC-compliant smartphone to protect the user's cards, preventing the adversary from harvesting the cards' data. Moreover, we also introduce a fine grained access control mechanism, allowing the user to discriminate between NFC cards that can be opportunistically queried and sensitive ones that can be read only under the strict permission of the owner. We implemented a proof-of-concept of N-Guard for Android OS and tested it under several digital skimming scenarios showing its effectiveness in thwarting unauthorized access attempts. Moreover, we also measured the consumption of N-Guard and proved that its energy consumption is negligible. Further, it is worth noting that N-Guard requires neither any specific modification to the NFC standard, nor any change on users behavior. Finally, through some empirical evidence, we show N-Guard to be effective even when the interaction between the NFC tags and the reader is driven by proprietary protocols (e.g. Mastercard). All the reported results, having being developed over an NFC-enabled credit-card use case, are general and applicable to all NFC tags.

We introduce Shooting to the Stars, in short SttS, a secure location verification algorithm leveraging Meteor Burst Communications (MBC)–the ephemeral, ionized stripe generated by meteors. SttS leverages intrinsic peculiarities of MBC, such as robustness to both eavesdropping and jamming, while also enjoying ease of deployment and secure authentication of the transmitting source. SttS enables the verification of the position of a passive receiver by exploiting the radio reflection properties of ephemeral meteor trails, combined with multiple anchors (N) that can be deployed even hundreds of Km from the receiver itself. We developed a complete theoretical model for our solution–rooted on sound literature and past experimental campaigns–, and fully tested it with extensive simulations. Results show that SttS is highly reliable in guaranteeing position verification, and that it can detect a location spoofing attack even when up to $\left({\lceil \frac {N}{2}\rceil -1}\right)$ anchors are compromised by an adversary. Finally, it is completely tunable, trading off accuracy with the number of observed trails–for instance, observing just 200 trails enables to correctly classify the the location as valid or not with a 0.99 probability.

This work presents an effective and efficient solution (SLiFi) to the evil twin attack in wireless networks. The evil twin is a rogue Wifi Access Point (AP) that pretends to be an authentic one by using the same network configuration, including the (i) Service Set Identifier (SSID), (ii) the communication channel, and finally (iii) the MAC address of the purported AP. The evil twin is a trap set-up by an adversary willing to eavesdrop on the user's Internet traffic. The attack is relatively easy to implement, hard to detect and it can have a severe impact on a user's privacy. Many researchers focused on this attack and provided defences from different perspectives: network, access point and client side. Unfortunately, all the solutions provided so far are still not ready for mass deployment since they involve significant modifications to the 802.11 WiFi protocol. In the following, we report some of the most important ones. Gonzales et al. [1] proposed to construct a context vector containing the order of all APs detected at a particular time, with their SSID and RSSI values. This enables the client to compare its future associations with the stored context vector. Bauer et al. [2] proposed SWAT which is a request-response protocol. This approach provides a one-way AP authentication and allows the client to establish a connection to the network through a shared secret key to create a secure session based on the principle of trust-on-first-use (TOFU). Lanze et al. [3] introduced a new technique using the aircrack-ng suite. The tool airbase-ng is set up on all the devices and the beacon frames are collected from various APs. The proposed approach compares the Timing Synchronization Function (TSF) timestamps and their corresponding receiving times in order to spot anomalies due to message proxying and therefore, the presence of a malicious AP. Finally, Gangasagare et al. [4] propose a fingerprinting technique based on network traffic enabling to detect if the AP relays the traffic through another wireless connection. SLiFi does not require any changes to the already existing communication protocols and it enables the access point authentication (by the users) in a fast and reliable way. Indeed, SLiFi enables the user to authenticate the legitimate AP by exploiting a Visible Light Communication (VLC) channel. SLiFi involves two parties, i.e., the (honest) AP provided with a Wi-Fi interface and able to transmit data through a VLC channel, and an end-user, provided with a software that enables data to be read from a VLC channel, e.g., by using a webcam. SLiFi exploits four phases: AP's Public Key (PubKey) broadcast. The AP transmits its own PubKey to the end-user via an authenticated channel (VLC). The PubKey broadcast process is completely transparent to the user since each bit of the PubKey is delivered by quickly switching on and off the light of the room in which the user is. This is achieved by standard techniques of VLC: the human eye cannot perceive the fast blinking light but other devices, such as special webcams, can detect the brightness change. Subsequently, the brightness changes can be translated to a sequence of bit values. Seed generation. The end-user retrieves the public key from the VLC channel by using a webcam and transmits back to the AP a randomly generated seed encrypted with the AP's public key. The PubKey is securely delivered to the user since any other non-authorized light source can be easily spotted. Therefore, only one authorized VLC transmitter will be in place and it will deliver the PubKey of the AP. The client can now use the trusted PubKey to send back to the AP an encrypted seed to be used for the key generation. Secret key generation. The AP receives the user's encrypted seed via the Wi-Fi channel, decrypts the seed using its private key, and sends an acknowledgment message encrypted with the seed back to the end-user. This phase performs the key-agreement and both the AP and the user's device converge to a shared secret key. Encrypted communication. Any further communications between the end-user and the AP will be encrypted with the shared secret key, i.e., the seed generated by the client. SLiFi is compliant with multiple clients, indeed the AP can easily deal with concurrent communications. Moreover, from a practical perspective, SLiFi can be adopted to only generate the shared secret key and passing it to the already existing encryption algorithm, e.g., WPA2 or WPA2-Enterprise. To evaluate SliFi, we built a proof-of-concept using a (1) Raspberry Pi which emulates the AP, a (2) set of LEDs to transmit the PubKey, and (3) standard laptops to act as clients with webcams. All the software components have been implemented and tested. We performed several tests to evaluate the feasibility of our solution. To test reliability of VLC transmission, we ran various experiments to measure the Public key transmission errors as a function of the VLC bit-rate, and we observed that PubKey can reliability transmitted within a reasonable time frame. Finally, our results prove the feasibility of the solution in terms of time to establish the key and robustness to the evil-twin attack. References 1. H. Gonzales, K. Bauer, J. Lindqvist, D. McCoy, and D. Sicker. Practical Defenses for Evil Twin Attacks in 802.11. In IEEE Globecom Communications and Information Security Symposium (Globecom 2010), Miami, FL, December 2010. 2. K. Bauer, H. Gonzales, and D. McCoy. Mitigating Evil Twin Attacks in 802.11. January 2009. 3. F. Lanze, A. Panchenko, T. Engel, and I. Alcaide. Undesired Relatives: Protection Mechanisms against the Evil Twin Attack in IEEE 802.11. 4. M. Gangasagare. Active User-Side Evil Twin Access Point Detection. International Journal of Scientific & Engineering Research, May 2014.

Server-side authenticated key-establishment protocols are characterized by placing a heavy workload on the server. We propose LAKE: a new protocol that enables amortizing servers’ workload peaks by moving most of the computational burden to the clients. We provide a formal analysis of the LAKE protocol under the Canetti-Krawczyk model and prove it to be secure. To the best of our knowledge, this is the most computationally efficient authenticated key-establishment ever proposed in the literature.

Wireless Sensor Networks (WSNs) are susceptible to a wide range of attacks due to their distributed nature, limited sensor resources, and lack of tamper resistance. Once a sensor is corrupted, the adversary learns all secrets. Thereafter, most security measures become ineffective. Recovering secrecy after compromise requires either help from a trusted third party or access to a source of high-quality cryptographic randomness. Neither is available in Unattended Wireless Sensor Networks (UWSNs), where the sink visits the network periodically. Prior results have shown that sensor collaboration is an effective but expensive means of obtaining probabilistic intrusion resilience in static UWSNs. In this paper, we focus on intrusion resilience in Mobile Unattended Wireless Sensor Networks (μUWSNs), where sensors move according to some mobility models. Note that such a mobility feature could be independent from security (e.g., sensors move to improve area coverage). We define novel security metrics to evaluate intrusion resilience protocols for sensor networks. We also propose a cooperative protocol that - by leveraging sensor mobility - allows compromised sensors to recover secure state after compromise. This is obtained with very low overhead and in a fully distributed fashion. Thorough analysis and extensive simulations support our findings.

Cognitive Radio Networks (CRNs) are recognized as the enabling technology for improving future bandwidth utilization. CRNs have intrinsic security threats due to their opportunistic exploitation of the bandwidth. In particular, jamming is one of the most challenging security threats for CRNs. In this work we provide several contributions about jamming in CRNs: we classify the various jamming strategies, provide a review of recent anti-jamming countermeasures, and introduce a novel anti-jamming solution for CRNs. Our solution is based on a distributed, probabilistic protocol that, while on the one hand could introduce some (limited) delay in message propagation, on the other hand enjoys several features: it avoids control channels for the coordination of the secondary users; does not need any information related to the node neighborhood; and it does not leverage any knowledge or statistics about the channel usage. Given the novelty of the proposal and its potential to thwart jamming in CRNs, we believe it could pave the way for further research in the field.

In this paper, we present a novel probabilistic protocol (COKE) to allow two wireless communicating parties to commit over-the-air (OTA) on a shared secret, even in the presence of a globally eavesdropping adversary. The proposed solution leverages no crypto but just plaintext messages exchange. Indeed, the security of the solution relies on the difficulty for the adversary to correctly identify, for each one-bit transmission, the sender of that bit-not its value, which is indeed exchanged in cleartext. Due to the low requirements of COKE (essentially, the capability to send a few wireless messages), it is particularly suited for resource constrained wireless devices (e.g., WNSs, wireless embedded systems), as well as for those scenarios where just energy saving is at premium, such as smartphones.

This paper is not a survey related to generic wireless sensor networks (WSNs), which have been largely treated in a number of survey papers addressing more focused issues; rather, it specifically addresses architectural aspects related to WSNs in some way connected with a satellite link, a topic that presents challenging interworking aspects. The main objective is to provide an overview of the potential role of a satellite segment in future WSNs. In this perspective, requirements of the most meaningful WSN applications have been drawn and matched to characteristics of various satellite/space systems in order to identify suitable integrated configurations. Copyright © 2012 John Wiley & Sons, Ltd.

We propose Strength of Crowd (SoC), a distributed Internet of Things (IoT) protocol that guarantees message broadcast from an initiator to all network nodes in the presence of either a reactive or a proactive jammer, that targets a variable portion of the radio spectrum. SoC exploits a simple, yet innovative and effective idea: nodes not (currently) involved in the broadcast process transmit decoy messages that cannot be distinguished (by the jammer) from the real ones. Therefore, the jammer has to implement a best-effort strategy to jam all the concurrent communications up to its frequency/energy budget. SoC exploits the inherent parallelism that stems from the massive deployments of IoT nodes to guarantee a high number of concurrent communications, exhausting the jammer capabilities and hence leaving a subset of the communications not jammed. It is worth noting that SoC could be adopted in several wireless scenarios, however, we focus on its application to the Wireless Sensor Networks (WSN) domain, including IoT, Machine-to-Machine (M2M), Device-to-Device (D2D), to name a few. In this framework, we provide several contributions: firstly, we show the details of the SoC protocol, as well as its integration with the IEEE 802.15.4-2015 MAC protocol, secondly, we study the broadcast delay to deliver the message to all the nodes in the network, and finally, we run an extensive simulation and experimental campaign to test our solution. We consider the state-of-the-art OpenMote-B experimental platform, adopting the OpenWSN open-source protocol stack. Experimental results confirm the quality and viability of our solution.

One of the aims of the SatNEx (Satellite Network of Excellence, http://www.satnex.de) European project is to provide the scientific community that operates on satellite communications with measurement campaign results and evaluation tools, in order to support research activities that investigate problems in satellite communications at different levels of the OSI stack. In fact, the research activities developed in SatNEx address the most relevant aspects of satellite communications, such as channel modulation and coding schemes, access strategies, advanced networking, end-to-end quality of service, transport performance, delay tolerant networks, and new applications. Even if SatNEx is mainly devoted to satellite communications, integration of satellite and terrestrial wireless segments has also been taken into account. This paper presents the results obtained in the specific research activity devoted to trials and testbeds developed during the SatNEx project. The high number of authors of this paper is an indication of the strong collaborative work sustained, the numerous measurement campaigns, and the complexity in developing integrated testbeds. Copyright © 2008 John Wiley & Sons, Ltd.

In this paper, we introduce a lightweight, fully distributed, and probabilistic protocol---Freedom of Speech (FoS)---that assures the delivery of a message to be broadcast (to N nodes) notwithstanding the presence of a powerful jammer. FoS enjoys several features when compared to competing schemes: it requires each node to store just N symmetric pairwise keys; node joining and node eviction require just minimal intervention on the already operating nodes; and, it is highly efficient in terms of required computation and message exchange.We provide a thorough analysis on the number of communications required by FoS to broadcast a message. We show that FoS is comparable to the state of the art solution under a realistic scenario, while it enjoys unique properties such as an optimal network reconfiguration and low overhead as for both computation and storage Extensive simulations support our findings.

Wireless Sensor Networks (WSNs) are susceptible to a wide range of attacks due to their distributed nature, limited sensor resources and lack of tamper-resistance. Once a sensor is corrupted, the adversary learns all secrets and (even if the sensor is later released) it is very difficult for the sensor to regain security, i.e., to obtain intrusion-resilience. Existing solutions rely on the presence of an on-line trusted third party, such as a sink, or on the availability of secure hardware on sensors. Neither assumption is realistic in large-scale Unattended WSNs (UWSNs), characterized by long periods of disconnected operation and periodic visits by the sink. In such settings, a mobile adversary can gradually corrupt the entire network during the intervals between sink visits. As shown in some recent work, intrusionresilience in UWSNs can be attained (to a degree) via cooperative self-healing techniques. In this paper, we focus on intrusion-resilience in Mobile Unattended Wireless Sensor Networks ( UWSNs) where sensors move according to some mobility model. We argue that sensor mobility motivates a specific type of adversary and defending against it requires new security techniques. Concretely, we propose a cooperative protocol that - by leveraging sensor mobility - allows compromised sensors to recover secure state after compromise. This is obtained with very low overhead and in a fully distributed fashion. We provide a thorough analysis of the proposed protocol and support it by extensive simulation results.

In this paper we present ESC: an efficient, scalable, and crypto-less solution for the establishment of a secure wireless network (that is, a network where, for any pair of nodes, there exists a path composed of encrypted links). ESC guarantees the security of the 90% of the network scenario in the presence of 4 global eavesdropper adversaries with about 370 local peer-to-peer communications avoiding both pre-shared secrets and cryptographic functions. The founding block of our proposal is inspired by COKE [1], where the bits of the secret key associated to a link are generated via a multi-round protocol that, at each round, leverages just channel anonymity. Starting from this founding block, we further provide several relevant contributions: we devise a theoretical model and prove a lower bound for the probability to establish a safe-link in the presence of a global eavesdropper adversary. Further, we study the emergent property of network security achieved via the local property of safe-link establishment. To characterize this feature, we introduce two intuitive and useful metrics: network safety and largest safe component , both aimed at capturing the security features provided by ESC. The thorough theoretical analysis of our proposal, the security proof (under the Canetti–Krawczyk model) supporting our key establishment protocol, as well as our extensive simulations showing the effectiveness and efficiency of our protocol for a wide range of network configuration parameters, make our proposal a viable solution to enforce the security of real networks, other than paving the way for further research in this field.

Encrypted communication in wireless sensor networks oftentimes requires additional randomness and frequent re-keying in order to avoid known-plain text attacks. Conventional approaches for shared secret generation suffer however from various disadvantages, such as necessity of a trusted third party, protocol scalability, and especially, the computational resources needed for performance-demanding public-key protocols. To appropriately respond to the increasing disproportions between a computationally powerful adversary and lightweight wireless devices, a cyber-physical approach has recently attracted much attention. The general idea is to leverage the properties of the physical world and include them in a design of lightweight security protocols. Especially valuable physical property is the erratic and unpredictable nature of multi-path signal propagation which has already shown itself as a rich source of randomness. This work presents a new cyber-physical approach in order to make secure wireless sensor communications and proposes a secret key extraction algorithm that leverages signal strength fluctuations resulting from dynamic physical environments, e.g. environments experiencing human movements. In particular, this work presents a systematic experimental evaluation by using a real-world sensor network, and analyzes the impact of different moving patterns on legitimate devices and an eavesdropper. Finally, this work quantifies the main factors that influence the key establishment algorithm and propose a protocol which allows secret sharing in an effective and efficient way.

Pairwise secret key establishment leveraging properties of the wireless channel, is an effective security means in scenarios where no common secret or PKI is available. Related work has shown that secret bit streams can be extracted from, e.g., signal strength ratio measurement between two peers. However, they all require a considerable amount of computing resources by the two parties. In this paper we present SHAKE, a novel algorithm to establish a key using the physical properties of the wireless channel. SHAKE is particularly suitable for scenarios where the two peers have very diverse computational resources. For example, SHAKE can be used to establish a key between a sensor and the sink in a Wireless Sensor Network. We show that a secret key can be established shifting the computational burden on one peer while the other party only require one hash evaluation, what can be afforded by any resource constrained device. We evaluate SHAKE through theoretical analysis and provide validation through real world measurements. According to our experiments, the proposed protocol generates high-entropy bit at remarkable rates and enjoys minimal computational complexity requirements at one of the two parties.

Multicast video streaming in heterogeneous networks undergoes to very different physical constraints, in fact, such networks are characterized by different QoS parameters, involving one or more transcoding process between the sender and the receivers. Video streaming authentication algorithms must be robust to transcoding processes and must guarantee the copyright of the video owner/producer. We propose a real-time video streaming authentication algorithm that can guarantee the copyright of the video owner and that we prove to be robust to packet loss and transcoding processes.

We present a novel video stream authentication scheme which combines signature amortization by means of hash chains and an advanced watermarking technique. We propose a new hash chain construction, the Duplex Hash Chain, which allows us to achieve bit-by-bit authentication that is robust to low bit error rates. This construction is well suited for wireless broadcast communications characterized by low packet losses such as in satellite networks. Moreover, neither hardware upgrades nor specific end-user equipment are needed to enjoy the authentication services. The computation overhead experienced on the receiver only sums to two hashes per block of pictures and one digital signature verification for the whole received stream. This overhead introduces a provably negligible decrease in video quality. A thorough analysis of the proposed solution is provided in conjunction with extensive simulations.

Quality of experience is becoming an important parameter for estimating the end user perceived video quality. Video coding algorithms are currently increasing the compression performances by exploiting the temporal and spatial correlations of multimedia information. Such a trend is self-defeating in hybrid networks, due to the frequent channel impairments experienced. Here, the authors present a double-stage forward error correction (FEC) scheme to reduce the channel impairments that a multimedia communication undergoes when broadcasting a video stream through an hybrid infrastructure constituted by satellite and terrestrial wireless links. The authors present a detailed statistical description of the terrestrial wireless channel and exploit it to design the parameters for tuning the algorithm. Simulations results show that this approach not only performs better than the error recovery techniques currently used in the literature, but it also experiences a significant reduction in the bandwidth overhead.

Following the vision of Ambient Intelligence (AmI), this paper introduces and evaluates a novel security scheme that takes the advantage of the unpredictable and erratic behavior of wireless communication to generate secret keys. The main advantage is that the secret key generation is applicable to every wireless device, independently of their hardware characteristics as it only requires a wireless interface and a human movement, which inherently affects the signal propagation within the physical environment. To analyze the applicability of this scheme, we implement and systematically evaluate the key generation using a wireless sensor network deployed in a real-world scenario. The analysis clarifies how different factors influence the amount of randomness collected from the physical environment, and it also shows that guessing attacks from an eavesdropper are negligible even if it is able to eavesdrop the complete wireless communication.

One important factor complicating security in Wireless Sensor Networks (WSNs) is lack of inexpensive tamper-resistant hardware in commodity sensors. Once an adversary compromises a sensor, all memory and forms of storage become exposed, along with all secrets. Thereafter, any cryptographic remedy ceases to be effective. Regaining sensor security after compromise (i.e., intrusion-resilience) is a formidable challenge. Prior approaches rely on either (1) the presence of an on-line trusted third party (sink), or (2) the availability of a True Random Number Generator (TRNG) on each sensor. Neither assumption is realistic in large-scale Unattended Wireless Sensor Networks (UWSNs) composed of low-cost commodity sensors. periodic visits by the sink.) Previous work has demonstrated that sensor collaboration is an effective, yet expensive, means of attaining intrusion-resilience in UWSNs. In this paper, we explore intrusion resilience in Mobile UWSNs in the presence of a powerful mobile adversary. We show how the choice of the sensor mobility model influences intrusion resilience with respect to this adversary. We also explore self healing protocols that require only local communication. Results indicate that sensor density and neighborhood variability are the two key parameters affecting intrusion resilience. Our findings are supported by extensive analyses and simulations.

A new real time loss tolerant video streaming authentication scheme is presented. The bandwidth overhead is negligible, and authentication information are transmitted from the sender to all the receivers by means of a watermarking technique. Real time constraints are achieved by using a features computation algorithm, the sender embeds in each block of pictures the features computed over the current block, and a message authentication code that authenticates them. The receiver computes the features over the received block and compares it with that ones authenticated and extracted from the current block.

We present a measurement-based model of the frame error process on a Wi-Fi channel in rural environments. Measures are obtained in controlled conditions, and careful statistical analysis is performed on the data, providing information which the network simulation literature is lacking. Results indicate that most network simulators use a frame loss model that can miss important transmission impairments even at a short distance, particularly when considering antenna radiation pattern anisotropy and multi-rate switching.

With the development of broadcast wireless net- works high efficiency of wireless video transmission has been received increasingly greater attentions than before. Multimedia streaming services via hybrid networks, constituted by terrestrial wireless networks linked together by satellite, present major challenge in the management of network bandwidth. In this paper we propose a novel approach based on a packet level and a bit level FEC for improving the quality of service of multicast video streaming. We performed an extensive measurement campaign in an indoor scenario evaluating a statistical description of the bit error distribution for the terrestrial wireless link. We show that a bit level FEC can decrease the bandwidth wasting due to the application of an upper layer FEC only. Finally, we evaluate the performance of our approach in terms of recovered packets, bandwidth saving, and video quality.

We consider the problem of source authentication of video streams in multicast environments. We proposed a novel algorithm which combines signature amortization based on hash chains and watermarking to embed hash chains in the video stream. The algorithm exploits a novel watermarking procedure using Reed-Solomon mark encoding which ensures error-free and fast convergence mark extraction. We show that the algorithm has a negligible impact on the video stream quality and we evaluate the configuration parameters of the algorithm which ensure proper verification of the source authenticity.

Commonly used frame loss models for simulations over Wi-Fi channels assume a simple double regression model with threshold. This model is widely accepted, but few mea- surements are available in the literature that try to validate this commonly used model. As far as we know, none of them is based on field trials at the frame level. We present a series of measurements for relating transmission distance and packet loss on a Wi-Fi network in rural areas and propose a model that relates distance with packet loss probability. We show that a simple double regression propagation model like the one used in the ns-2 simulator can miss important transmission impairments that are apparent even at short transmitter-receiver distances. Measurements also show that packet loss at the frame level is a Bernoullian process for time spans of few seconds. We relate the packet loss probability to the received signal level using standard models for additive white Gaussian noise channels. The resulting model is much more similar to the measured channels than the simple models where all packets are received when the distance is below a given threshold and all are lost when the threshold is exceeded.

Satellite link presents peculiar characteristics like no packet reordering and low bit error rate. In this paper we leverage these characteristics combined with watermarking techniques to propose a novel authentication algorithm for multicast video streaming. This algorithm combines a single digital signature with a hash chain pre-computed on the transmitter side; the hash chain is embedded in the video stream by means of a watermarking technique. Our proposal shows several interesting features: Authentication is enforced, as well as integrity of the received multicast stream; received blocks can be authenticated on the fly; no storage is required on the receiver side, except for the amount of memory needed to store a single hash; overhead computations required on the receiver sum up to single hash per block, while a digital signature verification is amortized over the whole received stream. Finally, note that the bandwidth overhead introduced is negligible, since the applied watermarking technique introduces virtually no modifications (at least, not recognizable by humans) on the original video stream pictures. © 2007 IEEE.