An important open problem in the area of Traitor Tracing is designing a scheme with constant expansion of the size of keys (users' keys and the encryption key) and of the size of ciphertexts with respect to the size of the plaintext. This problem is known from the introduction of Traitor Tracing by Chor, Fiat and Naor. We refer to such schemes as traitor tracing with constant transmission rate. Here we present a general methodology and two protocol constructions that result in the first two public-key traitor tracing schemes with constant transmission rate in settings where plaintexts can be calibrated to be sufficiently large. Our starting point is the notion of copyrighted function which was presented by Naccache, Shamir and Stern. We first solve the open problem of discrete-log-based and public-key-based copyrighted function. Then, we observe the simple yet crucial relation between (public-key) copyrighted encryption and (public-key) traitor tracing, which we exploit by introducing a generic design paradigm for designing constant transmission rate traitor tracing schemes based on copyrighted encryption functions. Our first scheme achieves the same expansion efficiency as regular ElGamal encryption. The second scheme introduces only a slightly larger (constant) overhead, however, it additionally achieves efficient black-box traitor tracing (against any pirate construction).

Traitor Tracing with constant transmission rate

Internet of Things (IoT), also referred to as the Internet of Objects, is envisioned as a transformative approach for providing numerous services. Compact smart devices constitute an essential part of IoT. They range widely in use, size, energy capacity, and computation power. However, the integration of these smart things into the standard Internet introduces several security challenges because the majority of Internet technologies and communication protocols were not designed to support IoT. Moreover, commercialization of IoT has led to public security concerns, including personal privacy issues, threat of cyber attacks, and organized crime. In order to provide a guideline for those who want to investigate IoT security and contribute to its improvement, this survey attempts to provide a comprehensive list of vulnerabilities and countermeasures against them on the edge-side layer of IoT, which consists of three levels: (i) edge nodes, (ii) communication, and (iii) edge computing. To achieve this goal, we first briefly describe three widely-known IoT reference models and define security in the context of IoT. Second, we discuss the possible applications of IoT and potential motivations of the attackers who target this new paradigm. Third, we discuss different attacks and threats. Fourth, we describe possible countermeasures against these attacks. Finally, we introduce two emerging security challenges not yet explained in detail in previous literature.

A Comprehensive Study of Security of Internet-of-Things

Keystroke privacy is critical for ensuring the security of computer systems and the privacy of human users as what being typed could be passwords or privacy sensitive information. In this paper, we show for the first time that WiFi signals can also be exploited to recognize keystrokes. The intuition is that while typing a certain key, the hands and fingers of a user move in a unique formation and direction and thus generate a unique pattern in the time-series of Channel State Information (CSI) values, which we call CSI-waveform for that key. In this paper, we propose a WiFi signal based keystroke recognition system called WiKey. WiKey consists of two Commercial Off-The-Shelf (COTS) WiFi devices, a sender (such as a router) and a receiver (such as a laptop). The sender continuously emits signals and the receiver continuously receives signals. When a human subject types on a keyboard, WiKey recognizes the typed keys based on how the CSI values at the WiFi signal receiver end. We implemented the WiKey system using a TP-Link TL-WR1043ND WiFi router and a Lenovo X200 laptop. WiKey achieves more than 97.5\% detection rate for detecting the keystroke and 96.4% recognition accuracy for classifying single keys. In real-world experiments, WiKey can recognize keystrokes in a continuously typed sentence with an accuracy of 93.5%.

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Keystroke Recognition Using WiFi Signals

Security is oftentimes centrally managed. An alternative trend of using collaboration in order to improve security has gained momentum over the past few years. Collaborative security is an abstract concept that applies to a wide variety of systems and has been used to solve security issues inherent in distributed environments. Thus far, collaboration has been used in many domains such as intrusion detection, spam filtering, botnet resistance, and vulnerability detection. In this survey, we focus on different mechanisms of collaboration and defense in collaborative security. We systematically investigate numerous use cases of collaborative security by covering six types of security systems. Aspects of these systems are thoroughly studied, including their technologies, standards, frameworks, strengths and weaknesses. We then present a comprehensive study with respect to their analysis target, timeliness of analysis, architecture, network infrastructure, initiative, shared information and interoperability. We highlight five important topics in collaborative security, and identify challenges and possible directions for future research. Our work contributes the following to the existing research on collaborative security with the goal of helping to make collaborative security systems more resilient and efficient. This study (1) clarifies the scope of collaborative security, (2) identifies the essential components of collaborative security, (3) analyzes the multiple mechanisms of collaborative security, and (4) identifies challenges in the design of collaborative security.

/pdf/collaborative-security-a-survey-and-taxonomy-43p8xo3t4g.pdf

Collaborative Security: A Survey and Taxonomy

Attacks that use side channels, such as sound and electromagnetic emanation, to infer keystrokes on physical keyboards are ineffective on smartphones without physical keyboards. We describe a new side channel, motion, on touch screen smartphones with only soft keyboards. Since typing on different locations on the screen causes different vibrations, motion data can be used to infer the keys being typed. To demonstrate this attack, we developed TouchLogger, an Android application that extracts features from device orientation data to infer keystrokes. TouchLogger correctly inferred more than 70% of the keys typed on a number-only soft keyboard on a smartphone. We hope to raise the awareness of motion as a significant side channel that may leak confidential data.

/pdf/touchlogger-inferring-keystrokes-on-touch-screen-from-3ggxkazvvn.pdf

TouchLogger: inferring keystrokes on touch screen from smartphone motion

Computer keyboards are often used to transmit confidential data such as passwords. Since they contain electronic components, keyboards eventually emit electromagnetic waves. These emanations could reveal sensitive information such as keystrokes. The technique generally used to detect compromising emanations is based on a wide-band receiver, tuned on a specific frequency. However, this method may not be optimal since a significant amount of information is lost during the signal acquisition. Our approach is to acquire the raw signal directly from the antenna and to process the entire captured electromagnetic spectrum. Thanks to this method, we detected four different kinds of compromising electromagnetic emanations generated by wired and wireless keyboards. These emissions lead to a full or a partial recovery of the keystrokes. We implemented these sidechannel attacks and our best practical attack fully recovered 95% of the keystrokes of a PS/2 keyboard at a distance up to 20 meters, even through walls. We tested 12 different keyboard models bought between 2001 and 2008 (PS/2, USB, wireless and laptop). They are all vulnerable to at least one of the four attacks. We conclude that most of modern computer keyboards generate compromising emanations (mainly because of the manufacturer cost pressures in the design). Hence, they are not safe to transmit confidential information.

/pdf/compromising-electromagnetic-emanations-of-wired-and-2taytvuitx.pdf

Compromising electromagnetic emanations of wired and wireless keyboards

Key agreement protocols are frequently based on the Diffie-Hellman protocol but require authenticating the protocol messages in two ways. This can be made by a cross-authentication protocol. Such protocols, based on the assumption that a channel which can authenticate short strings is available (SAS-based), have been proposed by Vaudenay. In this paper, we survey existing protocols and we propose a new one. Our proposed protocol requires three moves and a single SAS to be authenticated in two ways. It is provably secure in the random oracle model. We can further achieve security with a generic construction (e.g. in the standard model) at the price of an extra move. We discuss applications such as secure peer-to-peer VoIP.

/pdf/sas-based-authenticated-key-agreement-4qb04b879o.pdf

SAS-Based authenticated key agreement

The techniques generally used to detect compromising emanations are based on a wide-band receiver tuned on a specific frequency or a spectral analyzer with a limited bandwidth However, these methods may not be optimal since a significant amount of information is lost during the signal acquisition In this paper, we propose a straightforward but efficient approach which acquires raw signal directly from the antenna and processes the entire captured electromagnetic spectrum thanks to the computation of short time Fourier transforms We applied this approach to detect potential compromising electromagnetic emanations radiated by modern keyboard Since keyboards are often used to transmit confidential data such as passwords, these emanations could remotely reveal sensitive information such as keystrokes Thanks to this method, we detected four different kinds of compromising electromagnetic emanations generated by wired and wireless keyboards These emissions lead to a full or a partial recovery of the keystrokes We implemented these side-channel attacks and our best practical attack fully recovered 95% of the keystrokes of a PS/2 keyboard at a distance up to 20 meters, even through walls

/pdf/an-improved-technique-to-discover-compromising-yfmjkj3rs3.pdf

An improved technique to discover compromising electromagnetic emanations

Vaudenay recently proposed a message authentication protocol which is interactive and based on short authenticated strings (SAS). We study here SAS-based non-interactive message authentication protocols (NIMAP). We start by the analysis of two popular non-interactive message authentication protocols. The first one is based on a collision-resistant hash function and was presented by Balfanz et al. The second protocol is based on a universal hash function family and was proposed by Gehrmann, Mitchell, and Nyberg. It uses much less authenticated bits but requires a stronger authenticated channel.

We propose a protocol which can achieve the same security as the first protocol but using less authenticated bits, without any stronger communication model, and without requiring a hash function to be collision-resistant. Finally, we demonstrate the optimality of our protocol.

/pdf/an-optimal-non-interactive-message-authentication-protocol-4nz1lci6jm.pdf

An optimal non-interactive message authentication protocol

New trends in consumer electronics have created a strong demand for fast, reliable and user-friendly key agreement protocols. However, many key agreement protocols are secure only against passive attacks. Therefore, message authentication is often unavoidable in order to achieve security against active adversaries. Pasini and Vaudenay were the first to propose a new compelling methodology for message authentication. Namely, their two-party protocol uses short authenticated strings (SAS) instead of pre-shared secrets or public-key infrastructure that are classical tools to achieve authenticity. In this article, we generalise this methodology for multi-party settings. We give a new group message authentication protocol that utilises only limited authenticated communication and show how to combine this protocol with classical key agreement procedures. More precisely, we describe how to transform any group key agreement protocol that is secure against passive attacks into a new protocol that is secure against active attacks.

/pdf/sas-based-group-authentication-and-key-agreement-protocols-1yfk7gcqka.pdf

Sylvain Pasini

Papers

Compromising electromagnetic emanations of wired and wireless keyboards

SAS-Based authenticated key agreement

An improved technique to discover compromising electromagnetic emanations

An optimal non-interactive message authentication protocol

SAS-based group authentication and key agreement protocols