Current mechanisms for authenticating communication between devices that share no prior context are inconvenient for ordinary users, without the assistance of a trusted authority. We present and analyze Seeing-Is-Believing, a system that utilizes 2D barcodes and cameraphones to implement a visual channel for authentication and demonstrative identification of devices. We apply this visual channel to several problems in computer security, including authenticated key exchange between devices that share no prior context, establishment of a trusted path for configuration of a TCG-compliant computing platform, and secure device configuration in the context of a smart home. 1.

Authentication of communication channels between devices that lack any previous association is an challenging problem. It has been considered in many contexts and in various flavors, most recently, by McCune et al., where human-assisted device authentication is achieved through the use of photo cameras (present in some cellphones) and 2-dimensional barcodes. Their proposed Seeing-is-Believing system allows users with devices equipped with cameras to use the visual channel for authentication of unfamiliar devices, so as to defeat man-inthe-middle attacks. In this paper, we investigate an alternative and complementary approach—the use of the audio channel for humanassisted authentication of previously un-associated devices. Our motivation is three-fold: (1) many personal devices are not equipped with cameras or scanners, (2) some human users are visually impaired (hence, cannot be in the authentication pipeline of a vision-based system), and (3) some usage scenarios preclude either taking a sufficiently clear picture and/or the use of barcodes. We develop and evaluate a system we call Loud-and-Clear (L&C) authentication, which, like Seeing-is-Believing, places little demand on the human user. The L&C system is based on the use of a text-to-speech engine to read an auditoriallyrobust, grammatically-correct pass-phrase derived from an authentication string that is to be used by peer devices. In particular, by coupling the auditory reading of the one-way hash of an authentication string on one device with the display of of this text on another device, we demonstrate that L&C is suitable for secure device pairing (e.g., key exchange) and similar tasks. We also describe several use cases, as well as provide some performance data for a prototype implementation and a discussion of the security properties of L&C. 1

Abstract. Solutions for an easy and secure setup of a wireless connection between two devices are urgently needed for WLAN, Wireless USB, Bluetooth and similar standards for short range wireless communication. All such key exchange protocols employ data authentication as an unavoidable subtask. As a solution, we propose an asymptotically optimal protocol family for data authentication that uses short manually authenticated out-of-band messages. Compared to previous articles by Vaudenay and Pasini the results of this paper are more general and based on weaker security assumptions. In addition to providing security proofs for our protocols, we focus also on implementation details and propose practically secure and efficient sub-primitives for applications. 1

Abstract. Setting up security associations between end-user devices is a challenging task when it needs to be done by ordinary users. The increasing popularity of powerful personal electronics with wireless communication abilities has made the problem more urgent than ever before. During the last few years, several solutions have appeared in the research literature. Several standardization bodies have also been working on improved setup procedures. All these protocols provide certain level of security, but several new questions arise, such as ”how to implement this protocol so that it is easy to use? ” and ”is it still secure when used by a non-technical person? ” In this paper, we attempt to answer these questions by carrying out a comparative usability evaluation of selected methods to derive some insights into the usability and security of these methods as well as strategies for implementing them. 1

Recently several researchers and practitioners have begun to address the problem of how to set up secure communication between two devices without the assistance of a trusted third party. McCune, et al. [4] proposed that one device displays the hash of its public key in the form of a barcode, and the other device reads it using a camera. Mutual authentication requires switching the roles of the devices and repeating the above process in the reverse direction. In this paper, we show how strong mutual authentication can be achieved even with a unidirectional visual channel, without having to switch device roles. By adopting recently proposed improved pairing protocols, we propose how visual channel authentication can be used even on devices that have very limited displaying capabilities.

Abstract. Small, mobile devices without user interfaces, such as Bluetooth headsets, often need to communicate securely over wireless networks. Active attacks can only be prevented by authenticating wireless communication, which is problematic when devices do not have any a priori information about each other. We introduce a new method for device-to-device authentication by shaking devices together. This paper describes two protocols for combining cryptographic authentication techniques with known methods of accelerometer data analysis to the effect of generating authenticated, secret keys. The protocols differ in their design, one being more conservative from a security point of view, while the other allows more dynamic interactions. Three experiments are used to optimize and validate our proposed authentication method. 1

Abstract. 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 collisionresistant 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 collisionresistant. Finally, we demonstrate the optimality of our protocol. 1

Securing wireless channels necessitates authenticating communication partners. For spontaneous interaction, authentication must be efficient and intuitive. One approach to create interaction and authentication methods that scale to using hundreds of services throughout the day is to rely on personal, trusted, mobile devices to interact with the environment. Authenticating the resulting device-to-device interactions requires an out-of-band channel that is verifiable by the user. We present a protocol for creating such an out-of-band channel with visible laser light that is secure against man-in-the-middle attacks even when the laser transmission is not confidential. A prototype implementation shows that an appropriate laser channel can be constructed with simple off-the-shelf components. 1.

on human interaction

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