A Mobile Secure Bluetooth-Enabled Cryptographic Provider

The use of digital X509v3 public key certificates, together with different standards for secure digital signatures are commonly adopted to establish authentication proofs between principals, applications and services. One of the robustness characteristics commonly associated with such mechanisms is the need of hardware-sealed cryptographic devices, such as Hardware-Security Modules (or HSMs), smart cards or hardware-enabled tokens or dongles. These devices support internal functions for management and storage of cryptographic keys, allowing the isolated execution of cryptographic operations, with the keys or related sensitive parameters never exposed. The portable devices most widely used are USB-tokens (or security dongles) and internal ships of smart cards (as it is also the case of citizen cards, banking cards or ticketing cards). More recently, a new generation of Bluetooth-enabled smart USB dongles appeared, also suitable to protect cryptographic operations and digital signatures for secure identity and payment applications. The common characteristic of such devices is to offer the required support to be used as secure cryptographic providers. Among the advantages of those portable cryptographic devices is also their portability and ubiquitous use, but, in consequence, they are also frequently forgotten or even lost. USB-enabled devices imply the need of readers, not always and not commonly available for generic smartphones or users working with computing devices. Also, wireless-devices can be specialized or require a development effort to be used as standard cryptographic providers. An alternative to mitigate such problems is the possible adoption of conventional Bluetooth-enabled smartphones, as ubiquitous cryptographic providers to be used, remotely, by client-side applications running in users’ devices, such as desktop or laptop computers. However, the use of smartphones for safe storage and management of private keys and sensitive parameters requires a careful analysis on the adversary model assumptions. The design options to implement a practical and secure smartphone-enabled cryptographic solution as a product, also requires the approach and the better use of the more interesting facilities provided by frameworks, programming environments and mobile operating systems services. In this dissertation we addressed the design, development and experimental evaluation of a secure mobile cryptographic provider, designed as a mobile service provided in a smartphone. The proposed solution is designed for Android-Based smartphones and supports on-demand Bluetooth-enabled cryptographic operations, including standard digital signatures. The addressed mobile cryptographic provider can be used by applications running on Windows-enabled computing devices, requesting digital signatures. The solution relies on the secure storage of private keys related to X509v3 public certificates and Android-based secure elements (SEs). With the materialized solution, an application running in a Windows computing device can request standard digital signatures of documents, transparently executed remotely by the smartphone regarded as a standard cryptographic provider

Secret Key Generation Based on AoA Estimation for Low SNR Conditions

In the context of physical layer security, a physical layer characteristic is used as a common source of randomness to generate the secret key. Therefore an accurate estimation of this characteristic is the core for reliable secret key generation. Estimation of almost all the existing physical layer characteristic suffer dramatically at low signal to noise (SNR) levels. In this paper, we propose a novel secret key generation algorithm that is based on the estimated angle of arrival (AoA) between the two legitimate nodes. Our algorithm has an outstanding performance at very low SNR levels. Our algorithm can exploit either the Azimuth AoA to generate the secret key or both the Azimuth and Elevation angles to generate the secret key. Exploiting a second common source of randomness adds an extra degree of freedom to the performance of our algorithm. We compare the performance of our algorithm to the algorithm that uses the most commonly used characteristics of the physical layer which are channel amplitude and phase. We show that our algorithm has a very low bit mismatch rate (BMR) at very low SNR when both channel amplitude and phase based algorithm fail to achieve an acceptable BMR

A Survey on Secret Key Extraction Using Received Signal Strength in Wireless Networks

Secure wireless communications typically rely on secret keys, which are difficult to establish in an ad hoc network without a key management infrastructure. The channel reciprocity and spatial decorrelation properties can be used to extract secret key, especially in a Rayleigh fading channel. But the intervention of intermediate objects between the communication nodes reduces the strength of the secret key generated through such methods. Furthermore, the impact of small fluctuations also reduces the bit matching rate of such key agreement methods. This paper is based on the survey conducted on secret key generation from Received Signal Strength (RSS). By consider ing uniqueness property of RSS as base, various authors have proposed different methods for secret key extraction. Due to use of RSS for key extraction the existing systems suffer from predictable filter response at random period. The existing system also faces signal fading and drop in RSS because of intermediate object. By this survey we specify that even after generating high entropy bits for key extraction, there are considerable drawbacks in extracted key du e to intervention of intermediate objects and remarkable fading and drop in RSS

Robust secret key capacity for the MIMO induced source model

This paper considers the problem of distilling a secret key in a Gaussian multiple-input multiple-output (MIMO) scenario with two legitimate nodes and an eavesdropper. Focusing on the realistic case without perfect knowledge of the eavesdropper channel, and following a conservative practical approach based on the maximization of the worst case secret key capacity (SKC), the problem of designing the optimal transmit covariance matrix is reformulated as a convex optimization problem. In the limiting case in which the eavesdropper channel can not be estimated, or when the estimate is highly unreliable, the optimal covariance matrix can be obtained by means of waterfilling or matched filtering like algorithms. Additionally, we illustrate the benefits of allowing time sharing between transmissions of the two legitimate nodes, and provide an efficient algorithm for obtaining the optimal transmit covariance matrices and time-sharing factor.This work was supported by the Spanish Government, Ministerio de Ciencia e Innovación (MICINN), under projects COSIMA (TEC2010-19545-C04-03) and COMONSENS (CSD2008-00010, CONSOLIDER INGENIO 2010 Program)

Channel Secondary Random Process for Robust Secret Key Generation

The broadcast nature of wireless communications imposes the risk of information leakage to adversarial users or unauthorized receivers. Therefore, information security between intended users remains a challenging issue. Most of the current physical layer security techniques exploit channel randomness as a common source between two legitimate nodes to extract a secret key. In this paper, we propose a new simple technique to generate the secret key. Specifically, we exploit the estimated channel to generate a secondary random process (SRP) that is common between the two legitimate nodes. We compare the estimated channel gain and phase to a preset threshold. The moving differences between the locations at which the estimated channel gain and phase exceed the threshold are the realization of our SRP. We simulate an orthogonal frequency division multiplexing (OFDM) system and show that our proposed technique provides a drastic improvement in the key bit mismatch rate (BMR) between the legitimate nodes when compared to the techniques that exploit the estimated channel gain or phase directly. In addition to that, the secret key generated through our technique is longer than that generated by conventional techniques

The Mason Test: A Defense Against Sybil Attacks in Wireless Networks Without Trusted Authorities

Wireless networks are vulnerable to Sybil attacks, in which a malicious node poses as many identities in order to gain disproportionate influence. Many defenses based on spatial variability of wireless channels exist, but depend either on detailed, multi-tap channel estimation - something not exposed on commodity 802.11 devices - or valid RSSI observations from multiple trusted sources, e.g., corporate access points - something not directly available in ad hoc and delay-tolerant networks with potentially malicious neighbors. We extend these techniques to be practical for wireless ad hoc networks of commodity 802.11 devices. Specifically, we propose two efficient methods for separating the valid RSSI observations of behaving nodes from those falsified by malicious participants. Further, we note that prior signalprint methods are easily defeated by mobile attackers and develop an appropriate challenge-response defense. Finally, we present the Mason test, the first implementation of these techniques for ad hoc and delay-tolerant networks of commodity 802.11 devices. We illustrate its performance in several real-world scenarios

Fingerprinting Smart Devices Through Embedded Acoustic Components

The widespread use of smart devices gives rise to both security and privacy concerns. Fingerprinting smart devices can assist in authenticating physical devices, but it can also jeopardize privacy by allowing remote identification without user awareness. We propose a novel fingerprinting approach that uses the microphones and speakers of smart phones to uniquely identify an individual device. During fabrication, subtle imperfections arise in device microphones and speakers which induce anomalies in produced and received sounds. We exploit this observation to fingerprint smart devices through playback and recording of audio samples. We use audio-metric tools to analyze and explore different acoustic features and analyze their ability to successfully fingerprint smart devices. Our experiments show that it is even possible to fingerprint devices that have the same vendor and model; we were able to accurately distinguish over 93% of all recorded audio clips from 15 different units of the same model. Our study identifies the prominent acoustic features capable of fingerprinting devices with high success rate and examines the effect of background noise and other variables on fingerprinting accuracy