Chitra Javali

Mobility independent secret key generation for wearable health-care devices

Security in Wireless Body Area Networks (WBAN) is of major concern as the miniature personal health-care devices need to protect the sensitive health information transmitted in wireless medium. It is essential for these devices to generate the shared secret key used for data encryption periodically. Recent studies have exploited wireless channel characteristics, e.g., received signal strength indicator (RSSI) to derive the shared secret key during random body movement of subject wearing devices. However, in the absence of node mobility, these schemes have very low bit rate capacity, and fail to derive keys with good entropy, which is a big threat for security. In this work, we study the effectiveness of combining dual antennas and frequency diversity for obtaining uncorrelated channel samples to improve entropy of key and bit rate in static channel conditions. We propose a novel mobility independent RSSI based secret key generation protocol -- iARC for WBAN. We conduct an extensive set of experiments in real time environments on sensor platforms used in WBAN to validate the performance of iARC. iARC has 800 bps secrecy capacity and generates 128 bit key in only 160 ms.

SeAK: Secure Authentication and Key Generation Protocol Based on Dual Antennas for Wireless Body Area Networks

The increasing interest in the usage of wireless body area networks (WBAN) in healthcare and other critical applications underscores the importance of secure communication among the body sensor devices. Associating an unknown device with an existing network without prior knowledge of a secret key poses a major challenge. Existing authentication schemes in WBAN are typically based on received signal strength (RSS). However, RSS techniques using a single antenna are susceptible to environmental factors and are vulnerable to attacks that use variable transmission power. We present SeAK, the first secure light-weight device pairing protocol for WBAN based on RSS obtained by dual-antenna transceivers utilizing spatial diversity. With spatially separated antennas, the RSS values from a nearby device are large and distinct, as opposed to those from a far-away device. SeAK exploits this effect to accomplish authentication and shared secret key generation simultaneously. We have implemented a prototype of SeAK on the Opal sensor platform with a 2.4 GHz compatible RF231 radio. We demonstrate that our protocol is able to achieve a 100 % success acceptance rate, securely authenticate a nearby device and generate a 128-bit secret key in 640 ms, as opposed to 15.9 s in other recent RSS-based schemes (e.g. ASK-BAN).

DLINK: Dual link based radio frequency fingerprinting for wearable devices

Exploiting unique wireless channel characteristics like signal strength for secret key generation has been recently studied by researchers. These schemes are lightweight and suitable for resource constrained wearable devices. However, a major drawback of existing schemes is that the successive channel samples with small sampling interval will have high correlation in time. This reduces the entropy and bit rate of keys. In this paper, we present dual-link based Radio Frequency fingerprinting solution - DLINK, which dynamically identifies the suitable multipath link to generate secret keys with improved entropy and bit rate in fast as well as slow fading channel conditions. We conduct an extensive set of experiments with real sensor devices mounted on subjects in multiple indoor environments. Our results show that, DLINK reduces the correlation of successive channel samples by 67%, and has 5 times higher bit rate, and improved entropy in all channel conditions compared to existing solutions.

Secure key generation and distribution protocol for wearable devices

Smart wearable devices have enormous applications in todays world and hence their usage is increasing significantly. As these devices communicate using wireless medium, the communication must be protected from eavesdropping by using shared secret keys for data encryption. In many applications, it is essential to use a common secret key for secured communication among multiple devices. In this paper, we present our novel secret key generation and distribution protocol exploiting accelerometer data collected from smart wearable devices. We propose (i) source separation method for processing accelerometer sensor data, and (ii) key distribution protocol based on Fuzzy vault. Our scheme is information theoretically secure and our experimental results show that the maximum key generation rate of our scheme is 50 bps which is suitable for practical applications.

Poster: Were You in the Cafe Yesterday?: Location Proof Generation & Verification for Mobile Users

In recent years, Location Based Services (LBS) and related applications are gaining popularity for providing access to the resources. LBS can either increase or decrease the access privileges of the users based on their location. Current mobile devices lack the intelligence to prove their location when requested. In this paper, we propose our novel solution for generating location proof for mobile users leveraging unique wireless characteristics and verification of the location claim by application services.

Secret key generation by virtual link estimation

In recent years, researchers have explored using unique radio propagation characteristics between two devices for extracting symmetric keys. However, the state-of-the-art has the following limitations: (i) paying more attention to only when the two devices are in communication range, and (ii) generating keys only when the devices are in motion. Secret key generation for devices which are not in communication range and for stationary nodes is quite a challenging task. In this paper, we study the feasibility of generating secret keys between two devices which do not possess any direct link with the help of a trusted relay. We propose and implement our protocol using off-the-shelf commercially available resource constrained devices suitable for health-care applications which are a vital part of pervasive networks. We conduct an extensive set of experiments in an indoor environment for various scenarios involving stationary and mobile nodes. Our results show that the key generation rate increases by 20 times compared to the existing mechanisms using the same sampling frequency. We analyse the mutual information shared between the legitimate devices and eavesdroppers and our results reveal that, when at least any two of the three legitimate devices are mobile, an eavesdropper cannot obtain sufficient useful information to guess the shared keys.

iARC: Secret Key Generation for Resource Constrained Devices by Inducing Artificial Randomness in the Channel

The existing secret key generation schemes for body-worn devices using wireless channel characteristics, e.g., received signal strength indicator (RSSI) are dependent on the node mobility and have very low bit rate. In this work, we propose a novel mobility independent RSSI based secret key generation protocol - iARC, which induces artificial randomness in the channel by employing dual antennas and dynamic frequency hopping effectively.

Gait-Key: A Gait-Based Shared Secret Key Generation Protocol for Wearable Devices

Recent years have witnessed a remarkable growth in the number of smart wearable devices. For many of these devices, an important security issue is to establish an authenticated communication channel between legitimate devices to protect the subsequent communications. Due to the wireless nature of the communication and the extreme resource constraints of sensor devices, providing secure, efficient, and user-friendly device pairing is a challenging task. Traditional solutions for device pairing mostly depend on key predistribution, which is unsuitable for wearable devices in many ways. In this article, we design Gait-Key, a shared secret key generation scheme that allows two legitimate devices to establish a common cryptographic key by exploiting users’ walking characteristics (gait). The intuition is that the sensors on different locations on the same body experience similar accelerometer signals when the user is walking. However, one main challenge is that the accelerometer also captures motion signals produced by other body parts (e.g., swinging arms). We address this issue by using the blind source separation technique to extract the informative signal produced by the unique gait patterns. Our experimental results show that Gait-Key can generate a common 128-bit key for two legitimate devices with 98.3% probability. To demonstrate the feasibility, the proposed key generation scheme is implemented on modern smartphones. The evaluation results show that the proposed scheme can run in real time on modern mobile devices and incurs low system overhead.

I Am Alice, I Was in Wonderland: Secure Location Proof Generation and Verification Protocol

In recent years, the proliferation of wireless devices has contributed to the emergence of new set of applications termed as Location Based Services (LBS). LBS provide privileges to mobile users based on their proximity to a facility. In order to gain benefits, users may lie or falsely claim their location. Hence, it is essential to verify the legitimacy of users. In this paper, we propose our novel solution for generating location proof for mobile users and verification of the location claim by application services. Our protocol exploits unique Wi-Fi signal characteristics and employs an information theoretically secure fuzzy vault scheme. We provide a detailed theoretical and experimental evaluation of our protocol. Our solution is faster by an order of magnitude, and the performance of our scheme is independent of the location tag size and distance between the mobile user and location proof provider compared to the state-of-the-art.

Accelerometer and Fuzzy Vault-Based Secure Group Key Generation and Sharing Protocol for Smart Wearables

The increased usage of smart wearables in various applications, specifically in health-care, emphasizes the need for secure communication to transmit sensitive health-data. In a practical scenario, where multiple devices are carried by a person, a common secret key is essential for secure group communication. Group key generation and sharing among wearables have received very little attention in the literature due to the underlying challenges: 1) difficulty in obtaining a good source of randomness to generate strong cryptographic keys, and 2) finding a common feature among all the devices to share the key. In this paper, we present a novel solution to generate and distribute group secret keys by exploiting on-board accelerometer sensor and the unique walking style of the user, i.e., gait. We propose a method to identify the suitable samples of accelerometer data during all routine activities of a subject to generate the keys with high entropy. In our scheme, the smartphone placed on waist employs fuzzy vault, a cryptographic construct, and utilizes the acceleration due to gait, a common characteristic extracted on all wearable devices to share the secret key. We implement our solution on commercially available off-the-shelf smart wearables, measure the system performance, and conduct experiments with multiple subjects. Our results demonstrate that the proposed solution has a bit rate of 750 b/s, low system overhead, distributes the key securely and quickly to all legitimate devices, and is suitable for practical applications.