Ashraf Masood

Piezoresistivity in vapor‐deposited diamond films

We report the observation of a very large piezoresistive effect in both polycrystalline and homoepitaxial chemical‐vapor‐deposited diamond films. The gauge factor for polycrystalline p‐type diamond at 500 microstrains was found to be only 6 at room ambient, but increased rapidly with temperature, exceeding that of polycrystalline silicon (30) at 35 °C, and that of single‐crystal Si (120) at 50 °C. For strain and current flow in the [100] direction, the gauge factor of a (100)‐oriented homoepitaxial diamond film was found to be at least 550 at room temperature. Although the origins and unexpected temperature dependence of piezoresistive effect in diamond are not yet understood, these findings may suggest diamond‐based sensors with performance significantly superior to that of their Si counterparts.

An efficient key distribution scheme for heterogeneous sensor networks

Key distribution refers to the problem of establishing shared secrets on sensor nodes such that secret symmetric keys for communication privacy, integrity and authenticity can be generated. In a wireless sensor network, pre-distribution of secret keys is possibly the most practical approach to protect network communications but it is difficult due to the ad hoc nature, intermittent connectivity, and resource limitations of the sensor networks. In this paper, we propose a key distribution scheme based on random key pre-distribution for heterogeneous sensor network (HSN) to achieve better performance and security as compared to homogeneous network which suffer from high communication overhead, computation overhead, and/or high storage requirements. In a key generation process, instead of generating a large pool of random keys, a key pool is represented by a small number of generation keys. For a given generation key and publicly known seed value, a one-way hash function generates a key chain, and these key chains collectively make a key pool. Each sensor node is assigned a small number of randomly selected generation keys. The proposed scheme reduces the storage requirements while maintaining the same security strength.

Secure group communication with self-healing and rekeying in wireless sensor networks

We have developed a self-healing key distribution scheme for secure multicast group communications for wireless sensor network environment. We present a strategy for securely distributing rekeying messages and specify techniques for joining and leaving a group. Access control in multicast system is usually achieved by encrypting the content using an encryption key, known as the group key (session key) that is only known by the group controller and all legitimate group members. In our scheme, all rekeying messages, except for unicast of an individual key, are transmitted without any encryption using one-way hash function and XOR operation. In our proposed scheme, nodes are capable of recovering lost session keys on their own, without requesting additional transmission from the group controller. The proposed scheme provides both backward and forward secrecy. We analyze the proposed scheme to verify that it satisfies the security and performance requirements for secure group communication.

Techniques for Patterning of CVD Diamond Films on Non‐Diamond Substrates

Three techniques for patterning of CVD diamond films are developed. First, predeposition patterning is performed by standard lithography using photoresist mixed with fine diamond particles to act as seed crystals. Second, substrates are masked either before ultrasonic treatment with diamond powder (which promotes nucleation), and the mask removed before diamond growth, or masked after treatment but before diamond deposition. Third, patterning of continuous diamond thin films by selective etching in oxygen at 700°C has been performed in a rapid thermal processor using or as masking layer. The selectivity and resolution was found to be good in all cases.

Scalable and efficient key management for heterogeneous sensor networks

As typical wireless sensor networks (WSNs) have resource limitations, predistribution of secret keys is possibly the most practical approach for secure network communications. In this paper, we propose a key management scheme based on random key predistribution for heterogeneous wireless sensor networks (HSNs). As large-scale homogeneous networks suffer from high costs of communication, computation, and storage requirements, the HSNs are preferred because they provide better performance and security solutions for scalable applications in dynamic environments. We consider hierarchical HSN consisting of a small number high-end sensors and a large number of low-end sensors. To address storage overhead problem in the constraint sensor nodes, we incorporate a key generation process, where instead of generating a large pool of random keys, a key pool is represented by a small number of generation keys. For a given generation key and a publicly known seed value, a keyed-hash function generates a key chain; these key chains collectively make a key pool. As dynamic network topology is native to WSNs, the proposed scheme allows dynamic addition and removal of nodes. This paper also reports the implementation and the performance of the proposed scheme on Crossbow’s MicaZ motes running TinyOS. The results indicate that the proposed scheme can be applied efficiently in resource-constrained sensor networks. We evaluate the computation and storage costs of two keyed-hash algorithms for key chain generation, HMAC-SHA1 and HMAC-MD5.

Security Analysis of Ultra-lightweight Cryptographic Protocol for Low-cost RFID Tags: Gossamer Protocol

Gossamer protocol has been recently published to achieve mutual authentication in low-cost RFID tags. This protocol is considered to fall in ultra-lightweight class as it incorporates simple and low cost operations. Most of the earlier proposals in this class were exposed soon after their publication. Common weaknesses included use of Triangular functions and improper use of logic operators. Gossamer protocol used two non-triangular functions a) ROTbits and b) MIXbits. These functions provide confusion and diffusion properties and are implemented as cheaper operations. Thus, this protocol can be used for EPCglobal Class-1 Generation-2 standard (considered as universal standard for low-cost tags). This protocol is able to overcome existing weaknesses and is considered to be more attractive for low-capability devices as compared to earlier protocols of this class. In this paper, we analyze the security features provided by Gossamer protocol. The vulnerabilities discovered during this analysis reveal that different attacks including denial of service, memory and computation exhaustive, de-synchronization, replay, attack on data integrity and IDS (index pseudonym) collision are possible. As a consequence, we propose a new mutual authentication protocol keeping in mind the constraints and making use of the existing operations without addition of any expensive one. The analysis of the proposed protocol shows that it is resistant to all the attacks possible in case of Gossamer protocol. A comparative security analysis shows that proposed protocol provides better security features with a small compromise of communication overheads. Two additional public messages are exchanged between the reader and the tag to address the vulnerabilities present in Gossamer protocol.

Synthesis and electrical characterization of boron‐doped thin diamond films

Patterned semiconducting polycrystalline diamond films have been synthesized by hot‐filament CVD using in situ doping by pure boron powder. P‐type conduction was confirmed by both Hall and Seebeck effects. The quality of deposited films, as determined by SEM and Raman spectroscopy, was unaffected by the doping. The resistivity and Hall mobility measured by the Van der Pauw method were in the range of 20–100 Ω cm and 2–32 cm2 V−1 s−1, respectively. The dopant activation energies, as computed from the resistivity versus temperature curves (up to 300 °C), were in the range of 0.38–0.30 eV corresponding to Hall concentration in the range of 9×1015–2×1017 cm−3 and boron concentration in the range of 1017–1021 cm−3. The estimated impurity concentration is consistent with SIMS results.

Boron-doped vapor-deposited diamond temperature microsensors

Abstract Boron-doped chemical vapor deposition (CVD) diamond thermistors show temperature and response-time ranges of 80–1270 K and 0.29–25 μs, respectively. A reduction of the thermistor dimensions below 10 μm results in lithographic problems related to surface roughness of the diamond films. Using diamond nucleation densities in the range 108–1011 cm−2, the surface roughness is studied employing a second-generation multisensor diamond test chip with a minimum feature size of 5 μm. The chip is expected to help commercialize CVD diamond thermistors in the near term.

Key Management and Secure Routing in Heterogeneous Sensor Networks

Key management is very critical to security protocols, as encryption and authentication services are based on the operations involving keys. In this paper, we propose a key management scheme based on random key pre-distribution for heterogeneous sensor network (HSN) to achieve better performance and security as compared to homogeneous network which suffer from high communication overhead, computation overhead, and/or high storage requirements. In a key pre-distribution phase, all the keys of the key pool are assigned to H-sensors and only one key of that pool is assigned to L-sensor, which significantly reduce the storage requirements while providing the full network connectivity. Further a secure routing structure is also proposed as application of our proposed key management scheme. Analysis shows that the proposed scheme is more resilient against node capture as compare to other random key distribution schemes.

Algebraic Cryptanalysis of A NLFSR Based Stream Cipher

Among recent developments on stream ciphers, the algebraic attack has gained much attention. In this paper we concentrate on algebraic cryptanalysis of Grain, a non-linear feedback shift register (NLFSR) based stream cipher. The target here is to analyze generic key generating structure of Grain, that is why, we aim to recover the internal states of cipher rather than the key-bits. Experiments are carried out to solve these varying degree equations, with some guessed bits using Groebner basis technique. Our approach succeeds in recovering (approx) 1/2 of the internal stateAmong recent developments on stream ciphers, the algebraic attack has gained much attention. In this paper we concentrate on algebraic cryptanalysis of Grain, a non-linear feedback shift register (NLFSR) based stream cipher. The target here is to analyze generic key generating structure of Grain, that is why, we aim to recover the internal states of cipher rather than the key-bits. Experiments are carried out to solve these varying degree equations, with some guessed bits using Groebner basis technique. Our approach succeeds in recovering (approx) 1/2 of the internal state bits of Grain-1, while other half are guessed. While, in case of Grain-128, only 1/4 of the state bits can be obtained. bits of Grain-1, while other half are guessed. While, in case of Grain-128, only 1/4 of the state bits can be obtained.