5 research outputs found
Providing Physical Layer Security for Mission Critical Machine Type Communication
The design of wireless systems for Mission Critical Machine Type
Communication (MC-MTC) is currently a hot research topic. Wireless systems are
considered to provide numerous advantages over wired systems in industrial
applications for example. However, due to the broadcast nature of the wireless
channel, such systems are prone to a wide range of cyber attacks. These range
from passive eavesdropping attacks to active attacks like data manipulation or
masquerade attacks. Therefore it is necessary to provide reliable and efficient
security mechanisms. One of the most important security issue in such a system
is to ensure integrity as well as authenticity of exchanged messages over the
air between communicating devices in order to prohibit active attacks. In the
present work, an approach on how to achieve this goal in MC-MTC systems based
on Physical Layer Security (PHYSEC), especially a new method based on keeping
track of channel variations, will be presented and a proof-of-concept
evaluation is given
Exploiting Radio Channel Aware Physical Layer Concepts
In DS-CDMA, spreading sequences are allocated to users to separate different
links namely, the base-station to user in the downlink or the user to base station in the uplink. These sequences are designed for optimum periodic correlation properties. Sequences with good periodic auto-correlation properties help in frame synchronisation at the receiver while sequences with good periodic cross-
correlation property reduce cross-talk among users and hence reduce the interference among them. In addition, they are designed to have reduced implementation complexity so that they are easy to generate. In current systems, spreading sequences are allocated to users irrespective of their channel condition. In this thesis,
the method of allocating spreading sequences based on users’ channel condition
is investigated in order to improve the performance of the downlink. Different
methods of dynamically allocating the sequences are investigated including; optimum allocation through a simulation model, fast sub-optimum allocation through
a mathematical model, and a proof-of-concept model using real-world channel
measurements. Each model is evaluated to validate, improvements in the gain
achieved per link, computational complexity of the allocation scheme, and its impact on the capacity of the network.
In cryptography, secret keys are used to ensure confidentiality of communication between the legitimate nodes of a network. In a wireless ad-hoc network, the
broadcast nature of the channel necessitates robust key management systems for
secure functioning of the network. Physical layer security is a novel method of
profitably utilising the random and reciprocal variations of the wireless channel to
extract secret key. By measuring the characteristics of the wireless channel within
its coherence time, reciprocal variations of the channel can be observed between
a pair of nodes. Using these reciprocal characteristics of
common shared secret key is extracted between a pair of the nodes. The process
of key extraction consists of four steps namely; channel measurement, quantisation, information reconciliation, and privacy amplification. The reciprocal channel
variations are measured and quantised to obtain a preliminary key of vector bits (0; 1). Due to errors in measurement, quantisation, and additive Gaussian noise,
disagreement in the bits of preliminary keys exists. These errors are corrected
by using, error detection and correction methods to obtain a synchronised key at
both the nodes. Further, by the method of secure hashing, the entropy of the key
is enhanced in the privacy amplification stage. The efficiency of the key generation process depends on the method of channel measurement and quantisation.
Instead of quantising the channel measurements directly, if their reciprocity is enhanced and then quantised appropriately, the key generation process can be made efficient and fast. In this thesis, four methods of enhancing reciprocity are presented namely; l1-norm minimisation, Hierarchical clustering, Kalman filtering,
and Polynomial regression. They are appropriately quantised by binary and adaptive quantisation. Then, the entire process of key generation, from measuring the channel profile to obtaining a secure key is validated by using real-world channel measurements. The performance evaluation is done by comparing their performance in terms of bit disagreement rate, key generation rate, test of randomness,
robustness test, and eavesdropper test. An architecture, KeyBunch, for effectively
deploying the physical layer security in mobile and vehicular ad-hoc networks is
also proposed. Finally, as an use-case, KeyBunch is deployed in a secure vehicular communication architecture, to highlight the advantages offered by physical layer security
Exploiting Radio Channel Aware Physical Layer Concepts
In DS-CDMA, spreading sequences are allocated to users to separate different
links namely, the base-station to user in the downlink or the user to base station in the uplink. These sequences are designed for optimum periodic correlation properties. Sequences with good periodic auto-correlation properties help in frame synchronisation at the receiver while sequences with good periodic cross-
correlation property reduce cross-talk among users and hence reduce the interference among them. In addition, they are designed to have reduced implementation complexity so that they are easy to generate. In current systems, spreading sequences are allocated to users irrespective of their channel condition. In this thesis,
the method of allocating spreading sequences based on users’ channel condition
is investigated in order to improve the performance of the downlink. Different
methods of dynamically allocating the sequences are investigated including; optimum allocation through a simulation model, fast sub-optimum allocation through
a mathematical model, and a proof-of-concept model using real-world channel
measurements. Each model is evaluated to validate, improvements in the gain
achieved per link, computational complexity of the allocation scheme, and its impact on the capacity of the network.
In cryptography, secret keys are used to ensure confidentiality of communication between the legitimate nodes of a network. In a wireless ad-hoc network, the
broadcast nature of the channel necessitates robust key management systems for
secure functioning of the network. Physical layer security is a novel method of
profitably utilising the random and reciprocal variations of the wireless channel to
extract secret key. By measuring the characteristics of the wireless channel within
its coherence time, reciprocal variations of the channel can be observed between
a pair of nodes. Using these reciprocal characteristics of
common shared secret key is extracted between a pair of the nodes. The process
of key extraction consists of four steps namely; channel measurement, quantisation, information reconciliation, and privacy amplification. The reciprocal channel
variations are measured and quantised to obtain a preliminary key of vector bits (0; 1). Due to errors in measurement, quantisation, and additive Gaussian noise,
disagreement in the bits of preliminary keys exists. These errors are corrected
by using, error detection and correction methods to obtain a synchronised key at
both the nodes. Further, by the method of secure hashing, the entropy of the key
is enhanced in the privacy amplification stage. The efficiency of the key generation process depends on the method of channel measurement and quantisation.
Instead of quantising the channel measurements directly, if their reciprocity is enhanced and then quantised appropriately, the key generation process can be made efficient and fast. In this thesis, four methods of enhancing reciprocity are presented namely; l1-norm minimisation, Hierarchical clustering, Kalman filtering,
and Polynomial regression. They are appropriately quantised by binary and adaptive quantisation. Then, the entire process of key generation, from measuring the channel profile to obtaining a secure key is validated by using real-world channel measurements. The performance evaluation is done by comparing their performance in terms of bit disagreement rate, key generation rate, test of randomness,
robustness test, and eavesdropper test. An architecture, KeyBunch, for effectively
deploying the physical layer security in mobile and vehicular ad-hoc networks is
also proposed. Finally, as an use-case, KeyBunch is deployed in a secure vehicular communication architecture, to highlight the advantages offered by physical layer security
Not Available
Not AvailableThe Europeans started to come to India at the beginning
of the 16th century for trade. The Portuguese were the
first group of Europeans to reach the southwestern
coast of India in 1498 and establish their colonies.
They were also the last group of the Europeans to
leave the Indian territory after ruling a part of the
country for about 450 years. With their arrival, new
technology and warfare tactics were introduced in the
region. Associated with their artillery, preparation of
gunpowder as a new technology was introduced in
Goa. Gigantic sized millstones were used for the production
of gunpowder in Casa de Polvora, Panelim,
Goa. In 2007, when real estate developers commenced
their construction work at Casa de Polvora, the
Archaeological Survey of India salvaged the endangered
millstones from Panelim. The aim of the present
communication is to analyse the samples and to find
out whether the stone used was quarried from Dharavi
(Uttan; which was a part of Bassein territory of the
Portuguese) from where the Portuguese acquired
stones on a large scale for the decoration of churches
in Goa. To achieve this, archaeological, petrographic,
mineralogical and geochemical studies have been
carried out on samples of millstones and the quarried
site at Dharavi (Uttan). In addition sample was also
collected from cannon ball found at Arsenal (Old Goa)
to find out whether stone from Dharavi (Uttan) was
used. The analytical results suggest that the millstones
are made of limestone, the Dharavi (Uttan) stone is
more siliceous – and the cannon balls are made from
basalt.Not Availabl