1,297 research outputs found
A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications
Wireless channels are characterized by multipath and fading that can often cause long
burst of errors. Even though, to date, many very sophisticated error correcting codes have
been designed, yet none can handle long burst of errors efficiently. An interleaver, a
device that distributes a burst of errors, possibly caused by a deep fade, and makes them
appear as simple random errors, therefore, proves to a very useful technique when used in
conjunction with an efficient error correcting code.
In this work, a novel near optimal seed based random interleaver is designed. An optimal
interleaver scatters a given burst of errors uniformly over a fixed block of data - a
property that is measured by so called ‘spread’. The design makes use of a unique seed
based pseudo-random sequence generator or logistic map based chaotic sequence
generator to scramble the given block of data. Since the proposed design is based on a
seed based scrambler, the nature of input is irrelevant. Therefore, the proposed interleaver
can interleave either the bits or the symbols or the packets or even the frames.
Accordingly, in this work, we analyze the suitability of interleaver when introduced
before or after the modulation in single carrier communication systems and show that
interleaving the bits before modulation or interleaving the symbols after modulation has
same advantage. We further show that, in an orthogonal frequency division multiplexing
(OFDM) systems, the position of interleaver, whether before or after constellation
mapper, has no significance, and is interchangeable. However, scrambling symbols is
computationally less expensive than scrambling bits.
For the purpose of analyzing the performance of the proposed seed based random
interleaver, simulations are carried out in MATLAB®. Results show that our proposed
seed based random interleaver has near optimal properties of ‘spread’ and ‘dispersion’.
Furthermore, the proposed interleaver is evaluated in terms of bit error rate (BER) versus
length of burst error in a single carrier system both before and after modulation. The
proposed interleaver out-performs the built in RANDINTLV in MATLAB® when used in
the same system. It shows that proposed interleaver can convert greater amount of burst
errors into simple random errors than that of MATLAB® interleaver. The proposed
interleaver is also tested in IEEE 802.16e based WiMAX system with Stanford University Interim (SUI) channels to compare the performance of average BER versus
SNR for both pre modulation and post modulation interleaver. Results show that pre
modulation interleaver and post modulation has same performance.
There is also a side advantage of this seed based interleaver, in that it generates a variety
of unique random-looking interleaving sequences. Only a receiver that has the knowledge
of the input seed can generate this sequence and no one else. If the interleaving patterns
are kept secure then it can possibly be used to introduce an extra layer of security at
physical (PHY) layer. In that way, at PHY layer, one builds an additional entry barrier to
break through and it comes with no extra cost. This property has been investigated by
carrying out key sensitivity analysis to show that the attacks to guess key can be very
futile, as difference at 4th decimal place in the initial condition can lead to entirely
different scrambling
A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications
Wireless channels are characterized by multipath and fading that can often cause long
burst of errors. Even though, to date, many very sophisticated error correcting codes have
been designed, yet none can handle long burst of errors efficiently. An interleaver, a
device that distributes a burst of errors, possibly caused by a deep fade, and makes them
appear as simple random errors, therefore, proves to a very useful technique when used in
conjunction with an efficient error correcting code.
In this work, a novel near optimal seed based random interleaver is designed. An optimal
interleaver scatters a given burst of errors uniformly over a fixed block of data - a
property that is measured by so called ‘spread’. The design makes use of a unique seed
based pseudo-random sequence generator or logistic map based chaotic sequence
generator to scramble the given block of data. Since the proposed design is based on a
seed based scrambler, the nature of input is irrelevant. Therefore, the proposed interleaver
can interleave either the bits or the symbols or the packets or even the frames.
Accordingly, in this work, we analyze the suitability of interleaver when introduced
before or after the modulation in single carrier communication systems and show that
interleaving the bits before modulation or interleaving the symbols after modulation has
same advantage. We further show that, in an orthogonal frequency division multiplexing
(OFDM) systems, the position of interleaver, whether before or after constellation
mapper, has no significance, and is interchangeable. However, scrambling symbols is
computationally less expensive than scrambling bits.
For the purpose of analyzing the performance of the proposed seed based random
interleaver, simulations are carried out in MATLAB®. Results show that our proposed
seed based random interleaver has near optimal properties of ‘spread’ and ‘dispersion’.
Furthermore, the proposed interleaver is evaluated in terms of bit error rate (BER) versus
length of burst error in a single carrier system both before and after modulation. The
proposed interleaver out-performs the built in RANDINTLV in MATLAB® when used in
the same system. It shows that proposed interleaver can convert greater amount of burst
errors into simple random errors than that of MATLAB® interleaver. The proposed
interleaver is also tested in IEEE 802.16e based WiMAX system with Stanford University Interim (SUI) channels to compare the performance of average BER versus
SNR for both pre modulation and post modulation interleaver. Results show that pre
modulation interleaver and post modulation has same performance.
There is also a side advantage of this seed based interleaver, in that it generates a variety
of unique random-looking interleaving sequences. Only a receiver that has the knowledge
of the input seed can generate this sequence and no one else. If the interleaving patterns
are kept secure then it can possibly be used to introduce an extra layer of security at
physical (PHY) layer. In that way, at PHY layer, one builds an additional entry barrier to
break through and it comes with no extra cost. This property has been investigated by
carrying out key sensitivity analysis to show that the attacks to guess key can be very
futile, as difference at 4th decimal place in the initial condition can lead to entirely
different scrambling
A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications
Wireless channels are characterized by multipath and fading that can often cause long
burst of errors. Even though, to date, many very sophisticated error correcting codes have
been designed, yet none can handle long burst of errors efficiently. An interleaver, a
device that distributes a burst of errors, possibly caused by a deep fade, and makes them
appear as simple random errors, therefore, proves to a very useful technique when used in
conjunction with an efficient error correcting code.
In this work, a novel near optimal seed based random interleaver is designed. An optimal
interleaver scatters a given burst of errors uniformly over a fixed block of data - a
property that is measured by so called 'spread'. The design makes use of a unique seed
based pseudo-random sequence generator or logistic map based chaotic sequence
generator to scramble the given block of data. Since the proposed design is based on a
seed based scrambler, the nature of input is irrelevant. Therefore, the proposed interleaver
can interleave either the bits or the symbols or the packets or even the frames.
Accordingly, in this work, we analyze the suitability of interleaver when introduced
before or after the modulation in single carrier communication systems and show that
interleaving the bits before modulation or interleaving the symbols after modulation has
same advantage. We further show that, in an orthogonal frequency division multiplexing
(OFDM) systems, the position of interleaver, whether before or after constellation
mapper, has no significance, and is interchangeable. However, scrambling symbols is
computationally less expensive than scrambling bits.
For the purpose of analyzing the performance of the proposed seed based random
interleaver, simulations are carried out in MA TLAB®. Results show that our proposed
seed based random interleaver has near optimal properties of 'spread' and 'dispersion'.
Furthermore, the proposed interleaver is evaluated in terms of bit error rate (BER) versus
length of burst error in a single carrier system both before and after modulation. The
proposed interleaver out-performs the built in RANDINTLV in MA TLAB® when used in
the same system. It shows that proposed inter Ieaver can convert greater amount of burst
errors into simple random errors than that of MA TLAB® interleaver. The proposed
interleaver is also tested in IEEE 802.16e based WiMAX system with Stanford University Interim (SUI) channels to compare the performance of average BER versus
SNR for both pre modulation and post modulation interleaver. Results show that pre
modulation interleaver and post modulation has same performance.
There is also a side advantage of this seed based interleaver, in that it generates a variety
of unique random-looking interleaving sequences. Only a receiver that has the knowledge
of the input seed can generate this sequence and no one else. If the interleaving patterns
are kept secure then it can possibly be used to introduce an extra layer of security at
physical (PHY) layer. In that way, at PHY layer, one builds an additional entry barrier to
break through and it comes with no extra cost. This property has been investigated by
carrying out key sensitivity analysis to show that the attacks to guess key can be very
futile, as difference at 41
h decimal place in the initial condition can lead to entirely
different scrambling
Dynamic block encryption with self-authenticating key exchange
One of the greatest challenges facing cryptographers is the mechanism used
for key exchange. When secret data is transmitted, the chances are that there
may be an attacker who will try to intercept and decrypt the message. Having
done so, he/she might just gain advantage over the information obtained, or
attempt to tamper with the message, and thus, misguiding the recipient.
Both cases are equally fatal and may cause great harm as a consequence.
In cryptography, there are two commonly used methods of exchanging secret
keys between parties. In the first method, symmetric cryptography, the key is
sent in advance, over some secure channel, which only the intended recipient
can read. The second method of key sharing is by using a public key exchange
method, where each party has a private and public key, a public key is shared
and a private key is kept locally. In both cases, keys are exchanged between
two parties.
In this thesis, we propose a method whereby the risk of exchanging keys
is minimised. The key is embedded in the encrypted text using a process
that we call `chirp coding', and recovered by the recipient using a process
that is based on correlation. The `chirp coding parameters' are exchanged
between users by employing a USB flash memory retained by each user. If the
keys are compromised they are still not usable because an attacker can only
have access to part of the key. Alternatively, the software can be configured
to operate in a one time parameter mode, in this mode, the parameters
are agreed upon in advance. There is no parameter exchange during file
transmission, except, of course, the key embedded in ciphertext.
The thesis also introduces a method of encryption which utilises dynamic blocks, where the block size is different for each block. Prime numbers are
used to drive two random number generators: a Linear Congruential Generator
(LCG) which takes in the seed and initialises the system and a Blum-Blum
Shum (BBS) generator which is used to generate random streams to encrypt
messages, images or video clips for example. In each case, the key created is
text dependent and therefore will change as each message is sent.
The scheme presented in this research is composed of five basic modules. The
first module is the key generation module, where the key to be generated is
message dependent. The second module, encryption module, performs data
encryption. The third module, key exchange module, embeds the key into
the encrypted text. Once this is done, the message is transmitted and the
recipient uses the key extraction module to retrieve the key and finally the
decryption module is executed to decrypt the message and authenticate it.
In addition, the message may be compressed before encryption and decompressed
by the recipient after decryption using standard compression tools
Implementation of a Symmetric Chaotic Encryption Scheme
Voice over Internet Protocol technology (VoIP) is progressing commendably, but packet
loss, propagation delay, jitter, unreliable IP networks, and vulnerability to attacks by
Internet hackers are among critical issues that have been identified. Voice privacy and
security needs to focused upon and data encryption techniques are the answers in
providing the security needed. However, traditional cryptosystems demand high
computational complexity andhigh digital signal processors which in return increases the
cost of implementation.
There is parallel growth in cryptographic techniques which originated anintense research
activity and the search for new directions in cryptography such as chaotic encryption.
Due to its deterministic nature and its sensitivity to initial conditions, chaos has a certain
potential in creating a newway of securing information to be transmitted or stored.
There are two main objectives to this project. First is study the feasibility of the chaotic
encryption scheme in providing a solution in to preserve data security while maintaining
the voice quality for voice over Internet Protocol. Secondly, a new scheme based on a
chaos system will be implemented for voice data. In order to achieve the second
objective, a study had been carried out on other proposed schemes mainly the
Hierarchical Data Security Protection (HDSP) for VoIP. This scheme performs two main
operations which is the data-frame interleaving and intra-frame data encryption using bit
swapping. Based onthe HDSP scheme, the author suggests a new scheme using two level
encryption techniques, based on chaos. In this scheme, the author uses the bit swapping
technique as the second encryption-decryption level and enhances it with a first level
encryption-decryption scheme using the two's compliment overflow nonlinearity
encoder-decoder pair.
The implementation ofthis scheme is specified to do real time processing ofvoice data. It
can also be used to read, encrypt and write a wave file. The entire system is implemented,
tested and validated using MATLAB and Visual C++.
Due to the promising prospect ofchaotic encryption in the field ofcryptography, and the
lack ofimplementation ofthis new encryption-decryption algorithm, this project focuses
on introducing a new symmetric encryption-decryption scheme based on a chaos system
for VoIP
Applications of Artificial Intelligence to Cryptography
This paper considers some recent advances in the field of Cryptography using Artificial Intelligence (AI). It specifically considers the applications of Machine Learning (ML) and Evolutionary Computing (EC) to analyze and encrypt data. A short overview is given on Artificial Neural Networks (ANNs) and the principles of Deep Learning using Deep ANNs. In this context, the paper considers: (i) the implementation of EC and ANNs for generating unique and unclonable ciphers; (ii) ML strategies for detecting the genuine randomness (or otherwise) of finite binary strings for applications in Cryptanalysis. The aim of the paper is to provide an overview on how AI can be applied for encrypting data and undertaking cryptanalysis of such data and other data types in order to assess the cryptographic strength of an encryption algorithm, e.g. to detect patterns of intercepted data streams that are signatures of encrypted data. This includes some of the authors’ prior contributions to the field which is referenced throughout. Applications are presented which include the authentication of high-value documents such as bank notes with a smartphone. This involves using the antenna of a smartphone to read (in the near field) a flexible radio frequency tag that couples to an integrated circuit with a non-programmable coprocessor. The coprocessor retains ultra-strong encrypted information generated using EC that can be decrypted on-line, thereby validating the authenticity of the document through the Internet of Things with a smartphone. The application of optical authentication methods using a smartphone and optical ciphers is also briefly explored
Multi-algorithmic Cryptography using Deterministic Chaos with Applications to Mobile Communications
In this extended paper, we present an overview of the principal issues associated with cryptography, providing historically significant examples for illustrative purposes as part of a short tutorial for readers that are not familiar with the subject matter. This is used to introduce the role that nonlinear dynamics and chaos play in the design of encryption engines which utilize different types of Iteration Function Systems (IFS). The design of such encryption engines requires that they conform to the principles associated with diffusion and confusion for generating ciphers that are of a maximum entropy type. For this reason, the role of confusion and diffusion in cryptography is discussed giving a design guide to the construction of ciphers that are based on the use of IFS. We then present the background and operating framework associated with a new product - CrypsticTM - which is based on the application of multi-algorithmic IFS to design encryption engines mounted on a USB memory stick using both disinformation and obfuscation to ‘hide’ a forensically inert application. The protocols and procedures associated with the use of this product are also briefly discussed
Digital watermarking and novel security devices
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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