PN sequences

With the fast progress of electronic data exchange, information security was become more important in data storage and transmission. And because of widely use of images in industrial process, it is important to protect the confidential image data from unauthorized access. In this paper, a proposed seed was generate as a key to a Linear Feed Back Shift Register (LFBSR) which applied on the RGB color image (Bmp image) with random keys=2 100. The performance of this algorithm has been implemented on two types of Bmp image, the 8-bit Bmp image (palletized image) and 24-bit Bmp image.

This paper presents three new sets of frequency hopping sequences, which are converted into sequences for CDMA. One of the CDMA sequence families is optimal with respect to the Welch bound, and two are nearly optimal. Our sequences are available for more lengths, and have much higher linear complexity than other CDMA sequences. They have a similar structure to the small Kasami set, but are balanced. The CDMA sequences are constructed using a composition method, which combines new shift sequences with pseudonoise columns to form an array. The array dimensions are relatively prime, so it is unfolded using the Chinese Remainder Theorem. Each of our constructions gives rise to two additional families with larger family sizes but worse correlation as explained in Section 4.2.

We introduce a construction for periodic zero correlation zone (ZCZ) sequences over roots of unity. The sequences share similarities to the perfect periodic sequence constructions of Liu, Frank, and Milewski. The sequences have two non-zero off-peak autocorrelation values which asymptotically approach ±2π, so the sequences are asymptotically perfect.

Linear complexity is an important parameter for arrays that are used in applications related to information security. In this work we survey constructions of two and three dimensional arrays, and present new results on the multidimensional linear complexity of periodic arrays obtained using the definition and method proposed in [2, 7, 12]. The results include a generalization of a bound for the linear complexity, a comparison with the measure of complexity for multisequences, and computations of the complexity of arrays with periods that are not relatively prime for which the "unfolding method" does not work. Conjectures for exact formulas and the asymptotic behavior of the complexity of some array constructions are formulated. We also present open source software for constructing multidimensional arrays and for computing their multidimensional linear complexity.

In this work we present two generators for the group of symmetries of the generic (m + 1) dimensional periodic Costas arrays over elementary abelian (Zp) m groups: one that is defined by multiplication on m dimensions and the other by shear (addition) on m dimensions. Through exhaustive search we observe that these two generators characterize the group of symmetries for the examples we were able to compute. Following the results, we conjecture that these generators characterize the group of symmetries of the generic (m + 1) dimensional periodic Costas arrays over elementary abelian (Zp) m groups.

This paper describes the synthesis of matrices with good correlation, from cyclic shifts of pseudonoise columns. Optimum matrices result whenever the shift sequence satisfies the constant difference property. Known shift sequences with the constant (or almost constant) difference property are: Quadratic (Polynomial) and Reciprocal Shift modulo prime, Exponential Shift, Legendre Shift, Zech Logarithm Shift, and the shift sequences of some m-arrays. We use these shift sequences to produce arrays for watermarking of digital images. Matrices can also be unfolded into long sequences by diagonal unfolding (with no deterioration in correlation) or row-by-row unfolding, with some degradation in correlation.

This paper generalizes three constructions of families of sequences with bounded off peak correlation with application to Code Division Multiple Access (CDMA), frequency hopping, and Ultra Wide Band (UWB). These new families present flexible family sizes and sequence lengths, making them well suited to wireless communications and Multiple Input Multiple Output (MIMO) radar. In particular, we show that the generalized Kamaletdinov I construction offers the lowest off-peak correlation for a given family size. For the two smallest family sizes, this construction asymptotically matches the performance of the small Kasami set and Gold codes, respectively. Among other properties, it has one of the slowest off-peak correlation growth of all known constructions, increasing proportionally to the logarithm of the family size and generates frequency and time hopping sequences.

This chapter presents an adaptive Multicarrier Frequency Hopping Spread Spectrum (MCFH-SS) system employing proposed Quasi Cyclic Low Density Parity Check (QC-LDPC) codes instead of the conventional LDPC codes. A new technique for constructing the QC-LDPC codes based on row division method is proposed. The new codes offer more flexibility in terms of girth, code rates and codeword length. Moreover, a new scheme for channel prediction in MCFH-SS system is also proposed. The technique adaptively estimates the channel conditions and eliminates the need for the system to transmit a request message prior to transmitting the packet data. The proposed adaptive MCFH-SS system uses PN sequences to spread out frequency spectrum, reduce the power spectral density and minimize the jammer effects.

Frequency hopping (FH) is a spread spectrum transmission technique that achieves frequency diversity gain over frequency selective fading channels and also has a low probability of interception. This technique has been widely used in military applications, for its recognized antijamming performance, and in some wireless standards such as GSM and Bluetooth, for its interference resistance. In this paper we present a fully digital architecture for performing frequency hopped modulation. The proposed structure is composed of a cascade of two polyphase up converter channelizers. The first one performs the M-FSK modulation of the baseband signals while the second one accomplishes the task of hopping the FSK modulated spectra under the control of a pseudorandom sequence generator. According to the authors' knowledge, a fully digital architecture for frequency hopped transmission has never been presented in the literature until now. In this paper, both theoretical aspects and simulatio...

The recent explosion in multimedia and networking application places a great demand on efficient transmission of images at low bit rate with high security. Mixing several existing standard encryption techniques with image encoding tends to change the compression ratio greatly. In this paper, a novel image encryption algorithm is embedded as a part of JPEG image encoding scheme to meet three major necessities: 1) To provide temporal security against casual observer 2) To preserve the compression ratio 3) Remain compliant with the JPEG file format. In the proposed algorithm, the modified DCT blocks are confused by a fuzzy PN sequence. In addition to that, the DCT coefficients of each modified DCT block are converted to unique uncorrelated symbols, which are confused by another fuzzy PN sequence. Finally, the variable length encoded bits are encrypted by chaotic stream cipher. An amalgamation of all the three techniques with random combination of seeds will provide the required security against the casual listener/observer where the security needed is only in-terms of few hours.

Multimedia is one of the most popular data shared in the Web, and the protection of it via encryption techniques is of vast interest. In this paper, a secure and computationally feasible Algorithm called Optimized Multiple Huffman Tables (OMHT) technique is proposed. OMHT depends on using statistical-model-based compression method to generate different tables from the same data type of images or videos to be encrypted leading to increase compression efficiency and security of the used tables. A systematic study on how to strategically integrate different atomic operations to build a multimedia encryption system is presented. The resulting system can provide superior performance over other techniques by both its generic encryption and its simple adaptation to multimedia in terms of a joint consideration of security, and bitrate overhead. The effectiveness and robustness of this scheme is verified by measuring its security strength and comparing its computational cost against other techniques. The proposed technique guarantees security, and fastness without noticeable increase in encoded image size.

The authors propose a framework to encrypt Baseline JPEG files directly at bitstream level, i.e., without the need to recompress them. The authors’ approach enables encrypting more than 25 pictures per second in VGA resolution, allowing real-time operation in typical video surveillance applications. In addition, their approach preserves the length of the bitstream while being completely format-compliant. Furthermore, the authors show that an attack on the encryption process, which partly relies on AES, is practically infeasible.

Based on two methods recently proposed-the 'Ranging Criterion' (RC) and the 'Generators Ranging Criterion' (GRC)-new (quasi-orthogonal) even BCH-derived sequences are generated which are very attractive for synchronous or quasi-synchronous Code Division Multiple-Access (CDMA) systems. Numerical results show that the new family of BCH-derived sequences can contain a higher number of quasi-orthogonal sequences with lower correlation values and higher processing gains (PGs) than the spreading sequences typically used in the third generation of mobile communications system, UMTS or in the recent large area synchronised CDMA (LAS-CDMA) technology. It is shown that the even BCHderived sequences are easily generated by a linear shift register generator, allowing the construction of systems with receiver structures of low complexity as compared with those of quasi-synchronous systems using low correlation zone sequences, as for instance the LAS-CDMA system.

This paper focuses on Spread Spectrum technique and its interference mitigation feature as applied in wireless communication. With spread spectrum technology it is possible to implement the transmission of multiple signals over wider ranges of spectrum without resulting to interference from other signals transmitted over the same frequencies. It does this by rejecting any received signal that does not carry the proper code. Interference rejection, one of the several features of spread spectrum technology is a difficult concept to understand. It is therefore proper to x-ray this topic in a less complex manner so that it can be well understood by those who are not mathematically grounded. In view of this a further simplified approach in presenting this subject is necessary. A tutorial approach is used to simplify this subject for better understanding and how this feature is used in Code Division Multiple Access (CDMA) systems. To show how multipath interference rejection is achieved in CDMA systems simple equations and schematics were used. The discussions cover the method of code recognition at the receiver which serves as a technique for interference mitigation. The paper helps to understand the theory of code recognition in Spread Spectrum, and thus provides answer to the question on how does interference mitigation or rejection in spread spectrum works?

The need for protecting a huge amount of digital images on the internet has become an important requirement against different kind of attacks in order to insure transmitted process in a secure way. Cryptography introduces many security goals to achieve privacy of image include confidentiality, authentication and integrity. Encryption process may applied on the result of JPEG DCT-based encoding process, which are DC and AC coefficients, where DC coefficients present the average of the overall magnitude of the input image and AC coefficients present the higher frequency components of image. In this paper, we develop a new model for securing the transmitted images via wireless network by parsing JPEG bitstream to encrypting both DC and AC coefficients in each 8 × 8 block of image. This work utilizes the features of DCT-based encoding process preserving low complexity, efficient compression, and robustness to protect the image integrity. The experiments result shows that the proposed approach gives an interesting and a significant robustness ratio reaching a range of 60.3 dB for Peak Signal-to-Noise Ratio (PSNR) and a 0.006% for Bit Error Rate (BER) in average. The obtained results are discussed in details. c

Families of sequences with low off-peak autocorrelation and low crosscorrelation are highly valued in spread-spectrum communication. Digital watermarking has an equal need for diverse families of orthogonal multi-dimensional (nD) arrays, where each array has optimal correlation properties. In this reported work, a 1D discrete projection method is used to construct new families of nD orthogonal arrays of size p n , with p a 4k − 1 prime. Finite field algebra and Hadamard matrices are applied to analyse these arrays. The periodic autocorrelation of each array is 'perfect' (p 2 − 1 peak value, with −1 off-peak for p × p arrays). The cross-correlation between any pair of the p members of each 2D family has the lowest possible values, 0 or ±p. The arrays can be synthesised for arbitrarily large p and outperform Kasami sequences. The alphabet values for these optimal arrays can be roots of unity or signed integers. The aperiodic autocorrelation of the p × p arrays can attain a merit factor of above 3 at shift (p/4, p/4), consistent with Golay's conjecture in 1D.

Multimedia is one of the most popular data shared in the Web, and the protection of it via encryption techniques is of vast interest. In this paper, a secure and computationally feasible Algorithm called Optimized Multiple Huffman Tables (OMHT) technique is proposed. OMHT depends on using statistical-model-based compression method to generate different tables from the same data type of images or videos to be encrypted leading to increase compression efficiency and security of the used tables. A systematic study on how to strategically integrate different atomic operations to build a multimedia encryption system is presented. The resulting system can provide superior performance over other techniques by both its generic encryption and its simple adaptation to multimedia in terms of a joint consideration of security, and bitrate overhead. The effectiveness and robustness of this scheme is verified by measuring its security strength and comparing its computational cost against other techniques. The proposed technique guarantees security, and fastness without noticeable increase in encoded image size.

Based on two methods recently proposed-the 'Ranging Criterion' (RC) and the 'Generators Ranging Criterion' (GRC)-new (quasi-orthogonal) even BCH-derived sequences are generated which are very attractive for synchronous or quasi-synchronous Code Division Multiple-Access (CDMA) systems. Numerical results show that the new family of BCH-derived sequences can contain a higher number of quasi-orthogonal sequences with lower correlation values and higher processing gains (PGs) than the spreading sequences typically used in the third generation of mobile communications system, UMTS or in the recent large area synchronised CDMA (LAS-CDMA) technology. It is shown that the even BCHderived sequences are easily generated by a linear shift register generator, allowing the construction of systems with receiver structures of low complexity as compared with those of quasi-synchronous systems using low correlation zone sequences, as for instance the LAS-CDMA system.

In the satellite telemetry command, controlling the power of the uplink signal, radiated away from the Earth to the spacecraft and downlink signal, radiated toward the Earth form the spacecraft is very important. The Uplink is transmitted at high power because of the unlimited power, while downlink should be controlled in power because of limited spacecraft power resources. This results in a lower Power Spectral Density (PSD) for the downlink and higher PSD for the uplink, which in many cases the uplink power due to be strong enough to reach the satellites at GEO would often also violate the PSD limits in the other orbits satellite telemetry signals like LEO. In addition due to long distance between the Earth and satellite, the received signals at the both terrestrial and transponder receivers are extremely week and strongly influenced by intentional interference (like jamming) or inadvertent interferences (such as the ASI). Spreading spectrum can solve the PSD problems for both directions but consumes a wide bandwidth. Fortunately, signals can be distinguished by using different spreading codes, allowing for CDMA. The Pseudo Noise (PN) spreading codes allow using many satellites or users (located in one satellite) the same frequency with overlapping signals simultaneously and also range measurement as useful ability to track the spacecraft in the space by the expanding value of the PN codes (Doppler Shift).[1] This paper specially considers to satellite telemetry data transmission immunity from the interference using Direct Sequence Spread Spectrum (DSSS) based on CDMA namely DS-CDMA (Direct Sequence-CDMA) by the unique properties correlation functions of the Gold and M-Sequence codes. Also the codes are examined in the fading channels, Reyleigh and AWGN, in terms of the BER vs. Eb/No to compare the practical results with theoretical values.

This paper generalizes three constructions of families of sequences with bounded off peak correlation with application to Code Division Multiple Access (CDMA), frequency hopping, and Ultra Wide Band (UWB). These new families present flexible family sizes and sequence lengths, making them well suited to wireless communications and Multiple Input Multiple Output (MIMO) radar. In particular, we show that the generalized Kamaletdinov I construction offers the lowest off-peak correlation for a given family size. For the two smallest family sizes, this construction asymptotically matches the performance of the small Kasami set and Gold codes, respectively. Among other properties, it has one of the slowest off-peak correlation growth of all known constructions, increasing proportionally to the logarithm of the family size and generates frequency and time hopping sequences.

In this paper, we have implemented Radar Transmitter-Receiver. Direct Sequence Spread Spectrum BPSK is chosen as modulation method because of its numerous advantages like accuracy of ranging, sensitivity, targetseparation, accuracy of power-estimation, interference suppression, etc. We have employed this scheme using MATLAB Simulink which is a software package for modelling, simulating, and analysing dynamic systems at any point.

— Based on two recently proposed methods in the literature − the “Ranging Criterion ” and the “Generators Ranging Criterion ” − new (quasi-orthogonal) even BCH-derived sequences are generated, which are very attractive for (synchronous or quasi-synchronous) CDMA applications. These sequences can be easily generated by a linear shift register generator, adding one extra zero or by a cyclically read memory table. Simulation results showed that the new family of even BCH-derived sequences can contain a higher number of sequences with lower correlation values and higher processing gains than the spreading sequences typically used in the third generation of mobile communications system, UMTS.

The easiness of data-flow in digital media, seriously claims the ownership of intellectual material. To solve this problem, researchers have worked on different watermarking methods to embed ownership data into original signals. Unfortunately, none of the available techniques have been able to assure an acceptable level of security. Though, recently some senior members of the image processing community are expressing essential doubt about the appropriateness of watermarking for data protection and declare it more as a nonsecure tool for data embedding. In this paper, we propose a fast method for copy protection of color visual objects. The proposed method, deliberately embeds fake edges and color alterations into a given a color image in the way that it carries the content of the original image. Using this damaged image prevents the unauthorized users to pirate the demo version of images and video placed at homepages to help consumers select the images they wish to purchase. The main contribution of the proposed method is that there is a small key for the distorted image that reverts all degradations in a lossless manner. To the knowledge of the authors, this is the first time this kind of copy protection is addressed. While there are literally infinite ways to encrypt a given image, it is proved both experimentally and mathematically that there is no practical chance to crack the code.

This paper presents new constructions of families of binary and ternary arrays with low off-peak (periodic) autocorrelation and low cross-correlation for application to video watermarking. The constructions are based on the composition method which uses a shift sequence to cyclically shift a commensurate "column" sequence/array. The shift sequence/array has auto and cross-hit values constrained to 1 or 2, while the column sequence/array is pseudonoise. The shift sequences are new, while the column sequence is a Sidelnikov sequence, and the column array is a multi-dimensional Legendre array. The shift sequence constructions involve mapping the elements of a finite field onto its associated multiplicative group, the field plus infinity and other such variations. The constructions yield families of arrays suitable for embedding into video as watermarks. Examples of such watermarks are presented. The watermarks survive H264 compression, and are being considered for a video security standard.

In a DS-SS system, each user is assigned a unique code sequence (PN-Sequence) that allows the user to spread the information signal across the assigned frequency band. Signals from the various users are separated at the receiver by cross correlation of the received signal with each of the possible user code sequences. Possible narrow band interference is also suppressed in this process. Because of its advantages, it is used in CDMA systems to assign a unique code to every user. This paper describes the design of CDMA modem in FPGA based on DSSS. 8051 microcontroller & FPGA were linked with rf transmitter/receiver, a acknowledgement was being sent to FPGA once the bit was transmitted/receive by the 8051 microcontroller. At the receiver output of 8051 microcontroller was compared with the threshold levels using a comparator and this provides binary output which is the actually transmitted sequence.

This paper presents new constructions of families of binary and ternary arrays with low off-peak (periodic) autocorrelation and low cross-correlation for application to video watermarking. The constructions are based on the composition method which uses a shift sequence to cyclically shift a commensurate "column" sequence/array. The shift sequence/array has auto and cross-hit values constrained to 1 or 2, while the column sequence/array is pseudonoise. The shift sequences are new, while the column sequence is a Sidelnikov sequence, and the column array is a multi-dimensional Legendre array. The shift sequence constructions involve mapping the elements of a finite field onto its associated multiplicative group, the field plus infinity and other such variations. The constructions yield families of arrays suitable for embedding into video as watermarks. Examples of such watermarks are presented. The watermarks survive H264 compression, and are being considered for a video security standard.

Families of sequences with low periodic off peak autocorrelation and low periodic crosscorrelation are important in wireless communications, radar, sonar and audio watermarking. Families of such two and three-dimensional arrays find applications in image and video watermarking respectively. Classical optimal sequence family constructions such as Gold codes and the small and large Kasami sets and their variations such as No-Kumar and interleaved sequences are based on m sequences which are generated by linear feedback shift registers. This is the most compact and fastest method of generating such sequences. A disadvantage is that because of their low linear complexity they are not secure. More recent optimal constructions, such as those found by Kamaletdinov, Moreno and Tirkel and generalized by the method of composition and substitution can have high complexity and consequently be secure. However, this makes the generation of such sequences memory intensive and slow. This also applies to arrays generated by this method. In this paper, we present a cascade linear feedback shift register implementation of such sequences, which is the most compact in terms of memory, and the fastest possible. This permits an efficient generation of sequences and arrays in real time in FPGAs. Such an implementation requires minimal memory usage and permits dynamic updating of sequences or arrays. The aim of our work was to broaden current knowledge of sets of sequences with low correlation by studying their implementation using linear feedback shift registers. A remarkable feature of these families is their similarities in terms of implementation and it may open new ways to characterize sequences with low correlation, making it easier to generate them. It also validates some conjectures made by Moreno and Tirkel about arrays constructed using the method of composition and substitution.

This paper proposes and investigates a spread spectrum (SS) system which can realize both ranging and communication between a vehicle and a roadside. In order to improve performance of ranging and communication, we propose schemes of cancelling mutual interference between a SS ranging signal and SS communication one. Computer simulations illustrate improved performance of both ranging accuracy and data bit error rate.

This paper presents a new method, of recompressing a JPEG crypto-compressed image. In this project, we propose a cryptocompression method which allows recompression without any information about the encryption key. The recompression can be executed on the JPEG bitstream directly by removing the last bit of the code representation of a non null DCT coefficient and adapting its Huffman code part. To be able to apply this approach, the quantization table is slightly modified to make up the modifications. This method is efficient to recompress a JPEG cryptocompressed image in terms of ratio compression. Moreover, since the encryption is fully reversible, the decryption of the recompressed image produces an image that has a similar visual quality compared to the original compressed image.

Image encryption in frequency domain has an advantatge of resistance to many image processing operations. This paper presents a robustness analysis of a proposed selective image encryption algorithm based on chaos. The cipher-images was modified by common image processings such as JPEG compression, adding noise, brightness/contrast adjustment, and image resizing. Based on experiment results, the cipher-images were robust to the image processing operations, since the modifications have little influence on low frequency DCT coefficients. The decrypted images can be still recognized well, although they are just like noised.

Salah satu kelebihan utama sistem komunikasi Spread Spectrum adalah kemampuannya mengirimkan data informasi disertai kode-kode unik sehingga hanya perangkat penerima tertentu saya yang mampu mendeteksinya. Sangat banyak metode pembangkitan kode unik pada spread spectrum ini, salah satunya adalah direct sequence. Penerapan metode ini banyak direalisasikan pada teknologi CDMA, dikarenakan kesederhanaan rancangan dan relatif mudah dalam menganalisis karakteristik kerja sistemnya, terutama bagian sebaran kode unik pada sebuah lebar pita transmisi radio. Sumber kode unik dalam penelitian ini berasal dari data acak yang dihasilkan oleh pembangkit derau semu atau pseudo noise generator melalui pengaturan panjang kodenya sebesar 16, dengan tingkat kestabilan frekuensi sistem pembangkit kode unik dan frekuensi pembawa masing-masing sebesar 15,020 kHz dan 499,9419 kHz. Kedua frekuensi ini masing-masing menghasilkan nilai persen kesalahannya sebesar 0,0412 % dan 0,000049 %, sehingga dampaknya masih cukup baik bagi metode ini, apabila diimplementasikan pada teknologi CDMA, khususnya diperuntukan untuk laju kecepatan data rendah.

Pseudo-Random or pseudo-noise and Orthogonal Spreading sequences are widely used in the Wideband Code Division Multiple Access (WCDMA) systems using Rake receiver. This paper shows the practical aspect for direct sequences DSCDMA and also the orthogonal codes are discussed. This paper compares the execution results of the direct sequence spread spectrum-baseband QPSK modulation with various types of short codes: Barker, Hadamard, Kasami, by measuring the BER (Pe) by using autocorrelation and cross correlation functions. The simulation results shows the system using Barker code is the best system with probability of error (Pe) for Barker code is 4.9 ×10 -4 at 10 dB signal-to-noise ratio (SNR)after comparing with other codes.

The rising popularity of social networks and cloud computing has greatly increased number of JPEG compressed image exchanges. In this context, the security of the transmission channel and/or the cloud storage can be susceptible to privacy leaks. Selective encryption is an efficient tool to mask image content and to protect confidentiality while remaining formatcompliant. However, image processing in the encrypted domain is not a trivial task. In this work, we present a JPEG cryptocompression method which allows us to recompress a JPEG crypto-compressed image several times, without any information about the secret key or the original image content. Indeed, using the proposed method in this paper, each recompression can be done directly on the JPEG bitstream by removing the last bit of the code representation of each non-zero coefficient, adapting the entropic code part, and slightly modifying the quantization table. This method is efficient to recompress JPEG crypto-compressed images in terms of ratio compression. Moreover, the decryption of the recompressed image produces an image with a very similar visual quality when compared to the original image, according to the obtained results.

The JPEG Images play a significant role in present multimedia based computing industry. Being a popular lossy mode of image compression, The JPEG has extensively been being used in almost all sorts of digital device including the mobile phones, tablet and handheld computers. Although the popularly used Baseline JPEG Algorithm is an easy one to be performed by the powerful processors, sti ll the small devices of less capable processors suffer a lot from encoding or decoding a JPEG image by the Baseline JPEG Algorithm. This is due to some complex computations required by Baseline JPEG. This paper discovers the computational cost currently needed by Baseline JPEG and suggests an efficient way to encode or decode the JPEG images so that the overall computational cost of the Baseline JPEG Algorithm is reduced with less affecting the obtainable Compression Ratio and Peak Signal to Noise Ratio (PSNR). The suggested cost reduction technique has been tested upon some small computing devices ...

Frequency hopping (FH) is a spread spectrum transmission technique that achieves frequency diversity gain over frequency selective fading channels and also has a low probability of interception. This technique has been widely used in military applications, for its recognized antijamming performance, and in some wireless standards such as GSM and Bluetooth, for its interference resistance. In this paper we present a fully digital architecture for performing frequency hopped modulation. The proposed structure is composed of a cascade of two polyphase up converter channelizers. The first one performs the M-FSK modulation of the baseband signals while the second one accomplishes the task of hopping the FSK modulated spectra under the control of a pseudorandom sequence generator. According to the authors' knowledge, a fully digital architecture for frequency hopped transmission has never been presented in the literature until now. In this paper, both theoretical aspects and simulatio...

Single sequences like Legendre have high linear complexity. Known CDMA families of sequences all have low complexities. We present a new method of constructing CDMA sequence sets with the complexity of the Legendre from new frequency hop patterns, and compare them with known sequences. These are the first families whose normalized linear complexities do not asymptote to 0, verified for lengths up to 6x108. The new constructions in array format are also useful in watermarking images. We present a conjecture regarding the recursion polynomials. We also have a method to reverse the process, and from small Kasami/No-Kumar sequences we obtain a new family of 2n doubly periodic (2n+1)x(2n-1) frequency hop patterns with correlation 2.

This thesis work studied on digital image encryption algorithms performed towards JPEG images. With image encryption algorithms, JPEG images can be securely scrambled or encrypted prior to distribution. The intended recipient will be given a decryption key in which only with this key the receiver can received and decrypt the media for viewing. The proposed approach uses a frequency domain combinational framework of coefficients scrambling with Key Scheduling Algorithm based (KSA-based) permutation. This novel algorithm applies coefficients scrambling using Combined-Reverse-and-Normal-Direction (CRND) scanning together with Distorted DC permutation (DDP). This encryption algorithm involved the manipulation of JPEG zigzag scanning table according to 10 different scanning tables which was derived by reversing the existing zigzag scanning directions. With the same compression properties, this encryption algorithm was shown to be able to produce average file size smaller than baseline JP...

Multimedia is one of the most popular data shared in the Web, and the protection of it via encryption techniques is of vast interest. In this paper, a secure and computationally feasible Algorithm called Optimized Multiple Huffman Tables (OMHT) technique is proposed. OMHT depends on using statistical-model-based compression method to generate different tables from the same data type of images or videos to be encrypted leading to increase compression efficiency and security of the used tables. A systematic study on how to strategically integrate different atomic operations to build a multimedia encryption system is presented. The resulting system can provide superior performance over other techniques by both its generic encryption and its simple adaptation to multimedia in terms of a joint consideration of security, and bitrate overhead. The effectiveness and robustness of this scheme is verified by measuring its security strength and comparing its computational cost against other techniques. The proposed technique guarantees security, and fastness without noticeable increase in encoded image size.

This paper focuses on Spread Spectrum technique and its interference mitigation feature as applied in wireless communication. With spread spectrum technology it is possible to implement the transmission of multiple signals over wider ranges of spectrum without resulting to interference from other signals transmitted over the same frequencies. It does this by rejecting any received signal that does not carry the proper code. Interference rejection, one of the several features of spread spectrum technology is a difficult concept to understand. It is therefore proper to x-ray this topic in a less complex manner so that it can be well understood by those who are not mathematically grounded. In view of this a further simplified approach in presenting this subject is necessary. A tutorial approach is used to simplify this subject for better understanding and how this feature is used in Code Division Multiple Access (CDMA) systems. To show how multipath interference rejection is achieved in CDMA systems simple equations and schematics were used. The discussions cover the method of code recognition at the receiver which serves as a technique for interference mitigation. The paper helps to understand the theory of code recognition in Spread Spectrum, and thus provides answer to the question on how does interference mitigation or rejection in spread spectrum works?

This paper focuses on Spread Spectrum technique and its interference mitigation feature as applied in wireless communication. With spread spectrum technology it is possible to implement the transmission of multiple signals over wider ranges of spectrum without resulting to interference from other signals transmitted over the same frequencies. It does this by rejecting any received signal that does not carry the proper code. Interference rejection, one of the several features of spread spectrum technology is a difficult concept to understand. It is therefore proper to x-ray this topic in a less complex manner so that it can be well understood by those who are not mathematically grounded. In view of this a further simplified approach in presenting this subject is necessary. A tutorial approach is used to simplify this subject for better understanding and how this feature is used in Code Division Multiple Access (CDMA) systems. To show how multipath interference rejection is achieved in CDMA systems simple equations and schematics were used. The discussions cover the method of code recognition at the receiver which serves as a technique for interference mitigation. The paper helps to understand the theory of code recognition in Spread Spectrum, and thus provides answer to the question on how does interference mitigation or rejection in spread spectrum works?

This paper focuses on Spread Spectrum technique and its interference mitigation feature as applied in wireless communication. With spread spectrum technology it is possible to implement the transmission of multiple signals over wider ranges of spectrum without resulting to interference from other signals transmitted over the same frequencies. It does this by rejecting any received signal that does not carry the proper code. Interference rejection, one of the several features of spread spectrum technology is a difficult concept to understand. It is therefore proper to x-ray this topic in a less complex manner so that it can be well understood by those who are not mathematically grounded. In view of this a further simplified approach in presenting this subject is necessary. A tutorial approach is used to simplify this subject for better understanding and how this feature is used in Code Division Multiple Access (CDMA) systems. To show how multipath interference rejection is achieved in CDMA systems simple equations and schematics were used. The discussions cover the method of code recognition at the receiver which serves as a technique for interference mitigation. The paper helps to understand the theory of code recognition in Spread Spectrum, and thus provides answer to the question on how does interference mitigation or rejection in spread spectrum works?

This paper presents the code-phase multiplexed direct-sequence spread spectrum signaling system, which employs parallel transmissions of several data streams modulated by different phase shifts of the same pseudo-noise (PN) code. System performance against single tone jammers is analyzed. Theoretical and simulation results are presented to show that the design increases the processing gain without reducing the data rate

Multimedia is one of the most popular data shared in the Web, and the protection of it via encryption techniques is of vast interest. In this paper, a secure and computationally feasible Algorithm called Optimized Multiple Huffman Tables (OMHT) technique is proposed. OMHT depends on using statistical-model-based compression method to generate different tables from the same data type of images or videos to be encrypted leading to increase compression efficiency and security of the used tables. A systematic study on how to strategically integrate different atomic operations to build a multimedia encryption system is presented. The resulting system can provide superior performance over other techniques by both its generic encryption and its simple adaptation to multimedia in terms of a joint consideration of security, and bitrate overhead. The effectiveness and robustness of this scheme is verified by measuring its security strength and comparing its computational cost against other techniques. The proposed technique guarantees security, and fastness without noticeable increase in encoded image size.

In this paper we proposed the Frequency Hopping Code Division Multiple Access (FH/CDMA) Scheme. In order to improve the spreading process of the spread spectrum modulation system, the conventional pseudo-random code has been replaced by chaotic signal owing to its dynamical behaviour. The spreading code generator has been implemented using discrete integrated circuits and components in which output is controlled by a conventional PN code. The proposed circuit has been tested using real time voice signal and has been transmitted as frequency hopping signal with different hopping patterns. A FH/CDMA Transmitter and Receiver based on proposed chaotic signal generator has been experimentally verified. The results of experimental investigation have been presented in the paper. The waveforms obtained at various check nodes have also been presented.