Search

The western part of Tripura in India due to its geographical location and topography, is under constant risk of rainfall-driven flash floods occurring in the Gumti River causing colossal damage to life and properties almost every year. In this view, an analysis of the scour depth around bridge piers for its safety against the scouring is necessary for mitigating such flood hazards. In this study, we have used a modified HEC-RAS programming tool (HEC-RAS version 5.0.7, March 2019) to develop a scour model for evaluating the maximum local scour depth around bridge piers. We have selected three major bridges namely Subash Sethu, Burima bridge and Machmara bridge on the river Gumti and collected various dimensions of the bridge, scour profiles, sediment properties, etc. and also daily discharge data during 1980 to 2010 from Gomati Barrage Subdivision, Udaipur. Our model is calibrated using several empirical scouring models and it was found that the calculated scour depth from the HEC-RAS software is consistent with other models such as CSU, Larras and Ahmed. The dimensionless analysis is also used to determine the correlation among scour depth (ds) and flow depth (y), Froude number (Fr), angle of attack (θ) and contraction ratio (Cr). In the present study, it is found that an increase in the angle of attack by 3˚ results in an increase in the scour depth of 12.06%, 43.75% and 22.27% for 2-span, 3-span and 4-span bridges respectively. This study also found an increase in scour depth with increasing pier diameter. Overall, the HEC-RAS modeling tool works well in predicting scour depth in all three bridges and the estimated results are in line with other empirical models.

Maintaining an adequate balance between security and other performance metrics like memory requirement, throughput and energy requirement in a resource-constrained environment is a major challenge. The National Institute of Standards and Technology (NIST), in its latest lightweight cryptography report, suggested the suitability of symmetric ciphers in constrained devices. In this paper we have performed statistical security analyses of six state-of-the-art stream ciphers, namely Lizard, Fruit, Plantlet, Sprout, Grain v1 and Espresso, with the help of randomness test, structural test, autocorrelation test and avalanche test. We have also carried out the performance analysis of these ciphers in detail after porting the optimized code of the ciphers to a low-cost microcontroller, namely ATmega 328P. The selection of the device is based on its acceptability in the Internet of Things (IoT)-based network. The statistical security, performance metrics and comparative analysis suggest the suitability of the selected ciphers for providing security in constrained environments.

Image encryption has evolved significantly over the years. This paper proposes an image encryption system using Arnold’s cat map transformation and Snow stream cipher. In our proposed scheme, the image is first scrambled using Arnold’s transformation and then the selected scrambled image pixels are XORed with the Snow cipher keystream sequence to produce the cipher image. Performance of the proposed scheme is analyzed based on several statistical properties. We have observed encouraging statistical properties of the cipher image bitstream making our encryption scheme suitable for applications that requires secured transportation of images.

Stream ciphers are increasingly used for lightweight applications like RFID, Bluetooth, and Wi-Fi communications where the length of the plaintext is initially unknown. Generally, the stream ciphers are characterized by fast encryption and decryption speed. The LFSR-based stream cipher can generate pseudorandom binary strings with good cryptographic properties. Hardware implementation cost is also minimum for it. In this paper, we have discussed the architecture and properties of the LFSR. We have also discussed the properties of secured Boolean function as one of the important components of stream cipher. Here, we have implemented a generalized nonlinear combination of generator-based model comprising LFSR/NLFSR and Boolean function for designing a pRNG. The bitstream properties of pRNG are tabulated and compared with their best attainable parameters.

Dual cover steganography is an evolving technique in the field of covert data transmission. This paper focuses on the concept of using a theoretical single stranded DNA (ssDNA) as a primary cover, which is extracted from an inconspicuous cover image. We have analyzed the security loopholes and performance issues of the existing algorithm and proposed an improved algorithm on the same basis. Performance of both the algorithms are tested against several visual and statistical attacks, and parameterized in terms of both security and capacity. The comparison shows that the proposed improvements provide better overall security.

In this study, trend analysis is done for the meteorological variables such as minimum temperature (Tmin), maximum temperature (Tmax), precipitation (P) and potential evapotranspiration (PET) in and around of the Barak River Basin in India. A total of ten number of meteorological stations with hundred years of observed data are considered for trend analysis. Two non-parametric methods, Mann-Kendall (MK) test and Sen's Slope (SS) estimator, are applied for detection of direction and magnitude of the trend. From the trend analysis, it is found that both the annual as well as seasonal temperature (Tmax and Tmin) are increasing since a couple of decades. Also, it is observed that the average rate of increase in temperature is more in Tmin as compared to Tmax. The decreasing trend of annual and seasonal precipitation pattern is found where negative trends are significant in the monsoon P series with a confidence interval of 95%. The potential evapotranspiration showed increasing trend significantly in monsoon season. Change point analysis is also done to know the shift of trend of meteorological variables. This study gives a fair idea about the variation of meteorological parameters which may be used for climate change analysis as well as sustainable watershed management.

Now-a-days Wireless Mesh Network (WMN) has come up as a widely used technology because of its robustness and cost effectiveness. But it also has some challenges which need to be addressed. Fair packet scheduling is one of the challenging issues as it affects the quality of service (QoS) offered by the WMN to its users. For measurement of fairness, delay is an appealing parameter as the delay suffered by the users of the WMN should be fair enough to get a fair treatment from the network. In this paper, a new fairness index has been computed considering total delay experienced by the packets. For calculating total delay both queuing delay and MAC delay have been considered. Finally, a comparative study have been carried out among different standards of IEEE 802.11s to study the fairness that they offer.

The decision regarding widely acceptable stream cipher for hardware security is one of the challenging assignment. Trivium cipher is ironed out most of the weakness of the other stream ciphers. Beside this, our paper presents the security analysis of Trivium and some modification of cipher which gives better security level. Our primary focus is finding some particular biases of output and reasonable algebraic attack with some guessing approach. More specifically, we show some modifications which can increase its security level without changing its internal structure. For this cipher finally we obtain some new cryptanalytic result and the next part of the paper we study some algebraic analysis of Trivium cipher and we try to show that it is vulnerable to different types of attacks and try to recover the overall internal state of the stream cipher.