Replay attack and password attacks are serious issues in the Kerberos authentication protocol. Many ideas have been proposed to prevent these attacks but they increase complexity of the total Kerberos environment. In this paper we present an improved method which prevents replay attacks and password attacks by using Triple password scheme. Three passwords are stored on Authentication Server and Authentication Server sends two passwords to Ticket Granting Server (one for Application Server) by encrypting with the secret key shared between Authentication server and Ticket Granting server. Similarly, Ticket Granting Server sends one password to Application Server by encrypting with the secret key shared between TGS and application server. Meanwhile, Service-Granting-Ticket is transferred to users by encrypting it with the password that TGS just received from AS. It helps to prevent Replay attack.
An area of about 329 million hectares comprising the entire Indian territory has been studied using Landsat Multispectral Scanner (MSS) false colour composite (FCC) diapositives of 1 : 1 million scale. Different wasteland categories such as salt-affected land, gullied or ravined land, water-logged or marshy land, undulating upland with or without scrub, jhum or forest blank, sandy areas (coastal or desert), barren hill ridge or rock outcrops and snow-covered or glacial areas have been identified and delineated with the aid of monoscopic visual interpretation techniques on an experimental basis. The interpretation technique was supported by intensive ground data and previous geographical knowledge of the area. The area under wastelands in India has been estimated to be of the order of 53.3 million hectares (i.e., 16.2 per cent of the total geographical area of the country). An accuracy of 80 to 90 per cent has been achieved in the identification and mapping of wastelands when compared with the ground surveys. Based on this study, a detailed wasteland mapping project in 146 districts (the districts having 15 per cent or more of wastelands) has been conceived at the insistence of the National Wastelands Development Board at 1:50000 scale using Landsat Thematic Mapper (TM) FCC prints made from bands 2, 3 and 4. A suitable wasteland classification system adoptable for remote sensing techniques has also been developed in India. Furthermore a detailed wastelands image interpretation key using remotely-sensed Landsat TM data has also been developed and is presented in this paper.
The operational capability of optical sensors are limited under cloud cover conditions and alternatively the all weather capability of sensors operating in microwave region play an important role in a tropical country like India where the persistence of cloud cover is high. This paper deals with the evaluation of ERS-1 Synthetic Aperture Radar (SAR) data in conjunction with Indian Remote Sensing Data (IRS) LISS-II optical data in synergistic combinations with microwave data for land use/land cover mapping and assessment. Here part of East Godavari District of Andhra Pradesh, India covering coringa reserved forest and Kakinada town and its surroundings covering 1900 sq.kms of area has been considered for the study. The area selected encompasses a variety of land use/land cover features like urban areas, croplands, plantations, mangroves, marshy and waterlogged areas, salt pans, waterbodies and aquaculture sites. The data from coherent imaging systems like SAR are corrupted with speckle noise and in order to minimise speckle different filtering techniques have been applied on SAR raw data. It has been observed that the 5x5 median filter could adequately minimise the speckle interference in feature delineation. Land use/land cover maps have been generated from raw and filtered SAR data sets and also the mapping accuracy has been estimated using Kappa and proportional accuracy statistical methods. The increased mapping accuracy in filtered SAR data has been attributed essentially to reduction of speckle noise. False color composites (FCC) of different combinations of filtered and registered data products of LISS-II and SAR data have been generated. Intensity-Hue Saturation (IHS) transformation and Principal Component Analysis have been applied to the registered data sets. Ranking table quantifying advantages of different combinations has beenprepared. From the analysis, it has been concluded that synergistic combination of optical and microwave data helps in delineating land use/land cover categories upto Level-III compared to individual data sets.
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