As the telecommunication technologies grow rapidly, many applicationssuch as Internet, multimedia applications and military applications needto enter the era of visual communication, especially visual cryptography.Transferring images through network (especially Internet) makes themvulnerable to eavesDROPping or unauthorized users who may tap into thesystems, by reading the image or changing its content. So it is importantto employ the encryption mechanism to protect an image against imagedata reading, or data alteration, addition and deletion, especially imageswhich is related to the national security or classified researches.However there are many encryption methods which were used for imageprotection against data reading. All of them aim to hide all the details ofimage by converting it to ciphered image. Using encryption techniques ismore powerful way for this purpose.This thesis investigates the performance of the application of Dataencryption standard as a popular encryption scheme on two kinds ofimages, the Bitmap image which is the best choice for representing subtlegradations of shades and color such as screen shots or simple paintedimages, and the JPEG image which is the best choice for continuous toneimages such as photographs. The method of application of DES on theimage in each case is explained. A mean square error measure betweenthe original image and the decrypted image was considered to evaluateUpdating the model has been made for; 1) increase the number of studied years to nine years (1992-2000), 2) testing the effect of macro-economic and industry related factor on the performance evaluation of Egyptian construction companies. Theupdating of the model takes in to account the company-size effect on the performance evaluation of construction companies. Also. The study tested the validity of the ”Unsupervised Neural Network” technique to solve the problem. But this trial failedbecause this technique needs a large number of observations in the same year. This large number of companies was not available by any way. The model development aims to provide a proper tool for company’s manager, owners, shareholders, and funding agencies to evaluate the fmancial performance of construction companies. Inaddition, it helps company’s management to take the right financial decisions. It is developed based on Egyptian construction industry fmancial data for nine consecutive years (1992 - 2000). Three indices are developed: (1) company performance score(Se) using six fmancial ratios; (2) economy performance score (Se) and industry performance score (Si); and (3) performance index (PI). The developed model considers companies in four construction sectors: (a) general building construction;(b) heavy construction; (c) special trade construction; and (d) real estate construction.The fmal outcome of this study is a performance grade (G), which provides thefinancial situation of a construction company. This research is relevant to bothresearchers and practitioners. It provides models for practitioners’ usage to assesstheir companies and take the right decision to reform companies’ financial situation.In addition, it provides the researchers with regression models that they can build onand develop future researches in this subject.