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 evaluatethe efficiency of encryption. Also the time of encryption in the case ofJPEG and BMP image was measured for a number of selected imagesthat are different in their size. Finally, a measure for the quality ofencryption was introduced and applied to each case.The performance results of the application of DES on images saved inBMP or JPEG format have been shown in graphical forms. Also theresults of measuring the mean square error between the original imageand the decrypted image were documented in tabular and graphicalforms. In addition the results of measuring the encryption tune of imagesin each of the two cases are presented in tabular forms for a selectedgroup of images. Finally the results of measuring the quality ofencryption in each case were presented in histograms and plotted curves.The software used for implementing DES and its application on the bothJPEG and BMP images and making the comparison study is written inC++, it was performed on a 400 Mllz Fentium II PC machine with 32megabytes main memory, running on Windows 98. All programs wereimplemented in Microsoft/visual C ++6.0. The Paint Shop Pro version 7was used to display the encrypted image and decrypted one, and toextract the difference image.