Аннотация:Exchange of data over the open networks and internet is rapidly growing so security of the data becomes a major concern. One possible solution to this problem is to encrypt the data. The data can be text, image, audio, video etc. In today's world most of the multimedia applications involve images. Image encryption has applications in internet communication, multimedia systems, medical imaging, telemedicine, and military communication. Although we may use the traditional cryptosystems (such as RSA and DES) to encrypt images directly, it is not a good idea as image size is almost always greater than text. Therefore, traditional cryptosystems need much time to encrypt the image data. Security often depends on keeping the key secret. Cracking key used for encryption must be very difficult task. There have been many attacks or approach designed to crack the key for well-known algorithms. One way to make a system more secure is to change the key on periodic basis. Our work focuses on generating dynamic key using color image so that more security against many attacks can be achieved.