Watermarking of Digital Images — Current Techniques and Future Prospects

Abstract

Worldwide computer break-ins and unauthorized access to computer data are increasing. Securing the information stored in or communicated between personal computers has become an essential business practice as the number and applications of these machines increase. Conventionally, for example, the Data Encryption Standard (DES), although established some time ago, may be used to encrypt complete image data, but this can be quite time-consuming for, say, 640×480 pixel image files [1, 2].

This chapter reviews watermarking and encryption of images, and then describes ImgCrypt [3]. This provides secure image encryption and “wipe options” to prevent unauthorized access to one’s personal image collection. The ImgCrypt package uses the DES algorithm, together with pixel position transformation and neighbourhood encryption, to perform encryption and decryption functions.

Comparison may be made between this method and the conventional text-type method using DES. ImgCrypt encrypts the image data approximately 50 times faster than text-type methods. It is also a very secure encryption, and would not normally allow an intruder to get anywhere near to the image key. Message authentication is also applied here to verify that the contents of the image have not been altered and that the source is authentic.