Abdelkader H. Ouda Mahmoud El-Sakka, "Methods to correct Wong-Memon image watermarking scheme", TR#603, (22 pages), Computer Science Department, University of Western Ontario, October 2003, London, Ontario, Canada.
The increasing interest of digital images, as well as the Internet's popularization, has propelled image authentication schemes to the forefront of the digital images field. These schemes provide the ability to verify whether image integrity is authentic or not. Over the last few years, a large number of applications started to take advantage of these opportunities, and exposing new authenticating systems. Most of these systems attempt to utilize both digital watermarking and cryptography to guarantee a high level of security. While researchers regularly attempt to improve the security performance of these schemes, there will always be others investigating ways to attack and break them. Therefore, extra precaution should be taken when applying such schemes.
In 1998, Wong introduced a public-key watermarking scheme, aiming to detect unauthorized changes that may occur in a given image. In this paper, Wong's scheme is evaluated, and it is concluded that this scheme suffers from a serious security leak. This leak is due to the use of short keys within the public-key cryptosystem, needed to overcome an existing narrow bandwidth offered to hide the generated watermark. This paper suggests two solutions to protect against this leak. Solutions involve increasing the size of keys to protect the cryptosystem from attacks. Meanwhile, the same hiding bandwidth is efficiently utilized to accommodate the new proposed watermark, which gives similar detection accuracy as in Wong's scheme.
Keywords: digital watermarking, image authentication, digital signature, cryptography, ECC elliptic curve encryption, RSA encryption, MD5 Hashing, SHA-1 Hashing.