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.