. Qi and Xin
1 proposed a singular-value-based semi-fragile watermarking scheme for image
content authentication with five authentication
measures and performs a three-level process to authenticate image content and
localize tampered areas. Extensive experimental
results have shown that the proposed scheme was capable of identifying
intentional tampering, incidental modification, and localizing tampered regions.
However, it exhibited moderate performance
when it deals with attacks of small size image fragments.
Tomar 8 presented a scheme for tampering detection. The wavelet domain is considered as a secure
domain for watermark embedding. They applied two-level discrete wavelet
transform (2L-DWT) on color images by extracting the red, green and blue
components. Experimental results have shown that the algorithm worked only on large
and blurred attacks.
Saiyyad and Patil
9 proposed multimedia authentication and tamper detection scheme. They embedded
two watermarks into host image for authentication and tamper detection. They
used unique identification code as the first robust watermark which is then
embedded into image using 2L-DWT. The Hash code of the host image was
calculated and was used as a secondary watermark for tamper detection. However,
It was not working for all attacks.
Dhole and Patil
10 introduced a modified fragile watermarking
technique that can detect and recover the tampered image regions. This approach
produced resistance against various attacks using a non-sequential block
chaining technique which was created on the basis of secrete key. This modified
technique produced great amount of recovery from tampered regions. Here, they included
the watermark information and recovery information into the image blocks. The quality of watermarking was relatively low.
Chaluvadi and Prasad 11 proposed an efficient dual
watermark scheme for image tamper detection and recovery. In the proposed
algorithm each block in the image contained a watermark of other two blocks,
i.e. two copies of watermark of the whole image were maintained and second
chance for block recovery was provided in case one copy is destroyed. Experimental results have
shown low tamper detection rate which a limitation to be used only with grayscale