Introduction - If you have any usage issues, please Google them yourself
In 2005, Hwang et al. [17] proposed a time-stamping protocol for digit
watermarking. They claimed that their scheme is secure against attacks. However, in this
article, we will show that their scheme is not secure enough for that when the owner of
the image sends both the encrypted session key and image to the TSS, the attacker can
intercept these transmitted data. Then, he can launch an off-line attack to analyze these
intercepted data. We will describe the attacker’s action in this article. After that, we
propose an improved scheme to prevent this off-line attack.
Cryptanalysis of Hwang-Changs a Time-Stamp Protocol for Digital Watermarking.pdf