<FONT face=Verdana>A semi-fragile

block-wise and content-based watermarking method for tamper detection and recovery is presented in this paper. The non-overlapping blocks are used and the watermark bits for authentication are embedded into the middle frequency region of each block in the ST domain. The embedding process is based on the discovery which the sign of the most ST coefficients maintain invariant. For the recovery mechanism

the recovery bits generated from the compressed original image are embedded into the least significant bits (LSB) of the watermarked image. The degree of the authenticity is measured by the false positive detection rate and false negative detection rate. Simulation results demonstrated that our method is able to accurately detect and localize the tampered region as well as approximately recover it. Furthermore

as compare with the DCT and PST based schemes

our proposed method obtains better performance when both malicious and non-malicious manipulations are applied together.