Counterfeiting attack on adjusted expanded-bit multiscale quantization-based semi-fragile watermarking technique

Semi-fragile watermarking methods are mainly characterized by their robustness against unintentional attacks such as regular image processing and their fragility against intentional attacks aiming to alter signal contents. Thus, these methods need to provide correct robustness and fragility. However, numerous factors impede the achievement of these two objectives. The fact that the watermark is not dependent on the content of the image (the medium considered in this study) and also the semi-fragile method is not block-wise dependent, make the method vulnerable to intentional attacks. Recently, an image authentication method has been proposed, which despite the use of a secret key in generating the watermark, suffers from the preceding vulnerabilities. Thus, in this paper we aim to present a counterfeiting attack and demonstrate that the method is not even fragile against complete counterfeiting, making it incapable of detecting image tampering. Essentially, the proposed attack enables the attacker to counterfeit the watermarks belonging to any number of 4×4 blocks and embed them in arbitrary blocks. The results indicate that the proposed attack successfully deceives the method.