A common way of resisting protocol attacks is to employ cryptographic techniques so that provable security can be retained. However, some desired requirements of watermarking such as blind detection and robustness are lost. This paper studies the issue of security against protocol attacks based on a mesh-based media hash-dependent image watermarking approach while maintaining the aforementioned requirements. Our main contributions include (1) media hashing instead of cryptographic hashing is used so that blind detection is still satisfied; (2) robustness against signal processing attacks is retained; (3) the difficulty of resisting ambiguity attack is derived to be equivalent to that of resisting challenging geometric attacks including cropping with larger parts discarded and rotation with larger degrees so that an acceptable trade-off between false positive and false negative can be achieved.