Secure hybrid robust watermarking resistant against tampering and copy attack

Digital watermarking appears today as an e.cient mean of securing multimedia documents. Several application scenarios in the security of digital watermarking have been pointed out, each of them with di/erent requirements. The three main identi1ed scenarios are: copyright protection, i.e. protecting ownership and usage rights; tamper proo1ng, aiming at detecting malicious modi1cations; and authentication, the purpose of which is to check the authenticity of the originator of a document. While robust watermarks, which survive to any change or alteration of the protected documents, are typically used for copyright protection, tamper proo1ng and authentication generally require fragile or semi-fragile watermarks in order to detect modi1ed or faked documents. Further, most of robust watermarking schemes are vulnerable to the so-called copy attack, where a watermark can be copied from one document to another by any unauthorized person, making these schemes ine.cient in all authentication applications. In this paper, we propose a hybrid watermarking method joining a robust and a fragile or semi-fragile watermark, and thus combining copyright protection and tamper proo1ng. As a result this approach is at the same time resistant against copy attack. In addition, the fragile information is inserted in a way which preserves robustness and reliability of the robust part. The numerous tests and the results obtained according to the Stirmark benchmark demonstrate the superior performance of the proposed approach. ? 2003 Elsevier B.V. All rights reserved.