Multimedia Security, Volume 1

3Codes and Watermarks

Pascal LEFÈVRE¹, Philippe CARRɹ and Philippe GABORIT²

¹ XLIM, CNRS, University of Poitiers, France

² XLIM, CNRS, University of Limoges, France

In this chapter, we propose to analyze the principle of digital watermarking of images through the prism of the use of error-correcting codes in a very specific framework, namely the so-called robust watermark. The process of watermarking can be studied according to the formality of the transmission of information in a possibly noisy channel. These error-correcting codes have demonstrated their value in this type of application, which is why they were quite naturally introduced in the context of watermarking. In this chapter, classical Hamming error-correcting codes as well as Bose-Chaudhuri-Hocquenghem (BCH) codes and Reed–Solomon (RS) codes are associated with random and packet error structures. In order to illustrate the impact and benefit of using error-correcting codes, we deploy a simple use case based on by index modulation watermarking. In particular, we discuss the differences in behavior regarding robustness, according to the attack and the code used. We conclude the chapter by introducing a more original code and show how a specific code can respond to a particular problem, here the problem of cropping.

3.1. Introduction

Over the years, several watermarking paradigms have emerged due to the protection requirements of many applications. It is very easy to modify or falsify images because of public access ...