Multimedia Copyright Protection Technologies M. A. Suhail, I. A. Niazy

Introduction n There are various watermarking schemes applied to images. n The purpose is to give an overview about the field of invisible watermarking. n I will discuss the basic concept, procedure, applications, and requirements needed.

Digital Watermarking Concept n An identification code carrying information about the copyright owner, the creator of the work, etc., embedded permanently into digital data. n The purpose of embedding WM is to protect copyright or checking for modifications.

Types of Watermarks n There are two major categories for digital watermarking: –Visible Watermarking Like stamping on paper –Invisible Watermarking Far more complex I will focus on this category

Invisible Watermarking n Used to identify copyright data n The most suitable media for Watermarking are still images, video, and audio. n Unsuitable media include: –Executable files Converting it to conical format –Text Can be overcome by any commercial OCR.

How to Embed a Watermark Encoder (E) Key (PN) Original Media Signal (I 0 ) Watermarked Media signal (I water ) Watermark W

How to Embed a Watermark (continued) n The previous figure may be expressed as follows: –E(I 0, W) = I water –Embedding function ‘E’ modifies I 0 according to W.

How to Detect a Watermark Pirate productAttacked ContentDecoder Decryption Key Decoder response: Is the watermark W present? (Yes/No) Z

How to Detect a Watermark (continued) n Detection Function (Decoder) ‘D’ is defined as: D(R, I 0 ) = W’, where R is the watermarked signal. n W’ is compared with W, based on a correlation measure: where c is the value of the correlation, and  0 is a threshold.

Robust Watermarking Scheme Requirements n Imperceptibility (Perceptual Invisibility) –Penalty: less robustness n Robustness –Should survive intentional or unintentional attacks. –With images, resistance with geometric manipulation is still an open issue n Detectability –Small probability of failing

Digital Watermarking Techniques

Digital Watermarking Techniques (continued) n Spatial Domain Techniques –The modification of LSB (Least Significant Bit) of the host data techniques are used in the spatial domain. –LSB is modified using fixed magnitude NP sequence. –The LSB is insignificant, so the WM will be invisible. –WM easily corrupted by signal processing.

Digital Watermarking Techniques (continued) n Transform Domain Techniques –DCT (Discrete Cosine Transform) is based on dividing the image to square blocks of size 8  8, then modifying middle range frequency DCT coefficients of selected blocks. –Wavelet Transform: Multi-resolution based technique. –Fractal Transform: Very few works, because computationally expensive.

DCT Transform Watermark A mosque and its watermarked image with the detector response.

Commercial Software for Watermarking n Direct-Sequence –Adds noise to every element in the document. n and Frequency-Hopping –Selects a pseudorandom subset of data to be watermarked. n Direct-Sequence and Frequency- Hopping spread-spectrum are the methods used for most commercial watermarking.

Common Commercial Software n Digimarc® Uses Direct-Sequence methods to superimpose a watermark over an image. n SysCoP® is also another common software. n Commercial software lack some means of security in order to keep their prices within a reasonable bound.

Digimarc® Software Example (a) A watermarked image using Digimarc® software, and (b) the watermark information of (a) by Digimarc® displayed in a window. The bar in the bottom of the window displays the robustness of the watermark.

Conclusion n The concept and types of digital watermarking is defined. n Next, The usage and suitable media for invisible Watermarking is discussed. n Also the Digital Watermarking techniques were described. n Finally, some Commercial Software and their drawbacks were described.

Any Questions: n Please forward any questions to the following