Digital Watermarking

•Digital image processing is the use of computer algorithms to perform image processing on digital images which is a subfield of digital signal processing.

•Basic Types of Images • Binary images •Indexed images •Grayscale images. •True color images.

The process of embedding information into another object/signal is termed as watermarking. The signal can be audio, text , picture or a video.

Types of Watermarks Visible watermark The information is visible which is a text or a logo which identifies the owner of the media.

Invisible watermark An invisible watermark is an embedded image which cannot be perceived with human’s eyes and are intended to prevent or deter unauthorized copying of digital media.

Visible Watermark Original Image

Watermarked image

Invisible Watermark Original image

Watermarked image

Detection of modification of an image using Watermarking Technology.

(a)Image protected with Watermarking technology. (b)Tampered image. (c) Image after running the Watermark Detection Technology.

Cryptography is secret writing In cryptography the message will be encrypted and cannot be decoded without knowing the proper key. Steganography is the act of adding a hidden message to an image or other media file. It is similar to encrypting a document, but instead of running it through a cypher, the document is broken up and stored in unused, or unnoticable, bits within the overall image. Watermarking attempts to hide a message as it is to tag a document for later identification. Watermarking is used to protect the copyright of the original owner

Watermarking life-cycle phases

Steps in the watermarking system • Embedding The information to be embedded is called a digital watermark whereas the signal where the watermark is to be embedded is called the host signal In embedding, an algorithm accepts the host and the data to be embedded and produces a watermarked signal. • Attack During transmission of the signal to a person, If this person makes a modification, this is called an attack. • Detection It is an algorithm which is applied to the attacked or unmodified signal to attempt to extract the watermark from it.

How can an image be watermarked ? • Visible watermarks on images can be easily achieved thorough image editing software. • Invisible watermarks implements several different watermarking algorithms which can be done in two ways. 1. Spatial domain. 2. Frequency domain

Spatial Domain Spatial domain watermarking methods use blockxblock based watermarking. e.g. they embed the watermarks on a randomly selected 8x8 blocks of pixels of the image.

Frequency domain To embed a watermark, a frequency transformation is applied to the host data. Then, modifications are made to the transform coefficients. Possible frequency image transformations include the Discrete Fourier Transform

• 1. Correlation based Watermarking.

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2. CDMA Watermarking.

• Discrete Cosine transform PN sequence watermarking • Mid-Band coefficient Exchange Watermarking

• Imperceptibility :In watermarking, we traditionally seek high fidelity, i.e. the watermarked work must look or sound like the original. • Robustness: It is more a property and not a requirement of watermarking. The watermark should be able to survive any resonable processing inflicted on the carrier. • Security: The watermarked image should not reveal any clues of the presence of the watermark, with respect to un-authorized detection.

1. 2. 3. 4.

Copyright protection Fingerprinting Copy protection Image authentication

Purpose of the Project   • Implementing different watermarking algorithms and observed the imperceptibility of the watermark embedded using each algorithm

• SOFTWARE: MATLAB 7.0 • PLATFORM: WINDOWS 98/ 2000 /XP/ Vista

Conclusion

Digital watermarking focuses on embedding information inside a digital object such that the embedded information is in separable bound to the object.

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