Majlesi Journal of Multimedia Processing Vol. 4, No. 4, December 2015 9 Introducing a new method of Robust Digital Image Watermarking against Cropping and Salt & Pepper Noise using Sudoku Shadi. Saneie 1 , Alireza. Naghsh 2 1,2- Department Of Electrical Engineering Najafabad Branch, Islamic Azad University, Najafabad, Isfahan, Iran Email: shadi.saneie@yahoo.com Email: naghsh.a@pel.iaun.ac.ir (Corresponding author) Received June 2015 Revised Oct. 2015 Accepted Nov. 2015 ABSTRACT: With rapid development of digital technology, protecting information such as copyright, content ownership confirmation has become more important. In image watermarking, information of the image is inserted such that the visual quality of the image is not reduced and the receiver is able to get the required information. Some attacks such as image cropping and salt & pepper noise, destroy the watermark’s information. In this article, a new watermarking scheme is proposed which is robust against salt & pepper noise and tough cropping. A Sudoku table comprises 9 regions, each row and column of the table contains different numbers from 1 to 9. In the proposed scheme, Sudoku table and both watermarking approaches based on spatial domain and transform domain are used. Robustness of watermarking against cropping attack is 86% and its robustness against salt and pepper noise is about 75%, which shows good and effective performance of the proposed scheme. KEYWORDS: Digital Image Watermarking, Sudoku, Spatial domain, Transform domain, Cropping, Salt & Pepper Noise. 1. INTRODUCTION Now a days, transferring saved information, documents, images, films and audio files in digital form is very common. For most people, transferring digital files over internet is a daily task. Due to rapid development of digital technology and widespread use of internet, living has become considerably easier than before. Despite this convenience, there are some difficulties. Creating unlimited copies of information, changing their contents and rapid transmission of the copies in the internet are very easily done. Thus, protecting copyright, ownership confirmation and detecting interference in information seems very important. One of the solutions for this problem is to use digital watermarking techniques. Watermarking registers inserting information in formats like audio, image, film and etc, in a host signal. Host signal can also be audio, image or any other digital document [1]. In image watermarking, information of the image is inserted such that the visual quality of the image is not reduced and information is transferred to the final user. Example of watermarking is observed in currency, government documents, and stamp and information communication. Fig. 1. Typical watermarking system framework Watermarking provides a certainty level for documents’ ownership confirmation [2]. Each watermarking algorithm comprises two fundamental stages: watermark embedding and watermark extraction. In Figure 1, schematic of a watermarking system is shown. For embedding information, spatial domain, transform domain or both can be used. Watermark extraction is also done through watermark correlation with reference image or dependent of the reference image, though blind watermarking. Embedder Extractor Compare Attacks Watermark Watermarked content Distorted content Secret key to increase security Removed watermark Secret key to increase security