Maryam Hamrahi - Young Researchers and Elite Club varzegan Branch, Islamic Azad University,varzegan, Iran
Zahra Hamrahi - Young Researchers and Elite Club, Ahar Branch, Islamic Azad University, Ahar, Iran
Naser Jafari - Student of the Faculty of Electrical and Computer Engineering, Varzaghan Azad University,Varzghan, Iran

Digital watermarking applications include content protection for audio and video content, forensicsand piracy deterrence, content filtering, communication of ownership and copyrights, document andimage security, broadcast monitoring and many more. Watermarking technology is an emergingfield in computer science, cryptography, signal processing and communications. Watermarks can beattacked in a variety of different ways, and each application requires its own type of security. Thesecurity requirements for a watermarking system vary greatly from application to application. Insome applications watermarks need not be secure at all. In general, any watermarking scheme(algorithm) consists of three parts: the watermark, the encoder (insertion algorithm), the decoderand comparator (verification or extraction or detection algorithm). A watermarked image is likely tobe subjected to certain manipulations, some intentional such as compression and transmission noiseand some intentional such as cropping, filtering, etc. A number of attacks watermarking have beenproposed in literature. This paper is a tutorial in general watermarking principles and focuses onattacks various watermarking techniques. As attacks are found that work against existingtechniques, it is likely that new techniques will be developed that overcome these deficiencies

Digital watermarking; technology; algorithm; attacks.