JSE_V4_N4_RP11 Manisha Sharma M.K. Kowar Journal on Software Engineering 2230 – 7168 4 4 74 79 Watermark, DCT, Image tampering, Quantization A watermarking technique for image authentication inserts hidden data into an image in order to detect any accidental or malicious alteration. In the proposed work, a watermark in the form of a visually meaningful binary pattern is embedded for the purpose of tamper detection. The watermark is embedded in the discrete cosine transform coefficients of the image by quantizing the coefficients proportionally according to the watermarked bit. Experimental results demonstrate the performance and effectiveness of the scheme for image authentication by maintaining good values for both, the Peak Signal to Noise Ratio (PSNR) and Tamper Assessment Function (TAF). April - June 2010 Copyright © 2010 i-manager publications. All rights reserved. i-manager Publications http://www.imanagerpublications.com/Article.aspx?ArticleId=1184