Image Authentication Technique Based on DCT (IATDCT)

Abstract

In this paper a novel steganographic technique based on Discrete Cosine Transform (DCT) is demonstrated for image authentication in frequency domain. The transformation is implemented on sub-image block called mask of size 2 x 2 of spatial components in row major order for the entire image. Single bit of authenticating secret message/image is fabricated in the real part of the frequency component of 2nd and 3rd carrier image byte of each sub-image block. A minor re-adjustment is incorporated only in the first component of each sub image block after embedding to keep the pixel values positive and non fractional in spatial domain. Robustness is achieved through embedding secret bits in variable positions of the carrier image byte determined by random function and subsequent masking. Experimental results depict enhanced performance of the proposed watermarking technique.