DFT based Hiding Technique for Colour Image Authentication (DFTHTCIA)

In this paper a novel data hiding technique in frequency domain has been proposed using Discrete Fourier Transform (DFT) for colour image authentication and secret message transmission. Image authentication is done by embedding message/image in frequency domain by choosing image blocks of size 2 × 2, called mask, from the source image in row major order and transform it into the frequency domain using DFT. Here three algorithms are developed for embedding secret data into the source image. In the 1 algorithm two bits of authenticating message/image/message-digest are fabricated within the real parts of each source image byte except first frequency component of each mask and in 2 and 3 algorithm three and four bits of authenticating or secrete data are embedded respectively. In all the proposed techniques the dimension of authenticating image followed by message digest (MD) and the content of authenticating message/image are embedded. Inverse DFT (IDFT) is performed on embedded data to transform embedded frequency component to spatial component. In order to keep the quantum value positive and non negative in spatial domain a strong and robust technique is incorporated mainly on the first frequency component and sometimes on other component depends upon situations. The decoding is done by applying the reverse algorithm. Experimental results conform that the proposed algorithm performs better than DCT, QFT and SCDFT schemes.