Analysis of Frequency Domain Image Steganography Using DCT, DWT and DCT With DWT

Abstract

Steganography is art and science of hiding communication. Image Steganography the process of hiding secret message in a cover image. Frequency domain hides the secret bits in the significant parts of the cover image. It tries to encode messages bits in the transform domain coefficients of the image. DCT and DWT come under frequency domain technique. This research evaluates the DCT, DWT and DCT with DWT algorithm using four measures: Peak Signal to Noise Ratio (PSNR), Mean Square Error (MSE), Number of Pixel Change Rate (NPCR) and Unified Average Changing Intensity (UCI) to measure the strength of the algorithms. The result shows that DCT with DWT is better than the two algorithms DCT and DWT. The PSNR value of the combined method has the highest value amount other two techniques. Using DCT with DWT, the original image and the stego image is similar without losing its image properties. The average PSNR value for DCT with DWT is 78.73, DWT is 76.62 and DCT is 73.56. The PSNR value of DCT with DWT method has higher value than other two techniques which verifies that the original image and stego image is similar without losing much of its image properties. But DCT and DWT has significantly has lower PSNR value, this value of PSNR results in a change of visual properties of the image. The average encoding value for DCT with DWT is 0.385045, DWT is 1.524587 and DCT is 1.09904 and decoding value for DCT with DWT is 0.173457, DWT is 0.117165 and DCT is 0.524236. The DCT with DWT has good differential analysis value which has average value 65.27% and 0.65 % for the NPCR and UACI respectively for different set of images used during analysis.

Keywords: Steganography, cover image, stego image, DCT, DWT