Comparison of data hiding using LSB and DCT for image

Steganography is the art and science of hiding information by embedding data into cover media. There are two main domains namely spatial and frequency domain. In this project, a comparison is made between hiding in spatial domain using LSB technique and hiding in frequency domain using DCT technique. Various BMP cover images with 256x256 and 512x512 resolutions for LSB and DCT techniques are used in the experimentations. For DCT technique, various BMP image is converted to JPEG image. Then data is hidden into the JPEG cover image using DCT technique. After that, the JPEG stego image is converted back to BMP stego image. These BMP stego images from LSB and DCT are compared using PSNR. Results from these experiments show that 75% of the stego images hidden using LSB has shown higher PSNR values than stego images hidden using DCT. This means that the stego image hidden using LSB has shown a much closer similarity to the cover image than stego image hidden using DCT, thus much harder to detect hidden data in the stego image by LSB

Synthesis and characterization of polyurethanes crosslinked by polyrotaxanes consisting of half-methylated cyclodextrins and PEGs with different chain lengths

Three polyurethanes (PRX1500Me-PU, PRX4000Me-PU, and PRX6000Me-PU) crosslinked by polyrotaxanes (PRXs), which consist of half-methylated α-cyclodextrins (CyDs) and poly(oxyethylene)glycols with different chain lengths (PEG1500, PEG4000, and PEG6000), were synthesized. The filling ratios of CyD in PRX1500, PRX4000 and PRX6000 are 75, 63 and 37%, respectively. A polyurethane crosslinked by half-methylated CyD (CDMe-PU) was also prepared for comparison of their structure and properties. ATR-FT-IR spectra of the PUs showed that the formation ratio of hydrogen bond between the PU chains around PRXs increased with increase in the filling ratio. DSC and dynamic viscoelastic measurements and tensile tests for the PUs revealed that (i) reorganized-crystallization of the soft segment chains of PRX1500Me-PU easily occurred because of formation of a pure phase for them; (ii) the thermal and physical behaviors of PRX6000Me-PU are similar to those of CDMe-PU because CyDs as the crosslink points disperse in a similar fashion in the PUs; (iii) the PRX4000 with the moderate filling ratio of CyD in PRX4000Me-PU makes slow reorganized-crystallization of the soft segment chains in the PU as well as improves the tensile performance among the PUs