A MODIFICATION OF THE LEAST SIGNIFICANT BIT STEGANOGRAPHY METHOD IN SVG IMAGES

Abstract

This paper proposes and investigates a modification of the least significant bit (LSB) replacement method for steganographic data hiding in SVG images by simultaneously hiding data in both the coordinate and color components. A comprehensive comparative analysis of the effectiveness of the proposed method of embedding data into the vector SVG format versus the raster BMP format is also conducted. An analysis of recent publications reveals a research gap in the field of steganographic use of vector web resources, which, due to their architecture, remain less studied compared to raster images. The research methodology describes the process of standardizing input graphic objects and a step-by-step algorithm that implements both the classical color modification by replacing the least significant bits and the proposed hybrid strategy. This method involves splitting the secret message stream between the text-based hexadecimal codes of the color palette and the numerical coordinates of the geometric primitives of the drawing paths. The results of the study contain detailed experimental data for various numbers of replaced LSBs. It is demonstrated that isolated color-based hiding in SVG has low capacity due to the limited number of tags. Switching to coordinate modification increases the usable capacity almost by ten. The proposed hybrid method, which combines the embedding of secret bits into both the color and coordinate components allowed significantly increase the amount of hidden data. Using Peak Signal-to-Noise Ratio (PSNR) and the Structural Similarity Index (SSIM), it was found that the vector format demonstrates resistance to quality degradation as number of hidden bits increases: the PSNR value for SVG remains stable regardless of bit depth, whereas BMP quality decreases proportionally and leads to the appearance of visual artifacts.