METHOD OF HIDING INFORMATION USING THE AES ENCRYPTION ALGORITHM AND THE LSB STEGANOGRAPHIC METHOD WITH PROTECTION AGAINST CROPPING AND STEGANALYSIS

Abstract

In an evolving era of rapidly increasing digital information volumes, ensuring its secure transmission is a critical task. The combination of steganography and encryption creates a powerful two-level security mechanism that simultaneously encrypts data and conceals its transmission. This paper proposes a method that implements two-level protection. The secret message is first encrypted using a reliable AES algorithm with a 256-bit key. This converts the source text into a pseudo-random sequence of bits, which complicates statistical analysis. Next, the encrypted data is embedded into a 24-bit color container image using a modified LSB method. The novelty of the approach lies in the following improvements: one full byte of the message is embedded into one pixel of the image, with its bits distributed across the RGB channels, which provides capacity; pixels are selected in a pseudo-random order using a pseudo-random number generator (PRNG), and a second PRNG is used for additional masking, providing additional protection against steganography analysis; The start of message embedding is shifted from the beginning of the file based on the image size, which protects the data when the steganographic container is partially cropped.

Standard metrics were selected to evaluate the effectiveness of the developed method: peak signal-to-noise ratio (PSNR), structural similarity index (SSIM), and normalized cross-correlation (NCC). Experimental analysis showed that the proposed method provides high-quality steganographic images. Even with maximum container filling (262,144 bytes), the PSNR remained high (56.67–56.76 dB), and the SSIM and NCC metrics were very close to 1, indicating minimal visual distortion. It is impossible to visually distinguish the original image from the stego container. A comparative analysis with other known methods (for 100,000 bytes) showed that the proposed algorithm has higher PSNR values (70.01–70.07 dB), confirming its effectiveness. The use of a double PRNG and embedding one byte per pixel ensures both high security and significant throughput. The developed hybrid method, which combines AES-256 encryption and modified LSB steganography with pseudo-random selection of pixels and bits, is an effective solution for the covert transmission of large amounts of data. The method provides a high level of security, resistance to steganography analysis, and visual invisibility of embedded data, as confirmed by high PSNR, SSIM, and NCC metrics.