Study On Algorithm Of Steganography For GIF And BMP Image

Computer and Internet technology develop rapidly. Network security protocols and traditional cryptographic techniques exited are constantly being challenged. It is never be discarded how to better protect the security of data transmitted over the Internet for the government, military, financial and business areas, etc. Information hiding makes the characteristics of secret information transmission be the performance of the carrier, so the others are not easy to feel the existence of the secret information. The information hidden has an important position in the field of information security.This paper researches the algorithms of steganography for GIF and BMP Image. After the Introduction to the formats of GIF image and BMP image and the existing algorithm of steganography for GIF and BMP Image, the paper proposes two algorithm of steganography for GIF images and improves one BMP-based algorithm of steganography. In this paper, the main work is as follows:1). A more efficient content-based Multi Constitution Multi Bits Steganography for GIF Images is introduced. The algorithm does not change the color palette, so the palette can be modified for resisting to some operations. Multiple bits of the secret information can be embedded in the index matrix of the carrier GIF image per pixel. The algorithm is good on visibility and with a large key space. Compared to the EzStego algorithm and the MBS algorithm which is very famous in recent years, MCMB is better than these two algorithms on visibility when embedding the same amount of secret bits.2). A Multi Bits Steganography for GIF Images based on decoding table of linear code is introduced. The algorithm combines Decoding Table of Linear Code and Steganography for GIF Images. Compared with traditional algorithm, the algorithm not only improves the amount of secret information which can be embedded 1 to 7 bits of secret information in a pixel in theory, but also brings better invisibility of steganography at the same carrier of GIF images and the same amount of secret information.3). After researching the Three-pixel Block Information Hiding Algorithm for BMP images, the paper improves the algorithm to Two Bits and Three-pixel Block Information Hiding Algorithm by replacing the least significant two bits of each pixel instead of replacing the whole eight bits of each pixel. The algorithm uses the size relationship of the last two binary values of the three pixels to define the'Size Ring', according which and the mapping of three bits binary to embed secret information. Experiment and theory show that the algorithm brings greatly improved on the invisible capacity of making information hidden compared with the Three-pixel Block Information Hiding Algorithm and the two LSB algorithm under the same embedded quantity.