WEEK 1 FYP 2

Title:

Research for Least Significant Bit (LSB)

Objective:

To know deeply about Least Significant Bit (LSB) used in Image Steganography

Content/Result:

• LSB (Least Significant Bit) substitution is the process of adjusting the least significant bit pixels of the carrier image. It is a simple approach for embedding message in to the image. The Least Significant Bit insertion varies according to number of bits in an image. For an 8 bit image, the least significant bit; in example; the 8th bit of each byte of the image is changed to the bit of secret message. For 24 bit image, the colours of each component like RGB (red, green and blue) are changed. LSB is effective in using BMP images since the compression in BMP is lossless. But for hiding the secret message inside an image of BMP file using LSB algorithm it requires a large image which is used as a cover. 

• LSB substitution is also possible for GIF formats, but the problem with the GIF image is whenever the least significant bit is changed the whole colour palette will be changed. The problem can be avoided by only using the gray scale GIF images since the gray scale image contains 256 shades and the changes will be done gradually so that it will be very hard to detect. For JPEG, the direct substitution of steganographic techniques is not possible since it will use lossy compression. So it uses LSB substitution for embedding the data into images. 

• For example, the following grid can be considered as 3 pixels of a 24-bit color image, using 9 bytes of memory: 

                                               (00100111 11101001 11001000)

                                               (00100111 11001000 11101001)

                                               (11001000 00100111 11101001)

When the other image, which binary value equals 10000001, is inserted, the following grid results:

                                              (00100111 11101000 11001000)

                                              (00100110 11001000 11101000)

                                              (11001000 00100111 11101001)

Left is the Original Image. Right is the image after LSB substitution

Conclusion:

LSB is the process of adjusting the least significant bit pixels of the carrier image. It is a simple approach for embedding message intothe image. The Least Significant Bit insertion varies according to number of bits in an image. LSB is effective in using BMP images since the compression in BMP is lossless