| Algorithm |
Least Significant Bit (LSB) |
Masking and Filtering |
Discrete Cosine Transformations (DCT) |
| Best Used With Which Compression? |
Lossless |
Lossless or lossy |
Lossy |
| Best Used With What Types of Images? |
24-bit Bitmap, grayscale GIF |
24-bit images, grayscale images, can be used with JPEG |
JPEG |
| When Algorithm Should be Applied |
Anytime before stego-image is saved |
Depends on compression scheme; if lossy then during compression, if
lossless then anytime before saving the stego-image |
During compression |
| Strength Against Image Manipulation |
Low |
Medium |
High |
| How Algorithm Works |
Hides the bits of the message among the least significant bit
of the colors of a pixel or the pixel, depending on whether the
image is 8-bit or 24-bit. |
Works like paper watermarks by creating markings in the image.
Used done by modifying the luminance of parts of the image. |
Uses the compression algorithm for the image type, then modifies
the values being compressed in order to hide the message. The
message is hidden in these values using LSB. An 8x8 pixel block will
contain at most a couple bits of the message. |
| Efficiency |
Must go through each pixel, sometimes each color of the pixel,
until entire message is hidden |
Can skip pixels to go to desired location |
Must go through normal compression algorithm, then change each
result from the algorithm until the message is hidden |