Copyright Protection Using Non Linear Forward Feedback Shift Register And Error-Correction Technique
5. Brief of how the steganography works
Hiding data in an image requires two files. The first file, called the “cover-image”, will be the innocent looking image that holds the hidden information. The second file will contain the information to be hidden. When combined, the two files will generate a “stego-image”. There exists a number of ways to create a stego-image from the given cover-image and the data to be hidden. These include least significant bit(LSB) insertion, masking and filtering, redundant pattern encoding, and other spread spectrum methods.
6. Brief of icorporating hte crypted and error coded binary pattern in hte Image
The amount of data that can be hidden in the Image directly depends on the size of the image. To a computer, an image is an array of numbers that represent light intensities at various points (pixels). Digital Images are generally stored as storing each pixels color information with a particular header telling how the image should be read and interpreted. We leave the header as it as and modify the pixel’s color information bits. The amount of the color information stored for each pixel depends upon the color depth of the image.
4.1 Calculating R values
In first step, we place each bit of the original data in its appropriate place in the 7bit unit. Then we calculate the even parity for the various bit combinations. The parity value for each combination is the value of the corresponding R bit. The value of the cryptic ‘A’ is 00000000.Now we will apply the error code in it first taking the first 4 bits and then applying the steps we just mentioned we get a seven bit error coded data as 0000000.Now again to the next 4 bit we do the same and get another seven bit coded data as 0000000. So the cryptic ‘A’ has become 0000000 0000000 after error coding.
4.2 Error Detection & Correction
Now imagine that by the time the above transmission is received a error in the bit has occurred. The receiver recalculates four new VRC using the same sets of bits used by the sender plus the relevant parity(R) bit for each set. Then it assembles the new parity values into a binary number in order of r position (R4R2R1). Now the decimal value we get is the precise location of the bit in error. Once the bit is identified, the receiver can reverse its value and correct the error. Now after the bit sequence has been recovered we compress the bit sequence which we have duplicated 8 times, during error coding. We may find that many bits in the block of 8 bits have changed, so we compress this block to a value which is in majority in the block. This makes our error coding technique very robust and useful.
How hte steganography works
The design principle of steganographic systems is based on the premise that most communication channels – such as telephone lines and radio broadcasts – transmit signals accompanied by some kind of noise [4, 5]. This noise can be replaced by a transformed secret signal indistinguishable from the noise without the secret key. In this way, the secret signal can be transmitted undetected. In the same way hiding data in an image requires two files. The first file, called the “cover-image”, will be the innocent looking image that holds the hidden information. The second file will contain the information to be hidden. When combined, the two files will generate a “stego-image”. There exists a number of ways to create a stego-image from the given cover-image and the data to be hidden. These include least significant bit (LSB) insertion, masking and filtering, redundant pattern encoding, and other spread spectrum methods [4, 5, 6].
Incorporating the crypted and error coded binary sequence in the Images
The amount of data that can be hidden in the Image directly depends on the size of the image. To a computer, an image is an array of numbers that represent light intensities at various points (pixels). Digital Images are generally stored as pixels color information with a particular header telling how the image should be read and interpreted. We leave the header as it as and modify the pixel’s color information bits. The amount of the color information stored for each pixel depends upon the color depth of the image. The bit stream is hidden in the Image using the LSB insertion technique.