A hybrid approach to steganography embedding at darkest and brightest pixels

In this paper we present a technique for secure communication between two parties Alice and Bob. We use both cryptography and image steganography. We encrypt the secret message by using a new cipher which is extended from Hill cipher. Then the cipher text of the secret message is embedded into the carrier image in 6^th, 7^th and 8^th bit locations of the darkest and brightest pixels. Here 8^th bit means the least significant bit in a byte (i.e. called LSB). Here brightest pixels means having a gray value in the range 224 to 255 in 8 bit gray scale and darkest pixels means having gray value in the range 0 to 31 in 8 bit gray scale. As these darkest and brightest pixels are spread across the image randomly, the intruder will not be able to identify those pixels. After embedding the resultant image will be sent to the receiver, the receiver will apply the reverse operation what the sender has done and get the secret information.