A Session based Spatial Domain Multiple Image Hiding Technique using Variable Bit Replacement and Multiple Passwords

For hiding secret information in images, there exists a large variety of Steganography techniques. The least significant bit (LSB) insertion method is the most common and easiest method for embedding messages in an image in spatial domain but it has some limitations such as it is easier to understand using steganalysis, this limitation has been overcame in this work. This work intends to embed multiple images in a single cover image. Three images can be embedded within a single cover image in its three different color channels (RGB) and they are embedded in between least significant bit (LSB) and moderately significant bit (MdSB). Three different passwords which are later converted into keys are used for three different color channels. Three different keys of 64 elements are generated from three different passwords. The key consists of the position values of a colored channel of the cover image where the information of a grey image is embedded using variable bit replacement (VBR) technique. Three different channels are combined to form a stego image and later grey images are retrieved from the stego image similarly. This transition of password to key and also the dependency on key imposes greater security. Another important aspect is that the same stego image bears different meaning for different receiver.