Steganography using the twelve square substitution cipher and an index variable

Abstract

In this paper we are proposing a technique for secret communication between Alice and Bob. We are using both cryptography and steganography. Firstly, we encrypt the secret message using our new cipher algorithm called twelve square substitution cipher algorithm, and then embed the cipher text in the carrier image in 6 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> and 7 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> bit locations or 7 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> and 8 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> bit locations or 6 and 8 bit locations of the different pixels (bytes) of the carrier image depending on the value of an index variable. Here the 8 bit means the least significant bit (LSB) location, the 7 bit means the LSB minus one location and the 6 bit means the LSB minus two location. The index variable value can be 0 or 1 or 2. The index variable value will change from 0 to 1 or 1 to 2 or 2 to 0 after each embedding. The initial value of the index variable depends upon the length of the cipher text. After embedding the resultant image should be sent to the receiver and receiver should retrieve the cipher text from the said locations and then decrypt by using the twelve square cipher algorithm to get the secret message. The embedding locations are not same in all pixels, so it is a stronger approach. The algorithm is implemented using Java programming language. The experimental results says that the algorithm performs well.