Steganographic Techniques of Data Hiding using Digital Images
Babloo Saha, Shuchi Sharma · 2012
Steganography word is of Greek origin and essentially means concealed writing. Protection of the transmitted data from being intercepted or tampered has led to the development of various steganographic techniques. Steganography has been manifested long way back during the ancient Greek times. Greek tyrant Histiaeus in 499 BC shaved the head of his slave and wrote message on his scalp. After the hair grew back, slave was dispatched with the hidden message. Pliny the Elder explained how the milk of the Thithymallus plant dried to transparency when applied to paper but darkened to brown when subsequently heated, thus providing the way for hiding information. Giovanni Battista Porta described how to conceal a message within a hardboiled egg by writing on the shell with a special ink. In world war II long sentences of regular letters were used to disguise secret messages. With the tremendous advancement in digital signal processing, use of internet, computing power, steganography has gone digital. The data hiding process starts by identifying a cover image’s redundant bits, i.e., those that can be modified without destroying its integrity. The embedding process then creates stego-image by replacing subset of these redundant bits with the bits of the message to be hidden. Generic steganography process is shown in Fig 1. In digital image steganography, the secret message is embedded within a digital image called cover-image. Cover-image carrying embedded secret data is referred as stego-image. 1.1. Applications of Steganography