A forward email based high capacity text steganography technique using a randomized and indexed word dictionary

Abstract

Text steganography is inherently difficult due to minimal redundant information space to hide secret payload. The same fact limits the hiding capacity and security too. In this study, a novel technique has been proposed using a randomized indexed word dictionary, and a list of email addresses to increase the hiding capacity and security. A forward email platform has been used as the cover, and email addresses in the carbon copy (CC) field contain secret data that are encoded using a randomized index-based word dictionary. The email username list and indexed word dictionary are both pre-shared between the communicating parties. But during every new communication, a random bitstream (temporary stego-key) is generated from the system time and communicated separately using public-key cryptography. This temporary stego-key is used to randomize the index values of the words in the dictionary. Most of the existing state-of-the-art techniques provide a hiding capacity of 6–10%. The proposed scheme achieves a capacity of 12.17% using some common secret text and email body text (cover text) as used in all other studies. The proposed technique provides higher hiding capacity and security by randomizing the word indexes every time using temporary stego-key. It is also free from statistical attacks, OCR based attacks, and does not depend on the use of any particular text processor.