DIGITAL STEGANOGRAPHY FOR ASCII TEXT DOCUMENT

Abstract

This dissertation endeavors at evolving portentous novel secure steganographic bit embedding schemes for digital ASCII text document besides suggesting enhancement in some existing text-centric steganographic methods. Further, a cover generation algorithm for the said purpose is also conferred. Our proposed algorithms uses substitution technique for embedding / hiding secret message bits inside the text-cover whereas our cover generation algorithm exploits statistical characteristics of randomly generated data for data hiding purpose. To contrast our proposed schemes with prevalent schemes we have quantified the test results using Hamming distance, Levenshtein metric (also called edit distance) and Jaro-Winkler distance, where to elaborate on the quality of quantified results we have plotted probability distribution of Cover and Stego (Text) Object for visual analysis. Security of prevailing and newly proposed Steganographic schemes is gauged using “Known Cover and Known Message Attacks” where “Chosen Message Attack” instantly reveals the logic behind prevalent Steganographic schemes. Our experimental results are in confirmation with generally accepted evaluation metrics for gauging Steganographic Systems. Moreover, our suggested bit embedding methods does not increase or decrease the size of original Cover file but yet increases its bit embedding capacity. Also, saving the Stego Object in Portable Document Format (.pdf), and / or MS Word (.doc) file (including Notepad) and its retrieval thereafter does not suffer from any information loss. The advantage of our proposed Cover (as fake cryptogram groups) generation method is that the Stego Object can be transmitted in printed form without requiring a code book for bit extraction at receiving end.