A Text Steganographic System Based on Word Length Entropy Rate

Abstract

The widespread adoption of electronic distribution of material is accompanied by illicit copying and distribution. This is why individuals, businesses and governments have come to think of how to protect their work, prevent such illicit activities and trace the distribution of a document. It is in this context that a lot of attention is being focused on steganography. Implementing steganography in text document is not an easy undertaking considering the fact that text document has very few places in which to embed hidden data. Any minute change introduced to text objects can easily be noticed thus attracting attention from possible hackers. This study investigates the possibility of embedding data in text document by employing the entropy rate of the constituent characters of words not less than four characters long. The scheme was used to embed bits in text according to the alphabetic structure of the words, the respective characters were compared with their neighbouring characters and if the first character was alphabetically lower than the succeeding character according to their ASCII codes, a zero bit was embedded otherwise 1 was embedded after the characters had been transposed. Before embedding, the secret message was encrypted with a secret key to add a layer of security to the secret message to be embedded, and then a pseudorandom number was generated from the word counts of the text which was used to paint the starting point of the embedding process. The embedding capacity of the scheme was relatively high compared with the space encoding and semantic method.