A High Capacity Email Steganography Scheme using Dictionary

The main objective of steganography is to conceal a secret message within a cover-media in such a way that only the original receiver can discern the presence of the hidden message. The cover-media can be a text, email, audio, image, and video, which can be transmitted through a public channel, such as the Internet. By extending the use of email among Internet users, the provision of email steganography methods has been highly considered. In other words, email-based steganography becomes one of the most popular techniques for text steganography. An email steganography scheme hides the secret message into either the email body or email addresses. However, current approaches suffer from a limited capacity, which leads to a tradeoff between the security and the capacity of the steganography scheme. In this paper, we propose an email steganography scheme using a dictionary-based compression. The proposed scheme provides an unlimited steganography capacity along with a promising security level. In the first step of the proposed scheme, the secret message is compressed and encoded to a bitstream using a dictionary. After that, the bitstream is divided into several parts based on the number of characters in the cover text. Each part of the secret message is then converted to a decimal value, and an email address is generated using both the decimal value and the secret keys. Finally, the cover-text, which is the email body in our scheme, is sent to all generated email addresses as well as the original receiver. Experimental results show that the proposed scheme not only provides an unlimited steganography capacity but also generates fewer email addresses comparing to the state of the art in the steganography literature.