Digital Steganography—An Introduction to Techniques and Tools

Abstract

Steganography is the art and science of hiding information. In the digital realm, steganography (which literally means “covered writing”), involves hiding data or messages in digital files and other digital structures. The carriers holding the hidden content may appear to be innocuous, and would be ignored by a casual observer. The field of digital information hiding has grown significantly since the 1990s. Evidence of this growth can be seen at workshops on information hiding and in occasional reports of use by criminals and terrorists as reported in the popular press. In contrast to cryptography where the message is encoded, the purpose of steganography is to hide the fact that a message is being sent. Once encoded, a cryptographically altered message typically appears unrecognizable and would raise suspicions. The primary advantage of steganography over cryptography is that the carriers do not attract attention to themselves, to messengers, or to recipients. Modern information technology enables novice computer users to create steganographic messages, transmit, and unhide them without special expertise. This article presents an overview of steganography’s history and the categories of steg methods, followed by a discussion of the application areas for steganography. We also present some technical details of the techniques and software for applying steganography, including some security-related attack issues. Our article concludes with a presentation of some key topics for the reader’s consideration.