Communication and Secrecy: Issues in Digital Stenography

We present the issues involved in information obfuscation both for the embedding of information within digital signals and the detection of the hidden information. More standard cryptographic techniques acheive security through an encoding so that an evesdropper is unable to understand the signal. Obfuscation, preceded by an encoding, provides a method for the embedding of information within other signals so that an evesdropper is unable to detect the original information. A framework, based on information theory, is presented that ensures embedded signals are undetectable under a set of conditions called the Grammatic Invariance Principle. An algorithm for embedding information within digital images (a technique often referred to as stenography) is developed under the framework and results are presented.