標題:Toward a Theory of Steganography

Informally, steganography refers to the practice of hiding secret messages in communications over a public channel so that an eavesdropper (who listens to all communications) cannot even tell that a secret message is being sent. In contrast to the active literature proposing new concrete steganographic protocols and analysing flaws in existing protocols, there has been very little work on formalizing steganographic notions of security, and none giving complete, rigorous proofs of security in a satisfying model.

This thesis initiates the study of steganography from a cryptographic point of view. We give a precise model of a communication channel and a rigorous definition of steganographic security, and prove that relative to a channel oracle, secure steganography exists if and only if one-way functions exist. We give tightly matching upper and lower bounds on the maximum rate of any secure stegosystem. We introduce the concept of steganographic key exchange and public-key steganography, and show that provably secure protocols for these objectives exist under a variety of standard number-theoretic assumptions. We consider several notions of active attacks against steganography, show how to achieve each under standard assumptions, and consider the relationships between these notions. Finally, we extend the concept of steganograpy as covert communication to include the more general concept of covert computation.

作者:Nicholas J. Hopper


摘要(英翻中):
我們給通訊電路的一個精確模型和steganographic安全一個嚴謹定義，並且證明相對於渠道oracle安全steganography的存在當單程作用存在時。我們給所有安全stegosystem的最高率的上限和下限。
我們介紹steganographic關鍵交換和公眾鑰匙steganography的概念，並且表示可證明這些宗旨的安全協議存在於各種各樣的標準數字理論假定外。
我們考慮幾個活躍攻擊反對steganography的概念，顯示如何達到其中每一個在標準假定外，並且考慮這些概念之間的關係。
終於，我們擴大steganograpy的概唸作為隱蔽通信包括隱蔽計算的普通概念。