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arXiv 1801.08154cs.CR
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通用隐写术安全性的金标准

On the Gold Standard for Security of Universal Steganography

Sebastian Berndt, Maciej Liśkiewicz

摘要:

虽然公钥隐写术在信息论和计算环境中都得到了很好的理解,但关于公钥隐写术的许多基本问题却一直没有得到解决。公开密钥隐写术的计算模型是由von Ahn和Hopper在EUROPHOTOPT 2004中提出的。在TCC 2005上,Backes和Cachin给出了第一个通用的公钥隐写系统-即在所有信道上工作的系统-实现了对可重放的选择覆盖文本攻击(SS-RCCA)的安全性,并询问是否可以实现对不可重放的选择覆盖文本攻击(SS-CCA)的安全性。后来,Hopper(ICALP 2005)为每个有效采样通道提供了这样的隐写系统,但没有实现普遍性。他提出了能否同时实现普遍性和安全保障共同国家评估安全的问题。十多年来,在这个问题上没有取得任何进展。在我们的工作中,我们以某种完整的方式解决了Hopper的问题:作为我们的主要积极成果,我们设计了一个SS-CCA安全的隐写系统,适用于每个无记忆信道。另一方面,我们证明了这一结果是最好的通用隐写术的背景下。我们提供了一个家庭的0-无记忆通道-已经发送的文件只有边际影响当前的分布-并证明没有SS-CCA安全隐写术,这个家庭存在于标准的非前瞻性模型。

英文摘要:

While symmetric-key steganography is quite well understood both in the information-theoretic and in the computational setting, many fundamental questions about its public-key counterpart resist persistent attempts to solve them. The computational model for public-key steganography was proposed by von Ahn and Hopper in EUROCRYPT 2004. At TCC 2005, Backes and Cachin gave the first universal public-key stegosystem - i.e. one that works on all channels - achieving security against replayable chosen-covertext attacks (SS-RCCA) and asked whether security against non-replayable chosen-covertext attacks (SS-CCA) is achievable. Later, Hopper (ICALP 2005) provided such a stegosystem for every efficiently sampleable channel, but did not achieve universality. He posed the question whether universality and SS-CCA-security can be achieved simultaneously. No progress on this question has been achieved since more than a decade. In our work we solve Hopper's problem in a somehow complete manner: As our main positive result we design an SS-CCA-secure stegosystem that works for every memoryless channel. On the other hand, we prove that this result is the best possible in the context of universal steganography. We provide a family of 0-memoryless channels - where the already sent documents have only marginal influence on the current distribution - and prove that no SS-CCA-secure steganography for this family exists in the standard non-look-ahead model.

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