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 Mathematics , 2014, Abstract: Encryption prevents unauthorized decoding, but does not ensure stealth---a security demand that a mere presence of a message be undetectable. We characterize the ultimate limit of covert communication that is secure against the most powerful physically-permissible adversary. We show that, although it is impossible over a pure-loss channel, covert communication is attainable in the presence of any excess noise, such as a $300$K thermal blackbody. In this case, $\mathcal{O}(\sqrt{n})$ bits can be transmitted reliably and covertly in $n$ optical modes using standard optical communication equipment. The all-powerful adversary may intercept all transmitted photons not received by the intended receiver, and employ arbitrary quantum memory and measurements. Conversely, we show that this square root scaling cannot be outperformed. We corroborate our theory in a proof-of-concept experiment. We believe that our findings will enable practical realizations of covert communication and sensing, both for point-to-point and networked scenarios.
 Yinpu Zhang Journal of Networks , 2012, DOI: 10.4304/jnw.7.4.730-737 Abstract: Based on the security of information transmission through network in the information society, the paper puts forward covert communication technology which is more reliable than the prior encryption algorithm, analyzes channel covertness and information hiding of covert communication technology based on spread-spectrum communication technology, and establishes a covert communication system including image steganalysis, Arnold transformation and scrambling of carrier image, embedding of secret information, generation of encrypted image and recovering of carrier image by image-based covert communication technology. The simulation result shows: in order to ensure there is no serious degrading problem after embedding the secret information, the carrier image must have a large capacity; the larger the scrambling times is, the better the scrambling and encrypting effect is. Therefore, the airspace covert communication algorithm based on spread-spectrum communication technology well achieves safe transmission of information and has good application prospect.
 Computer Science , 2013, Abstract: In the last decade, there has been a growing realization that the current Internet Protocol is reaching the limits of its senescence. This has prompted several research efforts that aim to design potential next-generation Internet architectures. Named Data Networking (NDN), an instantiation of the content-centric approach to networking, is one such effort. In contrast with IP, NDN routers maintain a significant amount of user-driven state. In this paper we investigate how to use this state for covert ephemeral communication (CEC). CEC allows two or more parties to covertly exchange ephemeral messages, i.e., messages that become unavailable after a certain amount of time. Our techniques rely only on network-layer, rather than application-layer, services. This makes our protocols robust, and communication difficult to uncover. We show that users can build high-bandwidth CECs exploiting features unique to NDN: in-network caches, routers' forwarding state and name matching rules. We assess feasibility and performance of proposed cover channels using a local setup and the official NDN testbed.
 Mathematics , 2015, Abstract: Widely-deployed encryption-based security prevents unauthorized decoding, but does not ensure undetectability of communication. However, covert, or low probability of detection/intercept (LPD/LPI) communication is crucial in many scenarios ranging from covert military operations and the organization of social unrest, to privacy protection for users of wireless networks. In addition, encrypted data or even just the transmission of a signal can arouse suspicion, and even the most theoretically robust encryption can often be defeated by a determined adversary using non-computational methods such as side-channel analysis. Various covert communication techniques were developed to address these concerns, including steganography for finite-alphabet noiseless applications and spread-spectrum systems for wireless communications. After reviewing these covert communication systems, this article discusses new results on the fundamental limits of their capabilities, as well as provides a vision for the future of such systems.
 Joshua Davis Computer Science , 2014, Abstract: A covert communication system is developed that modulates Morse code characteristics and that delivers its mes- sage economically and to geographically remote areas using radio and EchoLink. Our system allows a covert message to be sent to a receiving individual by hiding it in an existing carrier Morse code message. The carrier need not be sent directly to the receiving person, though the receiver must have access to the signal. Illustratively, we propose that our system may be used as an alternative means of implementing numbers stations.
 计算机应用研究 , 2010, Abstract: The paper presented a covert communication method based on program slicing.Found the relationship between an arbitrary 0,1 string and code. In addition to this,proposed a covert communication model and discussed an algorithm in detail. The method is imperceptibility and anti-extractable.
 Computer Science , 2015, Abstract: Covert channels is a vital setup in the analysing the strength of security in a network.Covert Channel is illegitimate channelling over the secured channel and establishes a malicious conversation.The trapdoor set in such channels proliferates making covert channel sophisticated to detect their presence in network firewall.This is due to the intricate covert scheme that enables to build robust covert channel over the network.From an attacker's perspective this will ameliorate by placing multiple such trapdoors in different protocols in the rudimentary protocol stack. This leads to a unique scenario of Hybrid Covert Channel, where different covert channel trapdoors exist at the same instance of time in same layer of protocol stack. For detection agents to detect such event is complicated due to lack of knowledge over the different covert schemes. To improve the knowledge of the detection engine to detect the hybrid covert channel scenario it is required to explore all possible clandestine mediums used in the formation of such channels. This can be explored by different schemes available and their entropy impact on hybrid covert channel. The environment can be composed of resources and subject under at-tack and subject which have initiated the attack (attacker). The paper sets itself an objective to understand the different covert schemes and the attack scenario (modelling) and possibilities of covert mediums along with metric for detection.
 计算机科学 , 2009, Abstract: Secret communication is to hide the existence of communication.This work relates network security and privacy with data hiding techniques,focusing on secret communication using covert channels in network traffic.The framework,classification and evaluation of covert channels and design issues in secret communication protocols were investigated.Covert channels were divided into structure-mode,behavior-mode and content-mode.The comparison of different channels illustrates that channels in structure-mode and be...
 计算机应用研究 , 2012, Abstract: To solve the problem that the existing IP covert timing channel tools can not communicate with each other due to the lack of uniform protocol constraint, based on the OSI/RM, this paper established four layer protocol model of IP covert timing channel and gave the specific design. Furthermore, implemented a practical IP covert timing channel software which meeting the requirements of the hierarchical communication protocol.
 Physics , 2015, Abstract: In this work we implement a graph theoretical realization of local unitary transformations, implemented by single qubit Pauli gates, by adapting techniques of graph switching. This leads to the concept of local unitary equivalent graphs. We illustrate our method by a few, well known, local unitary transformations implemented by single qubit Pauli and Hadamard gates.
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