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1. A Cooperative Jamming Game in Wireless Networks under Uncertainty

   https://doi.org/10.1007/978-3-030-63086-7_14  

   Xu, Z.; Baykal-Gürsoy, M. (December 2020, Security and Privacy in Communication Networks. SecureComm 2020. Lecture Notes)

   null (Ed.)

   Considered is a multi-channel wireless network for secret communication that uses the signal-to-interference-plus-noise ratio (SINR) as the performance measure. An eavesdropper can intercept encoded messages through a degraded channel of each legitimate transmitter-receiver communication pair. A friendly interferer, on the other hand, may send cooperative jamming signals to enhance the secrecy performance of the whole network. Besides, the state information of the eavesdropping channel may not be known completely. The transmitters and the friendly interferer have to cooperatively decide on the optimal jamming power allocation strategy that balances the secrecy performance with the cost of employing intentional interference, while the eavesdropper tries to maximize her eavesdropping capacity. To solve this problem, we propose and analyze a non-zero-sum game between the network defender and the eavesdropper who can only attack a limited number of channels. We show that the Nash equilibrium strategies for the players are of threshold type. We present an algorithm to find the equilibrium strategy pair. Numerical examples demonstrate the equilibrium and contrast it to baseline strategies. 

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2. A Friendly Interference Game in Wireless Secret Communication Networks

   https://doi.org/https://doi.org/10.1007/978-3-030-87473-5_4  

   Xu, Z.; Baykal-Gürsoy, M. (September 2021, 10th International Conference on NETwork Games, COntrol and OPtimization (NetGCOOP))

   Filipe, J.; Ghosh, A.; Prates, R. O.; Zhou, L. (Ed.)

   This paper considers a parallel wireless network in which multiple individuals exchange confidential information through independent sender-receiver links. An eavesdropper can intercept encrypted information through a degraded channel of each sender-receiver link. A friendly jammer, by applying interference to the eavesdropping channels, can increase the level of secrecy of the network. The optimal power allocation strategy of the friendly jammer under a power constraint is derived. A convex optimization model is used when all channels are under the threat of an eavesdropping attack and a non-zero sum game model is analyzed when the eavesdropper can only attack a limited quantity of channels. 

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3. Secure Degrees of Freedom in Networks with User Misbehavior

   https://doi.org/10.3390/e21100945  

   Banawan, Karim; Ulukus, Sennur (October 2019, Entropy)

   We investigate the secure degrees of freedom (s.d.o.f.) of three new channel models: broadcast channel with combating helpers, interference channel with selfish users, and multiple access wiretap channel with deviating users. The goal of introducing these channel models is to investigate various malicious interactions that arise in networks, including active adversaries. That is in contrast with the common assumption in the literature that the users follow a certain protocol altruistically and transmit both message-carrying and cooperative jamming signals in an optimum manner. In the first model, over a classical broadcast channel with confidential messages (BCCM), there are two helpers, each associated with one of the receivers. In the second model, over a classical interference channel with confidential messages (ICCM), there is a helper and users are selfish. By casting each problem as an extensive-form game and applying recursive real interference alignment, we show that, for the first model, the combating intentions of the helpers are neutralized and the full s.d.o.f. is retained; for the second model, selfishness precludes secure communication and no s.d.o.f. is achieved. In the third model, we consider the multiple access wiretap channel (MAC-WTC), where multiple legitimate users wish to have secure communication with a legitimate receiver in the presence of an eavesdropper. We consider the case when a subset of users deviate from the optimum protocol that attains the exact s.d.o.f. of this channel. We consider two kinds of deviation: when some of the users stop transmitting cooperative jamming signals, and when a user starts sending intentional jamming signals. For the first scenario, we investigate possible responses of the remaining users to counteract such deviation. For the second scenario, we use an extensive-form game formulation for the interactions of the deviating and well-behaving users. We prove that a deviating user can drive the s.d.o.f. to zero; however, the remaining users can exploit its intentional jamming signals as cooperative jamming signals against the eavesdropper and achieve an optimum s.d.o.f. 

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4. Cost-Efficient Network Protection Games Against Uncertain Types of Cyber-Attackers

   https://doi.org/10.1109/HST56032.2022.10025437  

   Xu, Zhifan; Baykal-Gursoy, Melike (November 2022, 2022 IEEE International Symposium on Technologies for Homeland Security (HST))

   This paper considers network protection games for a heterogeneous network system with N nodes against cyber-attackers of two different types of intentions. The first type tries to maximize damage based on the value of each net-worked node, while the second type only aims at successful infiltration. A defender, by applying defensive resources to networked nodes, can decrease those nodes' vulnerabilities. Meanwhile, the defender needs to balance the cost of using defensive resources and potential security benefits. Existing literature shows that, in a Nash equilibrium, the defender should adopt different resource allocation strategies against different types of attackers. However, it could be difficult for the defender to know the type of incoming cyber-attackers. A Bayesian game is investigated considering the case that the defender is uncertain about the attacker's type. We demonstrate that the Bayesian equilibrium defensive resource allocation strategy is a mixture of the Nash equilibrium strategies from the games against the two types of attackers separately. 

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5. Secret key distillation over a pure loss quantum wiretap channel under restricted eavesdropping

   https://doi.org/10.1109/ISIT.2019.8849223  

   Pan, Ziwen; Seshadreesan, Kaushik P.; Clark, William; Adcock, Mark R.; Djordjevic, Ivan B.; Shapiro, Jeffrey H.; Guha, Saikat (July 2019, 2019 IEEE International Symposium on Information Theory (ISIT))

   Quantum cryptography provides absolute security against an all-powerful eavesdropper (Eve). However, in practice Eve's resources may be restricted to a limited aperture size so that she cannot collect all paraxial light without alerting the communicating parties (Alice and Bob). In this paper we study a quantum wiretap channel in which the connection from Alice to Eve is lossy, so that some of the transmitted quantum information is inaccessible to both Bob and Eve. For a pureloss channel under such restricted eavesdropping, we show that the key rates achievable with a two-mode squeezed vacuum state, heterodyne detection, and public classical communication assistance-given by the Hashing inequality-can exceed the secret key distillation capacity of the channel against an omnipotent eavesdropper. We report upper bounds on the key rates under the restricted eavesdropping model based on the relative entropy of entanglement, which closely match the achievable rates. For the pure-loss channel under restricted eavesdropping, we compare the secret-key rates of continuous-variable (CV) quantum key distribution (QKD) based on Gaussian-modulated coherent states and heterodyne detection with the discrete variable (DV) decoystate BB84 QKD protocol based on polarization qubits encoded in weak coherent laser pulses. 

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