Current wireless communications are confronted with two significant problems with regard to spectrum use --- spectrum scarcity and deployment difficulties. It is widely believed that Software Defined Radios (SDRs) and Cognitive Radios (CRs) are the key enabling technologies to address these problems. The reconfigurability of SDRs combined with the decoupling of policies and the platform in policy-based radios poses a new technical problem --- viz, enforcing policy conformance. Each DARPA XG radio is equipped with a set of policy conformance components (PCCs) which are responsible for ensuring that the radio is policy-conformant and does not cause harmful interference. The Policy Reasoner (PR) is the inference component of the PCCs whereas the Policy Enforcer (PE) performs enforcement. DARPA's XG program prescribes the Software Communications Architecture (SCA) as the model for SDR/CR architectures. Distributed processing is a fundamental aspect of the SCA, and it uses the Common Object Resource Broker Architecture (CORBA). It is reasonable to assume that some of the SDRs will be implemented as distributed systems, irrelevant of whether they are SCA compliant devices. It is thus obvious that middleware has to be secured for complete security. This thesis enumerates the requirements of an "ideal" PE. We have described the design and implementation of two possible implementations, which can fulfill some of these requirements. The PE can function similar to a firewall, and be at the very boundary of software and hardware components. The PE can also be implemented as a "man-in-the-middle" between the System Strategy Reasoner and the transmission hardware. We further describe a novel method of providing cache coherency for a cache-based PE. We also perform an in-depth analysis of the security requirements in a distributed implementation of a policy-based radio. To this end, we describe the design and implementation of such a system using CORBA middleware. We identify potential vulnerabilities due to the use of CORBA, and describe countermeasures for them. We compare the performance of transport and security mechanisms of two commercial, off-the-shelf (COTS) Object Request Brokers. We show that the magnitude of performance degradation can be reduced by the use of a cleverly selected combination of transport and security mechanisms. / Master of Science

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Fighting has been a centerpiece of the National Hockey League since it was formed in 1917. Although rules have been introduced regulating the physicality of play in the NHL, fighting is demanded—and encouraged—by fans and players alike. Fans have long been attracted to the violence of professional hockey; previous studies have documented that professional hockey is a “blood sport” that generates revenues with violence. This research investigates the effect of fighting on player salaries in the NHL, examining the way in which fighting has become a strategic element of the game, describing the way players enforce their own “Code” of hockey rules and police the ice in ways referees cannot, and comparing the salaries of fighters and skilled players to determine how players in different roles are valued.

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<p>\section*{Abstract}<br />We study Maker-Breaker games played on the edges of the complete graph on $n$ vertices, $K_n$, whose family of winning sets $\cF$ consists of all edge sets of subgraphs $G\subseteq K_n$ which possess a predetermined monotone increasing property. Two players, Maker and Breaker, take turns in claiming $a$, respectively $b$, unclaimed edges per move. We are interested in finding the threshold bias $b_{\cF}(a)$ for all values of $a$, so that for every $b$, $b\leq b_{\cF}(a)$, Maker wins the game and for all values of $b$, such that $b&gt;b_{\cF}(a)$, Breaker wins the game. We are particularly interested in cases where both $a$ and $b$ can be greater than $1$. We focus on the \textit{Connectivity game}, where the winning sets are the edge sets of all spanning trees of $K_n$ and on the&nbsp; \textit{Hamiltonicity game}, where the winning sets are the edge sets of all Hamilton cycles on $K_n$.<br /><br />Next, we consider biased $(1:b)$ Avoider-Enforcer games, also played on the edges of $K_n$. For every constant $k\geq 3$ we analyse the $k$-star game, where Avoider tries<br />to avoid claiming $k$ edges incident to the same vertex. We analyse both versions of Avoider-Enforcer games, the strict and the monotone, and for each provide explicit winning strategies for both players. Consequentially, we establish bounds on the threshold biases $f^{mon}_\cF$, $f^-_\cF$ and $f^+_\cF$, where $\cF$ is the hypergraph of the game (the family of target sets).<br />We also study the monotone version of $K_{2,2}$-game, where Avoider wants to avoid claiming all the edges of some graph isomorphic to $K_{2,2}$ in $K_n$.&nbsp;&nbsp;</p><p>Finally, we search for the fast winning strategies for Maker in Perfect matching game and Hamiltonicity game, again played on the edge set of $K_n$. Here, we look at the biased $(1:b)$ games, where Maker&#39;s bias is 1, and Breaker&#39;s bias is $b, b\ge 1$.</p> / <p>\section*{Izvod}</p><p>Prou\v{c}avamo takozvane Mejker-Brejker (Maker-Breaker) igre koje se igraju na granama kompletnog grafa sa $n$ \v{c}vorova, $K_n$, \v{c}ija familija pobedni\v{c}kih skupova $\cF$ obuhvata sve skupove grana grafa $G\subseteq K_n$ koji imaju neku monotono rastu\&#39;{c}u osobinu. Dva igra\v{c}a, \textit{Mejker} (\textit{Pravi\v{s}a}) i \textit{Brejker} (\textit{Kva\-ri\-\v{s}a}) se smenjuju u odabiru $a$, odnosno $b$, slobodnih grana po potezu. Interesuje nas da prona\dj emo grani\v{c}ni bias $b_{\cF}(a)$ za sve vrednosti pa\-ra\-me\-tra $a$, tako da za svako $b$, $b\le b_{\cF}(a)$, Mejker pobe\dj uje u igri, a za svako $b$, takvo da je $b&gt;b_{\cF}(a)$, Brejker pobe\dj uje. Posebno nas interesuju slu\v{c}ajevi u kojima oba parametra $a$ i $b$ mogu imati vrednost ve\&#39;cu od 1. Na\v{s}a pa\v{z}nja je posve\&#39;{c}ena igri povezanosti, gde su pobedni\v{c}ki skupovi&nbsp; grane svih pokrivaju\&#39;cih stabala grafa $K_n$, kao i igri Hamiltonove konture, gde su pobedni\v{c}ki skupovi grane svih Hamiltonovih kontura grafa $K_n$.</p><p>Zatim posmatramo igre tipa Avojder-Enforser (Avoider-Enforcer), sa biasom $(1:b)$, koje se tako\dj e igraju na granama kompletnog grafa sa $n$ \v{c}vorova, $K_n$. Za svaku konstantu $k$, $k\ge 3$ analiziramo igru $k$-zvezde (zvezde sa $k$ krakova), u kojoj \textit{Avojder} poku\v{s}va da izbegne da ima $k$ svojih grana incidentnih sa istim \v{c}vorom. Posmatramo obe verzije ove igre, striktnu i monotonu, i za svaku dajemo eksplicitnu pobedni\v{c}ku strategiju za oba igra\v{c}a. Kao rezultat, dobijamo gornje i donje ograni\v{c}enje za grani\v{c}ne biase $f^{mon}_\cF$, $f^-_\cF$ i $f^+_\cF$, gde $\cF$ predstavlja hipergraf igre (familija ciljnih skupova).<br />%$f^{mon}$, $f^-$ and $f^+$.<br />Tako\dj e, posmatramo i monotonu verziju $K_{2,2}$-igre, gde Avojder \v{z}eli da izbegne da graf koji \v{c}ine njegove grane sadr\v{z}i graf izomorfan sa $K_{2,2}$.</p><p>Kona\v{c}no, \v{z}elimo da prona\dj emo strategije za brzu pobedu Mejkera u igrama savr\v{s}enog me\v{c}inga i Hamiltonove konture, koje se tako\dj e igraju na granama kompletnog grafa $K_n$. Ovde posmatramo asimetri\v{c}ne igre gde je bias Mejkera 1, a bias Brejkera $b$, $b\ge 1$.</p>

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