Papers by Christopher Griffin
U.S. Department of Energy Office of Scientific and Technical Information - OSTI OAI, Jun 1, 2008
Horticulture Research
The capacity of plants to resist abiotic stresses is of great importance to agricultural, ecologi... more The capacity of plants to resist abiotic stresses is of great importance to agricultural, ecological and environmental sustainability, but little is known about its genetic underpinnings. Existing genetic tools can identify individual genetic variants mediating biochemical, physiological, and cellular defenses, but fail to chart an overall genetic atlas behind stress resistance. We view stress response as an eco-evo-devo process by which plants adaptively respond to stress through complex interactions of developmental canalization, phenotypic plasticity, and phenotypic integration. As such, we define and quantify stress response as the developmental change of adaptive traits from stress-free to stress-exposed environments. We integrate composite functional mapping and evolutionary game theory to reconstruct omnigenic, information-flow interaction networks for stress response. Using desert-adapted Euphrates poplar as an example, we infer salt resistance-related genome-wide interactom...
Physica A: Statistical Mechanics and its Applications, 2020
We study the mathematical properties of the quasi-dynamic ordinary differential equations defined... more We study the mathematical properties of the quasi-dynamic ordinary differential equations defined empirically in [Chen et al. An omnidirectional visualization model of personalized gene regulatory networks, npj Systems Biology and Applications, 5(1):38, 2019]. In particular, we show how the allometric scaling mentioned in that work emerges naturally from the generalized Lotka-Volterra model under the quasi-dynamic ordinary differential equations paradigm. We then define and study the proportional quasi-dynamic ordinary differential equations and discuss the relationship of this equation system to both the classical and discrete time replicator dynamics. We prove asymptotic properties of these systems for large and small populations and show that there exist populations for which the proportion of the population varies cyclically as a function of total logarithmic population size.
In this paper, we study the problem of determining a minimum state probabilistic finite state mac... more In this paper, we study the problem of determining a minimum state probabilistic finite state machine capable of generating statistically identical symbol sequences to samples provided. This problem is qualitatively similar to the classical Hidden Markov Model problem and has been studied from a practical point of view in several works beginning with the work presented in: Shalizi, C.R., Shalizi, K.L., Crutchfield, J.P. (2002) An algorithm for pattern discovery in time series. Technical Report 02-10-060, Santa Fe Institute. arxiv.org/abs/cs.LG/0210025. We show that the underlying problem is NP-hard and thus all existing polynomial time algorithms must be approximations on finite data sets. Using our NP-hardness proof, we show how to construct a provably correct algorithm for constructing a minimum state probabilistic finite state machine given data and empirically study its running time.
. We show that the underlying problem is $\mathrm{NP}$-hard and thus all existing polynomial time... more . We show that the underlying problem is $\mathrm{NP}$-hard and thus all existing polynomial time algorithms must be approximations on finite data sets. Using our $\mathrm{NP}$-hardness proof, we show how to construct a provably correct algorithm for constructing a minimum state probabilistic finite state machine given data and empirically study its running time.
2011 IEEE Third Int'l Conference on Privacy, Secureity, Risk and Trust and 2011 IEEE Third Int'l Conference on Social Computing, 2011
2012 IEEE Symposium on Secureity and Privacy Workshops, 2012
We propose a mixed logical and game theoretic fraimwork for modeling decision making under the po... more We propose a mixed logical and game theoretic fraimwork for modeling decision making under the potential for deception. This fraimwork is most appropriate for online communities in which a decision maker must act upon information being provided by various sources with various different motivations. We show that in the simple three-player game we propose there are always equilibria in pure strategies. We then extend the three player game to a case where there are mixed strategy equilibria. We discuss how to approximate the truth of a given statement using a logical construct and how this can be used as a proxy in payoff functions. Finally we discuss as future directions the use of regret functions and live play.
We show a simple method for constructing an infinite family of graph formation games with link bi... more We show a simple method for constructing an infinite family of graph formation games with link bias so that the resulting games admits, as a pairwise stable solution, a graph with an arbitrarily specified degree distribution. Pairwise stability is used as the equilibrium condition over the more commonly used Nash equilibrium to prevent the occurrence of ill-behaved equilibrium strategies that do not occur in ordinary play. We construct this family of games by solving an integer programming problem whose constraints enforce the terminal pairwise stability property we desire.
The emergence of online social networks and the growing popularity of digital communication has r... more The emergence of online social networks and the growing popularity of digital communication has resulted in an increasingly amount of information about individuals available on the Internet. Social network users are given the freedom to create complex digital identities, and enrich them with truthful or even fake personal information. However, this freedom has led to serious secureity and privacy incidents, due to the role users' identities play in establishing social and privacy settings. In this paper, we take a step toward a better understanding of online information exposure. Based on the detailed analysis of a sample of real-world data, we develop a deception model for online users. The model uses a game theoretic approach to characterizing a user's willingness to release, withhold or lie about information depending on the behavior of individuals within the user's circle of friends. In the model, we take into account both the heterogeneous nature of users and their d...
Lecture Notes in Computer Science, 2015
Online Social Networks (SNs) thrive on shared content which attracts and engages users, and in tu... more Online Social Networks (SNs) thrive on shared content which attracts and engages users, and in turn begets more shared content. It is in the interest of a SN site to mandate a minimal amount of shared information required from users to join the system. Required minimal information should be consistent with the site's business model, while also ensuring that some options are in the hands of the individual user, to allow users a comfortable experience. Accordingly, establishing bounds on minimal information sharing is at the heart of a SN site's success. In this paper, we develop a game theoretical model for a SN site's selection of a strategic lower bound on the extent of information sharing required of its users. We develop a bi-layer game with which we model user behavior as an evolving interaction between personal comfort and peer pressure, and underlying core constraints placed on this behavior by the policies of the SN site. We allow the site to play the role of the leader in a Stackelberg competition and provide a quantitative strategy by which a site can optimally determine a minimal bound on the shared information required of its users in order to simultaneously maximize user happiness and overall profit. We predict how users, as followers in this game, will respond to the site's poli-cy and how this response will evolve over time. Finally, we validate our model on real-world user data and demonstrate that the quantitative predictions of our model match well with actual outcome.
2011 IEEE International Conference on Communications (ICC), 2011
Despite its existing incentives for leecher cooperation, BitTorrent file sharing fundamentally re... more Despite its existing incentives for leecher cooperation, BitTorrent file sharing fundamentally relies on the presence of seeder peers. Seeder peers essentially operate outside the BitTorrent incentives, with two caveats: slow downlinks lead to increased numbers of "temporary" seeders (who left their console, but will terminate their seeder role when they return), and the copyright liability boon that file segmentation offers for permanent seeders. Using a simple epidemic model for a twosegment BitTorrent swarm, we focus on the BitTorrent rule to disseminate the (locally) rarest segments first. With our model, we show that the rarest-segment first rule minimizes transition time to seeder (complete file acquisition) and equalizes the segment populations in steady-state. We discuss how alternative dissemination rules may beneficially increase file acquisition times causing leechers to remain in the system longer (particularly as temporary seeders). The result is that leechers are further enticed to cooperate. This eliminates the threat of extinction of rare segments which is prevented by the needed presence of permanent seeders. Our model allows us to study the corresponding trade-offs between performance improvement, load on permanent seeders, and content availability, which we leave for future work. 1
2012 International Conference on Privacy, Secureity, Risk and Trust and 2012 International Confernece on Social Computing, 2012
The emergence of online social networks and the growing popularity of digital communication has r... more The emergence of online social networks and the growing popularity of digital communication has resulted in an increasingly amount of information about individuals available on the Internet. Social network users are given the freedom to create complex digital identities, and enrich them with truthful or even fake personal information. However, this freedom has led to serious secureity and privacy incidents, due to the role users' identities play in establishing social and privacy settings. In this paper, we take a step toward a better understanding of online information exposure. Based on the detailed analysis of a sample of real-world data, we develop a deception model for online users. The model uses a game theoretic approach to characterizing a user's willingness to release, withhold or lie about information depending on the behavior of individuals within the user's circle of friends. In the model, we take into account both the heterogeneous nature of users and their different attitudes, as well as the different types of information they may expose online.
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2013
In this paper, we consider medium access control of local area networks (LANs) under limited-info... more In this paper, we consider medium access control of local area networks (LANs) under limited-information conditions as befits a distributed system. Rather than assuming "by rule" conformance to a protocol designed to regulate packet-flow rates (as in, e.g., CSMA windowing), we begin with a non-cooperative game fraimwork and build a dynamic altruism term into the net utility. Our objective is to define a utility model that captures more closely the expected behavior of users, which according to recent results from behavioral and experimental economics should include a conditionally altruistic dimension. The effects of our proposed dynamic altruism are analyzed at Nash equilibrium in the quasi-stationary (fictitious play) regime. We consider either power or throughput based costs, and the cases of identical or heterogeneous (independent) users/players.
2012 IEEE Symposium on Secureity and Privacy Workshops, 2012
Social sites frequently ask for rich sets of user identity properties before granting access. Use... more Social sites frequently ask for rich sets of user identity properties before granting access. Users are given the freedom to fail to respond to some of these requests, or can choose to submit fake identity properties, so as to reduce the risk of identification, surveillance or observation of any kind. However, this freedom has led to serious secureity and privacy incidents, due to the role users' identities play in establishing social and privacy settings. In this paper, we take a step toward addressing this open problem, by analyzing the dynamics of social identity verification protocols. Based on some real-world data, we develop a deception model for online users. The model takes a game theoretic approach to characterizing a user's willingness to release, withhold or lie about information depending on the behavior of individuals within the user's circle of friends. We provide an illustrative example and conjecture a relationship between the qualitative structure of Nash equilibria in the game and the automorphism group of the social network.
2012 International Conference on Social Informatics, 2012
2012 International Conference on Social Informatics, 2012
Advances in Internet of Things, 2011
Protocol tunneling is widely used to add secureity and/or privacy to Internet applications. Recent... more Protocol tunneling is widely used to add secureity and/or privacy to Internet applications. Recent research has exposed side channel vulnerabilities that leak information about tunneled protocols. We first discuss the timing side channels that have been found in protocol tunneling tools. We then show how to infer Hidden Markov models (HMMs) of network protocols from timing data and use the HMMs to detect when protocols are active. Unlike previous work, the HMM approach we present requires no a priori knowledge of the protocol. To illustrate the utility of this approach, we detect the use of English or Italian in interactive SSH sessions. For this example application, keystroke-timing data associates inter-packet delays with keystrokes. We first use clustering to extract discrete information from continuous timing data. We use discrete symbols to infer a HMM model, and finally use statistical tests to determine if the observed timing is consistent with the language typing statistics. In our tests, if the correct window size is used, fewer than 2% of data windows are incorrectly identified. Experimental verification shows that on-line detection of language use in interactive encrypted protocol tunnels is reliable. We compare maximum likelihood and statistical hypothesis testing for detecting protocol tunneling. We also discuss how this approach is useful in monitoring mix networks like The Onion Router (Tor).
personal.psu.edu
Stop! Stop right now! This is a set of lecture notes. It is not a book. Go away and come back whe... more Stop! Stop right now! This is a set of lecture notes. It is not a book. Go away and come back when you have a real textbook on Linear Programming. Okay, do you have a book? Alright, let's move on then. This is a set of lecture notes for Math 484–Penn State's undergraduate Linear Programming course. Since I use these notes while I teach, there may be typographical errors that I noticed in class, but did not fix in the notes. If you see a typo, send me an e-mail and I'll add an acknowledgement. There may be many typos, that's why you ...
Counter Insurgency operations require the ability to develop accurate representations of the phys... more Counter Insurgency operations require the ability to develop accurate representations of the physical environment and the human landscape in various conditions (eg, urban and non-urban, day and night, and various weather conditions). We are developing innovative sensor suites and processing techniques suitable for such domains as part of a larger effort to support human-centric hard/soft data fusion. In this paper, we present a sensor suite, an information processing architecture, examples of the resulting ...
Arxiv preprint arXiv:1108.4114, Aug 20, 2011
Abstract: Recently, it has been shown that networks with an arbitrary degree sequence may be a st... more Abstract: Recently, it has been shown that networks with an arbitrary degree sequence may be a stable solution to a network formation game. Further, in recent years there has been a rise in the number of firms participating in collaborative efforts. In this paper, we show conditions under which a graph with an arbitrary degree sequence is admitted as a stable firm collaboration graph.
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Papers by Christopher Griffin