M.S.

The immutability, validity and confidentiality of an audit log is crucial when operating over sensitive data to comply to standard data regulations (e.g., HIPAA). Despite its critical needs, state-of-the-art privacy-preserving audit log schemes (e.g., Ghostor (NSDI '20), Calypso (VLDB '19)) do not fully obtain a high level of privacy, integrity, and immutability simultaneously, in which certain information (e.g., user identities) is still leaked in the log. In this work, we propose Harpocrates, a new privacy-preserving and immutable audit log scheme. Harpocrates permits data store, share, and access operations to be recorded in the audit log without leaking sensitive information (e.g., data identifier, user identity), while permitting the validity of data operations to be publicly verifiable. Harpocrates makes use of blockchain techniques to achieve immutability and avoid a single point of failure, while cryptographic zero-knowledge proofs are harnessed for confidentiality and public verifiability. We analyze the security of our proposed technique and prove that it achieves non-malleability and indistinguishability. We fully implemented Harpocrates and evaluated its performance on a real blockchain system (i.e., Hyperledger Fabric) deployed on a commodity platform (i.e., Amazon EC2). Experimental results demonstrated that Harpocrates is highly scalable and achieves practical performance. / Master of Science / Audit logs are an essential part of data storage systems as they allow to check if the system is working as intended. They are usually maintained on a server, a server with ill intentions can easily modify records of the log and make it appear that the system is working correctly. To store these records in an un-modifiable manner, prior works have leveraged special audit log storing mechanisms for e.g., blockchain due to its immutable nature. However, these works do not focus on the privacy of the records which is a crucial aspect for conforming to certain data regulations like HIPAA. In our work, we propose Harpocrates, an immutable and privacy-preserving audit log platform that supports recording operations (share/access) on sensitive data. Harpocrates leverages blockchain to achieve immutability of the audit log. Harpocrates use specific cryptographic primitives to achieve public verifiability and confidentiality of the audit log. Real world deployment of Harpocrates shows that it is practical and achieves strong security guarantees.

The Penn Virginia Resources Corporation is a large land holding company in southwest Virginia. Approximately 62 percent of their holdings are forested. The major objective of this study was to determine the economic feasibility of utilizing timber on Penn Virginia forest lands as a raw material for selected forest products. The study was conducted in three phases: (1) A market and resource analysis; (2) Estimation of the cost of harvesting and transporting timber from Penn Virginia lands to local processing facilities; and (3) An analysis of the economic feasibility of establishing new forest products markets utilizing Penn Virginia timber as the primary raw material supply. Results from phase one of the study indicated that approximately 116 wood-based industries are located within 50 miles of the Penn Virginia forest, and that the forest contains the resources to supply some of these existing markets. Phase two results were obtained using harvesting simulations. A harvesting system cutting conventional products and recovering residues was the most economical. A discounted cash flow analysis was employed in phase three of the study to examine the economic feasibility of establishing wood-based plants using Penn Virginia timber. Five mill types were analyzed: pallet mill, dimension mill, SHOLO mill, System 6 mill, and sawmill. Five sawmill configurations were examined. Results of this study phase indicated that the mill types showing the greatest potential for establishment using Fenn Virginia timber were the dimension mill, SHOLO mill, and scragg sawmill. All provided after-tax rates-of-return 0£ approximately 30 percent or higher. / Master of Science

A computerized system for planning timber harvest to maximize habitat quality over time for a specified group of wildlife species was developed for upland oak forests of the Eastern United States. This system, called WILDWOOD for WILDiife/WOOD optimization system, is designed to run on a microcomputer. It utilizes a widely available database management system called PCFile III, Version 4, a forest growth and yield simulator adapted from work by Dale (1972), and a program developed by the author. The system utilizes 43 species-specific habitat value models developed by the author and others. Timber harvests in approximately one ha blocks (patch clearcut) are specified for each year to result in a maximum yearly average wildlife benefit figure. Wildlife benefits are defined as the product of a wildlife species value provided by the user, a forest-size-classspecific habitat value index, and the area of the cutting unit. WILDWOOD was demonstrated on a 106 ha tract of upland oak forest on Havens Wildlife Management Area of the Virginia Commission of Game and Inland Fisheries. Six different objective functions were investigated and several model tests were conducted. Implications for the application of the WILDWOOD system were discussed, and it was concluded that, although the objectives of the study were met, the current WILDWOOD system should be modified to include smooth wildlife habitat succession models, at least a 150-year planning horizon, and capabilities for addressing cutting unit size, shape, and juxtaposition. Other possibilities for future revisions inclu~e modifying HEP (U.S. Fish and Wildlife Service) for use with WILDWOOD, and linking ageographic information system to WILDWOOD. / Master of Science

Twenty-four independent logging businesses in the Southeastern United States were analyzed in a general systems approach to document the components of logging costs for mechanized operations, assess the sensitivity of these components to external stimuli, and to identify and describe the business management techniques adopted by contractors to insure survival and profitability. The contractors' cost records for 1988 and 1989 were analyzed to meet the study's first two objectives and interviews with each participant facilitated identification of survival and profitability strategies. The general interviews and on-site observations of the harvesting systems provided background information for evaluating the costs and identifying business management techniques. The contractors' records were summarized into six cost components: 1) consumable supplies, 2) labor, 3) equipment,4) insurance. 5) contract hauling, and 6) administrative overhead. Contractors were stratified by trucking strategy, ranging from those who hauled all of their own wood to contractors relying exclusively on contract truckers. Consumable supplies, labor, and equipment accounted for approximately 75% of total costs for the average contractor in 1988 and 1989. The concept of excess logging capacity was evaluated. Analyses indicate that excess capacity exists in many areas of the Southeastern U.S., and excess capacity influences cost structures and survival strategies. Discussion with most contractors and evaluation of direct costs of excess capacity indicated that contractors are unable to achieve marginal efficiencies due to the large number of suppliers in some areas. Four major business survival strategies were identified during the study. Equity dissolution and diversification were the prevalent strategies, suggesting that the late 1980s and early 1990s favor harvesting systems that are downwardly elastic in terms of production. / Master of Science

Six wet pine flat sites were salvage logged following Hurricane Hugo in the fall of 1989. High soil moisture conditions during salvage operations resulted in soil compaction and deep rutting (puddling) on primary skid trails. Two studies were established to assess the effects of trafficking on soil physical properties and hydrologic characteristics. One addressed soil compaction; the other addressed soil rutting (puddling). Each study consisted of 3 sites (blocks) and trafficked and undisturbed areas were sampled on each site. Effects of trafficking on soil physical properties and hydrology were tested by comparing the disturbed (trafficked) and undisturbed subplots. Traffic increased bulk density and decreased soil porosity (macro-, micro-, total), water table levels, and saturated hydraulic conductivity within the compacted areas. However, the depth to reducing conditions was not significantly different from between undisturbed and disturbed areas of compacted sites. Puddling increased in bulk density and a decrease water table levels, depth of reducing conditions, soil porosity (macro-, micro-, and total), and saturated hydraulic conductivity (field and laboratory methods). Soil strength was not significantly different between disturbed and undisturbed areas. Overall, puddling resulted in soil changes that are more deleterious to tree growth than did compaction. Also puddling changes may prove more difficult to mitigate. / Master of Science

M. S.

The objective of this research was to design and test devices for addition to log trucks that removed mud from the dual-tires before the trucks entered the public road. The four devices built were simple, inexpensive, and could be built by a logging or trucking contractor. The "bar and scraper" and "mud flap" removed 85% and 84% of the mud, respectively, that adhered to the dual-tires during the test. The "bar" and "rope" removed 78% and 40% of the mud, respectively. / Master of Science

Daily production data were obtained from 22 independent contractors. The collected information included the contractors' estimates of their maximum production capacity and the actual production achieved. Explanations were requested to explain any difference between actual and achieved production. Most frequent causes of lost production were: 1) adverse weather, 2) quotas,3) moving. Other reasons for delays included mechanical problems, and labor problems. Median capacity utilization for the study period was 70%. The region of operation had a significant influence on capacity utilization: Contractors from the Piedmont had the highest capacity utilization (median of 81%), Coastal Plain (70%), and southern Appalachian (63%). Rain had the most impact on contractors. Above average rainfall occurred over much of the region during the study period. Stricter environmental regulations are suspected to have increased the impact of rain on harvesting operations. Production quotas affected a number of loggers during the study, especially in the southern Appalachians. Capacity losses accounted for six to nineteen percent for these contractors. Overall, weather proved much more significant than quota. A model was developed to estimate the cumulative cost of extra capacity in relation to the risk of wood outage at the consuming mill. The model could serve as a starting point for a better understanding of stump to mill wood flow. Quality control statistical methods were adapted to analyze logging operations systems. Run charts, control charts, and cusum charts were used to measure variability in systems' production. Variation in production levels appear to be increasing with increased regulation. Elasticity has become essential for contractors to maintain profitability. High production during the relatively short periods of good weather and no quotas generated the margin necessary to sustain the contractors during periods of little or no production. Findings suggested that long term production record should be maintained for a selected group of contractors. Better knowledge on the southern wood supply system sustain ability and adaptability could be developed for use in operation and inventory management planning. An increased knowledge and a broader use of quality management tools should be considered in wood procurement. / Master of Science

The problem of optimal land organization was approached via a general methodology to aggregate finely distinguished planning unit areas of an even-aged ponderosa pine forest in Northwestern Mexico. Factor analysis was applied to eighteen timber inventory variables to produce four independent and meaningful constructs that explained 87% of the total variable set’s variation. Next, each planning unit area was characterized by its factor scores and an Euclidean-metric based analysis was applied. The resultant Dendrograrn’s structure helped to define four levels of land aggregation that were evaluated with the same forest management policy. This policy simulated current Mexican forestry guidelines such as replacement stand’s regimes based on maximum mean annual increment, and area volume constraints for timber harvest scheduling. Then, the present value-maximizing timber harvest schedules for each level of land organization was found by using LP Model 1 formulations. Results showed that timber harvesting net benefits varied between 1.3% and 7.0% across levels of land aggregation. This fact was a consequence of the biophysical homogeneity of the forest and the Mexican assumptions of prices and flat costs for overhead and planning. Theoretical considerations indicated that if overhead and planning costs are properly considered for every level of land aggregation, the study’s methodology could show a greater present value difference between alternative levels of land organization. / Ph. D.