Evan Saltzman

Cloud-Trust—a Security Assessment Model for Infrastructure as a Service (IaaS) Clouds

The vulnerability of cloud computing systems (CCSs) to advanced persistent threats (APTs) is a significant concern to government and industry. We present a cloud architecture reference model that incorporates a wide range of security controls and best practices, and a cloud security assessment model—Cloud-Trust—that estimates high level security metrics to quantify the degree of confidentiality and integrity offered by a CCS or cloud service provider (CSP). Cloud-Trust is used to assess the security level of four multi-tenant IaaS cloud architectures equipped with alternative cloud security controls. Results show the probability of CCS penetration (high value data compromise) is high if a minimal set of security controls are implemented. CCS penetration probability drops substantially if a cloud defense in depth security architecture is adopted that protects virtual machine (VM) images at rest, strengthens CSP and cloud tenant system administrator access controls, and which employs other network security controls to minimize cloud network surveillance and discovery of live VMs.

Simulating Multivariate Nonhomogeneous Poisson Processes Using Projections

Established techniques for generating an instance of a multivariate NonHomogeneous Poisson Process (NHPP) such as thinning can become highly inefficient as the dimensionality of the process is increased, particularly if the defining intensity (or rate) function has a pronounced peak. To overcome this inefficiency, we propose an alternative approach where one first generates a projection of the NHPP onto a lower-dimensional space, and then extends the generated points to points in the original space by generating from appropriate conditional distributions. One version of this algorithm replaces a high-dimensional problem with a series of one-dimensional problems. Several examples are presented.

Evolution of Predator and Prey Movement into Sink Habitats

Mathematical models of predator‐prey interactions in a patchy landscape are used to explore the evolution of dispersal into sink habitats. When evolution proceeds at a single trophic level (i.e., either prey or predator disperses), three evolutionary outcomes are observed. If predator‐prey dynamics are stable in source habitats, then there is an evolutionarily stable strategy (ESS) corresponding to sedentary phenotypes residing in source habitats. If predator‐prey dynamics are sufficiently unstable, then either an ESS corresponding to dispersive phenotypes or an evolutionarily stable coalition (ESC) between dispersive and sedentary phenotypes emerges. Dispersive phenotypes playing an ESS persist despite exhibiting, on average, a negative per capita growth rate in all habitats. ESCs occur if dispersal into sink habitats can stabilize the predator‐prey interactions. When evolution proceeds at both trophic levels, any combination of monomorphic or dimorphic phenotypes at one or both trophic levels is observed. Coevolution is largely top‐down driven. At low predator mortality rates in sink habitats, evolution of predator movement into sink habitats forestalls evolution of prey movement into sink habitats. Only at intermediate mortality rates is there selection for predator and prey movement. Our results also illustrate an evolutionary paradox of enrichment, in which enriching source habitats can reduce phenotypic diversity.

More Choice In Health Insurance Marketplaces May Reduce The Value Of The Subsidies Available To Low-Income Enrollees

Federal subsidies available to enrollees in health insurance Marketplaces are pegged to the premium of the second-lowest-cost silver plan available in each rating area (as defined by each state). People who qualify for the subsidy contribute a percentage of their income to purchase coverage, and the federal government covers the remaining cost up to the price of that premium. Because the number of plans offered and plan premiums vary substantially across rating areas, the effective value of the subsidy may vary geographically. We found that the availability of more plans in a rating area was associated with lower premiums but higher deductibles for enrollees in the second-lowest-cost silver plan. In rating areas with more than twenty plans, the average deductible in the second-lowest-cost silver plan was nearly

Improving The Affordable Care Act: An Assessment Of Policy Options For Providing Subsidies

1,000 higher than it was in rating areas with fewer than thirteen plans. Because premium costs for second-lowest-cost silver plans are capped, deductibles may be a more salient measure of plan value for enrollees than premiums are. Greater standardization of plans or an alternative approach to calculating the subsidy could provide a more consistent benefit to enrollees across various rating areas.

Air Attack Against Wildfires: Understanding U.S. Forest Service Requirements for Large Aircraft

A key challenge of health reform efforts is to make health insurance affordable for individuals and families who lack coverage without harming those with coverage or increasing federal spending. The Affordable Care Act (ACA) addresses this challenge in part by providing tax subsidies to qualified individuals for purchasing individual insurance and retaining tax exemptions for employer and employee contributions to the cost of premiums of employer-sponsored insurance. These tax exemptions cost approximately

Optimal number of gateways for mobile ad-hoc networks (MANET) with two subnets

250 billion annually in lost tax revenue and have been criticized for favoring higher earners and conferring preferential treatment of employer-sponsored over individual insurance. We analyzed three options for leveling the financial playing field between the two insurance markets by reallocating the value of tax benefits of employer coverage. We found that one option that uses the subsidy formula employed in the insurance Marketplaces under the ACA for both the individual and employer-sponsored insurance markets, and additionally requires the subsidy to be at least

Assessing Policy Options for Subsidies to Improve the Affordable Care Act: One Approach Could Insure More People, Reduce Premiums, and Save

1,250 without an upper income limit on subsidy eligibility imposed, could expand insurance coverage and reduce individual market premiums relative to the ACA with no additional federal spending.

14 Billion per Year

A RAND study sought to help the U.S. Forest Service determine the composition of a fleet of airtankers, scoopers, and helicopters that would minimize the total social costs of wildfires, including the cost of large fires and aircraft costs. The research team developed two models to estimate the social costminimizing portfolios of firefighting aircraft. Both models favored a fleet dominated by scoopers for the prevention of large fires

Effects of the Affordable Care Act on Consumer Health Care Spending and Risk of Catastrophic Health Costs

Early designs of mobile ad-hoc networks (MANETs) assumed they could be scaled to very large topologically flat networks where every node in the network has equal capability and access to the wireless channel. This assumption was called into question in 2000 by Gupta and Kumar [1] who established an asymptotic theoretical limit for node capacity as the number of nodes in a single channel MANET becomes large. Recent field experiments have confirmed that this theoretical limit may be difficult to overcome. To address MANET scalability alternative MANET designs have been developed in which a wireless channel are shared by only a subset of the entire collection of network nodes. Subnets are then linked by gateway nodes that operate on two or more channels and provide connectivity across the entire network. In these MANET designs gateway nodes transmit and receive on multiple subnets and can become bottlenecks in the network if there are too few gateways. On the other hand, if the network contains many gateways, then too much subnet bandwidth may be allocated to gateways and insufficient bandwidth allocated to single channel nodes. This paper examines the design of MANETs based on two subnets and determines the optimal number of gateway nodes which maximizes overall network performance for a uniform message traffic loading.