Shortest Path Problems: Multiple Paths in a Stochastic Graph

Shortest path problems arise in a variety of applications ranging from transportation planning to network routing among others. One group of these problems involves finding shortest paths in graphs where the edge weights are defined by probability distributions. While some research has addressed the problem of finding a single shortest path, no research has been done on finding multiple paths in such graphs. This thesis addresses the problem of finding paths for multiple robots through a graph in which the edge weights represent the probability that each edge will fail. The objective is to find paths for n robots that maximize the probability that at least k of them will arrive at the destination. If we make certain restrictions on the edge weights and topology of the graph, this problem can be solved in O(n log n)time. If we restrict only the topology, we can find approximate solutions which are still guaranteed to be better than the single most reliable path

Meeting the Challenge: Preparing for a Graduate Assistant

The University of Southern Mississippi Libraries Technical Services Department added a Graduate Assistant to the department in Fall 2021. In this session, we will discuss the processes the department undertook to prepare for a successful assistantship opportunity. Through thorough planning the department established a hiring process, training components, and work rotations throughout the department to provide both an extensive emersion into Technical Services work and meet departmental needs for assistance with project completion

Oyster (Crassostrea Virginica [Gmelin, 1791]) Mortality At Prolonged Exposures To High Temperature And Low Salinity

Mortality of two size classes (35 mm) of eastern oysters Crassostrea virginica when exposed to combinations of low salinity (1, 2, 3, and 4) for extended periods (up to 30 days) at summer water temperatures typical of the Virginia Chesapeake Bay subestuaries was examined. A critical salinity-temperature combination of less than two at greater than 28 degrees C for more than 1 wk exposure for oyster mortality is suggested. A review of limited historical salinity-temperature tolerance data suggest selection of local populations of oysters having differing salinity tolerances. Such selection may prove critical to persistence of low-salinity populations in the Chesapeake Bay subestuaries with projected climate change

Developing a Master Food Volunteer Continuing Education Program: A Model for Volunteer Capacity Building

We developed a master food volunteer (MFV) continuing education program (CEP) for MFVs assisting Extension agents with a diabetes self-management program. Our development process included two phases of pilot testing. First, seasoned MFVs tested and provided formative feedback on the first iteration of the MFV CEP modules. After revising the modules in response to their feedback, we evaluated program effectiveness by comparing pretraining/posttraining score change between MFVs who had completed the training (intervention group) and those who had not (comparison group). All test scores increased for intervention group members, whereas half declined for comparison group members. Our process of developing enhanced education to address program-specific volunteer capacity building has broad applicability

FAME: Fast Attribute-based Message Encryption

Time and again, attribute-based encryption has been shown to be the natural cryptographic tool for building various types of conditional access systems with far-reaching applications, but the deployment of such systems has been very slow. A central issue is the lack of an encryption scheme that can operate on sensitive data very efficiently and, at the same time, provides features that are important in practice. This paper proposes the first fully secure ciphertext-policy and key-policy ABE schemes based on a standard assumption on Type-III pairing groups, which do not put any restriction on policy type or attributes. We implement our schemes along with several other prominent ones using the Charm library, and demonstrate that they perform better on almost all parameters of interest

A Domain Transformation for Structure-Preserving Signatures on Group Elements

We present a generic transformation that allows us to use a large class of pairing-based signatures to construct schemes for signing group elements in a structure preserving way. As a result of our transformation we obtain a new efficient signature scheme for signing a vector of group elements that is based only on the well established decisional linear assumption (DLIN). Moreover, the public keys and signatures of our scheme consist of group elements only, and a signature is verified by evaluating a set of pairing-product equations. In combination with the Groth-Sahai proof system, such a signature scheme is an ideal building block for many privacy-enhancing protocols. To do this, we start by proposing a new stateful signature scheme for signing vectors of exponents that is F-unforgeable under weak chosen message attacks. This signature scheme is of independent interest as it is compatible with Groth-Sahai proofs and secure under a computational assumption implied by DLIN. Then we give a general transformation for signing group elements based on signatures (for signing exponents) with efficient non-interactive zero-knowledge proofs. This transform also removes any dependence on state in the signature used to sign exponents. Finally, we obtain our result by instantiating this transformation with the above signature scheme and Groth-Sahai proofs

Substring-Searchable Symmetric Encryption

In this paper, we consider a setting where a client wants to outsource storage of a large amount of private data and then perform substring search queries on the data -- given a data string s and a search string p, find all occurrences of p as a substring of s. First, we formalize an encryption paradigm that we call queryable encryption, which generalizes searchable symmetric encryption (SSE) and structured encryption. Then, we construct a queryable encryption scheme for substring queries. Our construction uses suffix trees and achieves asymptotic efficiency comparable to that of unencrypted suffix trees. Encryption of a string of length n takes O(kn) time and produces a ciphertext of size O(kn), and querying for a substring of length m that occurs z times takes O(km+z) time and three rounds of communication, where k is the security parameter. Our security definition guarantees correctness of query results and privacy of data and queries against a malicious, adaptive adversary. Following the line of work started by Curtmola et al. (ACM CCS 2006), in order to construct more efficient schemes we allow the query protocol to leak some limited information that is captured precisely in the definition. We prove security of our substring-searchable encryption scheme against malicious adversaries, where the query protocol leaks limited information about memory access patterns through the suffix tree of the encrypted string

Private Set Intersection in the Internet Setting From Lightweight Oblivious PRF

We present a new protocol for two-party private set intersection (PSI) with semi-honest security in the plain model and one-sided malicious security in the random oracle model. Our protocol achieves a better balance between computation and communication than existing PSI protocols. Specifically, our protocol is the fastest in networks with moderate bandwidth (e.g., 30 - 100 Mbps). Considering the monetary cost (proposed by Pinkas et al. in CRYPTO 2019) to run the protocol on a cloud computing service, our protocol also compares favorably. Underlying our PSI protocol is a new lightweight multi-point oblivious pesudorandom function (OPRF) protocol based on oblivious transfer (OT) extension. We believe this new protocol may be of independent interest

Structured Encryption and Controlled Disclosure

We consider the problem of encrypting structured data (e.g., a web graph or a social network) in such a way that it can be efficiently and privately queried. For this purpose, we introduce the notion of structured encryption which generalizes previous work on symmetric searchable encryption (SSE) to the setting of arbitrarily-structured data. In the context of cloud storage, structured encryption allows a client to encrypt data without losing the ability to query and retrieve it efficiently. Another application, which we introduce in this work, is to the problem of controlled disclosure, where a data owner wishes to grant access to only part of a massive dataset. We propose a model for structured encryption, a formal security definition and several efficient constructions. We present schemes for performing queries on two simple types of structured data, specifically lookup queries on matrix-structured data, and search queries on labeled data. We then show how these can be used to construct efficient schemes for encrypting graph data while allowing for efficient neighbor and adjacency queries. Finally, we consider data that exhibits a more complex structure such as labeled graph data (e.g., web graphs). We show how to encrypt this type of data in order to perform focused subgraph queries, which are used in several web search algorithms. Our construction is based on our labeled data and basic graph encryption schemes and provides insight into how several simpler algorithms can be combined to generate an efficient scheme for more complex queries

Deja Q: Using Dual Systems to Revisit q-Type Assumptions

After more than a decade of usage, bilinear groups have established their place in the cryptographic canon by enabling the construction of many advanced cryptographic primitives. Unfortunately, this explosion in functionality has been accompanied by an analogous growth in the complexity of the assumptions used to prove security. Many of these assumptions have been gathered under the umbrella of the uber-assumption, yet certain classes of these assumptions -- namely, q-type assumptions -- are stronger and require larger parameter sizes than their static counterparts. In this paper, we show that in certain groups, many classes of q-type assumptions are in fact implied by subgroup hiding (a well-established, static assumption). Our main tool in this endeavor is the dual-system technique, as introduced by Waters in 2009. As a case study, we first show that in composite-order groups, we can prove the security of the Dodis-Yampolskiy PRF based solely on subgroup hiding and allow for a domain of arbitrary size (the original proof only allowed a polynomially-sized domain). We then turn our attention to classes of q-type assumptions and show that they are implied -- when instantiated in appropriate groups -- solely by subgroup hiding. These classes are quite general and include assumptions such as q-SDH. Concretely, our result implies that every construction relying on such assumptions for security (e.g., Boneh-Boyen signatures) can, when instantiated in appropriate composite-order bilinear groups, be proved secure under subgroup hiding instead