QuickSync: A Quickly Synchronizing PoS-Based Blockchain Protocol

To implement a blockchain, we need a blockchain protocol for all the nodes to follow. To design a blockchain protocol, we need a block publisher selection mechanism and a chain selection rule. In Proof-of-Stake (PoS) based blockchain protocols, block publisher selection mechanism selects the node to publish the next block based on the relative stake held by the node. However, PoS protocols, such as Ouroboros v1, may face vulnerability to fully adaptive corruptions. In this paper, we propose a novel PoS-based blockchain protocol, QuickSync, to achieve security against fully adaptive corruptions while improving on performance. We propose a metric called block power, a value defined for each block, derived from the output of the verifiable random function based on the digital signature of the block publisher. With this metric, we compute chain power, the sum of block powers of all the blocks comprising the chain, for all the valid chains. These metrics are a function of the block publisher's stake to enable the PoS aspect of the protocol. The chain selection rule selects the chain with the highest chain power as the one to extend. This chain selection rule hence determines the selected block publisher of the previous block. When we use metrics to define the chain selection rule, it may lead to vulnerabilities against Sybil attacks. QuickSync uses a Sybil attack resistant function implemented using histogram matching. We prove that QuickSync satisfies common prefix, chain growth, and chain quality properties and hence it is secure. We also show that it is resilient to different types of adversarial attack strategies. Our analysis demonstrates that QuickSync performs better than Bitcoin by an order of magnitude on both transactions per second and time to finality, and better than Ouroboros v1 by a factor of three on time to finality

The Landscape of Salesforce for Nonprofits: A Report on the Current Marketplace for Apps

Do you use Salesforce as a Constituent Relationship Management database at your organization, or are you considering it? Since it launched in 1999, more than 20,000 nonprofits have employed the cloud-based system, which is made available to them for free through the philanthropic Salesforce Foundation. What's the catch? Making such a powerful system work for the particular needs of a nonprofit isn't always straightforward. This report can tell you everything you need to know.What's in it? To learn more about the benefits and drawbacks of Salesforce, we interviewed nine prominent consultants specializing in implementing Salesforce for nonprofits along with several members of the Salesforce.com Foundation about what the platform does well, and what you'll want to add to it to suit your needs. We evaluated some of the constituent management packages built on top of Salesforce, including the Salesforce Foundation's Nonprofit Starter Pack, which is aimed at turning the sales automation platform into a tool for nonprofits. We also took a look at the universe of add-ons to the base Salesforce platform -- called "apps" because of Salesforce's online marketplace, the App Exchange -- to find out which might be useful to support a nonprofit's processes.The goal for this report was to break down misconceptions about the tool and to collect disparate information in one place to help you make informed decisions. Whether you're already using Salesforce, are thinking about adopting it, or have yet to even consider it, there's information here for you.What's more, we've included a directory of consultants or firms with experience working with nonprofits to implement Salesforce and the additional App Exchange modules that we cover in this report to make it easier for you to find the help you'll need

RF Localization in Indoor Environment

In this paper indoor localization system based on the RF power measurements of the Received Signal Strength (RSS) in WLAN environment is presented. Today, the most viable solution for localization is the RSS fingerprinting based approach, where in order to establish a relationship between RSS values and location, different machine learning approaches are used. The advantage of this approach based on WLAN technology is that it does not need new infrastructure (it reuses already and widely deployed equipment), and the RSS measurement is part of the normal operating mode of wireless equipment. We derive the Cramer-Rao Lower Bound (CRLB) of localization accuracy for RSS measurements. In analysis of the bound we give insight in localization performance and deployment issues of a localization system, which could help designing an efficient localization system. To compare different machine learning approaches we developed a localization system based on an artificial neural network, k-nearest neighbors, probabilistic method based on the Gaussian kernel and the histogram method. We tested the developed system in real world WLAN indoor environment, where realistic RSS measurements were collected. Experimental comparison of the results has been investigated and average location estimation error of around 2 meters was obtained

Handling Confidential Data on the Untrusted Cloud: An Agent-based Approach

Cloud computing allows shared computer and storage facilities to be used by a multitude of clients. While cloud management is centralized, the information resides in the cloud and information sharing can be implemented via off-the-shelf techniques for multiuser databases. Users, however, are very diffident for not having full control over their sensitive data. Untrusted database-as-a-server techniques are neither readily extendable to the cloud environment nor easily understandable by non-technical users. To solve this problem, we present an approach where agents share reserved data in a secure manner by the use of simple grant-and-revoke permissions on shared data.Comment: 7 pages, 9 figures, Cloud Computing 201

An Probability-Based Energy Model on Cache Coherence Protocol with Mobile Sensor Network

Mobile sensor networks (MSNs) are widely used in various domains to monitor, record, compute, and interact the information within an environment. To prolong the life time of each node in MSNs, energy model and conservation should be considered carefully when designing the data communication mechanism in the network. The limited battery volume and high workload on channels worsen the life times of the busy nodes. In this paper, we propose a new energy evaluating methodology of packet transmissions in MSNs, which is based on redividing network layers and describing the synchronous data flow with matrix form. We first introduce the cache coherence layer to the protocol stack of MSNs. Then, we use a set of energy probability matrices to describe and calculate the energy consumption of each state in the protocol. After that, based on our energy model, we will give out an energy evaluating method of the MSNs design, which is suitable for measuring and comparing the energy consumption from different implements of hardware/software. Our experimental results show that our approach achieves a precision with less than 2% error and provides a credible quantitative criterion for energy optimization of data communication in MSNs

Continious Synchronization of Conflict-Free Replicated Relations

Local-first software is an attempt to use the benefits of cloud service while reducing its drawbacks. Local-first software gives the clients ownership and control of their data and makes the service always available. It is achieved by having the primary copy of the service at the client. The most common way to implement local-first software is by utilizing Conflict-free Replicated Datatypes or CRDTs, which are conflict-free by design. Conflict-free Replicated Relations or CRR are CRDT applied to SQL databases. CRR systems require some form of communication middleware to propagate its state so that each site can converge to a common state. Earlier CRR systems have used SSH File Transfer Protocol to propagate states or SFTP, which means writing to disk many times. This thesis focuses mainly on the communication portion of a CRR system applied to an SQLite database called SynQLite. SynQLite is a service that can augment an SQLite database with CRR-support. It also includes the possibility to clone and synchronize with remote sites. The previous version of SynQLite allowed only to pull states from a remote site. We propose a solution where users can synchronize continuously with more than two sites simultaneously. The solution involves creating a centralized leader that other sites can connect to with TCP connections, and the other sites synchronize with the leader. The thesis includes an evaluation process including many experiments. These experiments are used to evaluate how well SynQLite supports local-first properties. This includes testing how SynQLite affects the offline database and how well SynQLite supports synchronizing sites

(I) A Declarative Framework for ERP Systems(II) Reactors: A Data-Driven Programming Model for Distributed Applications

To those who can be swayed by argument and those who know they do not have all the answers This dissertation is a collection of six adapted research papers pertaining to two areas of research. (I) A Declarative Framework for ERP Systems: • POETS: Process-Oriented Event-driven Transaction Systems. The paper describes an ontological analysis of a small segment of the enterprise domain, namely the general ledger and accounts receivable. The result is an event-based approach to designing ERP systems and an abstract-level sketch of the architecture. • Compositional Specification of Commercial Contracts. The paper de-scribes the design, multiple semantics, and use of a domain-specific lan-guage (DSL) for modeling commercial contracts. • SMAWL: A SMAll Workflow Language Based on CCS. The paper show