April Fools Pranks with a Squid Proxy Server

Introduction Note: This guide was tested using Ubuntu Server 14.04.4 LTS. This is a HowTo for setting up Upside-Down-Ternet on Ubuntu. Basically, when a user browses the web, all the images are flipped upside-down. While it's not useful, it's quite a good April Fool's prank. The process uses a transparent proxy, web server, and script to flip the images. Web traffic is routed to the proxy, instead of the default gateway, which is intercepted by the proxy which then downloads and modifies the images and then serves them back to the client browser. Setting up the Proxy The proxy used in this guide is Squid v3.3.8. The IP of this server is 192.168.113.253. Installation Configuration Edit the configuration file located in…

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Signing commits using GPG in Git

Git is cryptographically secure, but it’s not foolproof. If you’re taking work from others on the internet and want to verify that commits are actually from a trusted source, Git has a few ways to sign and verify work using GPG. Introduction to GPG First of all, if you want to sign anything you need to get GPG configured and your personal key installed. If you don’t have a key installed, you can generate one with gpg --gen-key. Once you have a private key to sign with, you can configure Git to use it for signing things by setting the user.signingkey config setting. Now Git will use your key by default to sign tags and commits if you want. Add…

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Random Projection

Introduction In mathematics and statistics, random projection is a technique used to reduce the dimensionality of a set of points which lie in Euclidean space. Random projection methods are powerful methods known for their simplicity and less erroneous output compared with other methods. According to experimental results, random projection preserve distances well, but empirical results are sparse. Consider a problem as follows: We have a set of n points in a high-dimensional Euclidean space \(\mathbf{R}^d\). We want to project the points onto a space of low dimension \(\mathbf{R}^k\) in such a way that pairwise distances of the points are approximately the same as before. Formally, we are looking for a map f:\(\mathbf{R}^d\rightarrow\mathbf{R}^k\) such that for any pair of original points u,v,\(\|f(u)-f(v)\|\)

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Decision Tree

What’s decision tree? A decision tree is a flowchart-like structure in which each internal node represents a "test" on an attribute (e.g. whether a coin flip comes up heads or tails), each branch represents the outcome of the test and each leaf node represents a class label (decision taken after computing all attributes). The paths from root to leaf represents classification rules. Overview A decision tree is a flowchart-like structure in which each internal node represents a "test" on an attribute (e.g. whether a coin flip comes up heads or tails), each branch represents the outcome of the test and each leaf node represents a class label (decision taken after computing all attributes). The paths from root to leaf represents…

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Introduction to Java Virtual Machine (JVM)

NOTE: We look at HotSpot in this article, other JVM might behave differently. What is JVM? The Java Virtual Machine is the cornerstone of the Java platform. It is the component of the technology responsible for its hardware- and operating system-independence, the small size of its compiled code, and its ability to protect users from malicious programs. The Java Virtual Machine is an abstract computing machine. Like a real computing machine, it has an instruction set and manipulates various memory areas at run time. The JVM doesn't understand Java typo, that's why you compile your *.java files to obtain *.class files that contain the bytecodes understandable by the JVM. JVM control execution of every Java program. It enables features such as automated…

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Use Server-Sent Event in Spring 4.2

Today, the Spring Framework was released to 4.2 RC2. In Spring 4.2, better application events and Server-Sent Event(SSE) are supported. In this article, I'll introduce you to the two new features. What's Server-Sent Event Server-sent events (SSE) is a technology where a browser receives automatic updates from a server via an HTTP connection. The Server-Sent Events EventSource API is standardized as part of HTML5 by the W3C. Server-sent event is a standard describing how servers can initiate data transmission toward clients once an initial client connection has been established. They are commonly used to send message updates or continuous data streams to a browser client and are designed to enhance native, cross-browser streaming through a JavaScript API called EventSource, through…

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