Manvendra Singh manu-chroma

Algorithm

A secret byte you want to read is stored at inaccessible memory location priv_mem.
The sender triggers an access exception by attempting to read priv_mem.
Due to CPU optimization (out-of-order execution), the load of secret from priv_mem and the use of its value in (4) and (5) below may execute before the exception is triggered.
Calculate an offset into a known array probe by multiplying secret by the width of a cache line (or whatever block size the CPU typically fetches, like a 4096-byte page). This guarantees each of those 256 possible offsets will cache separately.
Load probe[offset], which causes the CPU to cache exactly one chunk of of our array, populating one cache line.
The exception finally triggers, clearing the modified registers...but cached data is not excised.
Iterate over all 256 offsets into probe to find out which one loads fast. You've determined the value of secret.

2023 update

ℹ️ Please note this research is from 2016 when Opera has first added their browser "VPN", even before the "Chinese deal" was closed. They have since introduced some real VPN apps but this below is not about them.

🕵️ Some folks also like to use this article to show a proof that the Opera browser is a spyware or that Opera sells all your data to 3rd parties or something like that. This article here doesn't say anything like that.

When setting up (that's immediately when user enables it in settings) Opera VPN sends few API requests to https://api.surfeasy.com to obtain credentials and proxy IPs, see below, also see The Oprah Proxy.

The browser then talks to a proxy de0.opera-proxy.net (when VPN location is set to Germany), it's IP address can only be resolved from within Opera when VPN is on, it's 185.108.219.42 (or similar, see below). It's an HTTP/S proxy which requires auth.

Python 2.7. Unicode Errors Simply Explained

I know I'm late with this article for about 5 years or so, but people are still using Python 2.x, so this subject is relevant I think.

Some facts first:

Unicode is an international encoding standard for use with different languages and scripts
In python-2.x, there are two types that deal with text.
1. str is an 8-bit string.

unicode is for strings of unicode code points.

##VGG16 model for Keras

This is the Keras model of the 16-layer network used by the VGG team in the ILSVRC-2014 competition.

It has been obtained by directly converting the Caffe model provived by the authors.

Details about the network architecture can be found in the following arXiv paper:

Very Deep Convolutional Networks for Large-Scale Image Recognition

K. Simonyan, A. Zisserman

Git Cheat Sheet

Commands

Getting Started

git init

or

Virtual Hosts on nginx (CSC309)

When hosting our web applications, we often have one public IP address (i.e., an IP address visible to the outside world) using which we want to host multiple web apps. For example, one may wants to host three different web apps respectively for example1.com, example2.com, and example1.com/images on the same machine using a single IP address.

How can we do that? Well, the good news is Internet browsers

ANNOUNCEMENT

I have moved this over to the Tech Interview Cheat Sheet Repo and has been expanded and even has code challenges you can run and practice against!

\

If you find that vagrant box list somehow does not contain a box you previously had, you can sometimes add the box back if you still have the sources for it in ~/.vagrant.d/boxes.

$ cd ~/.vagrant.d/boxes/precise64/0/virtualbox/
$ tar czf ~/precise64.box .
$ vagrant box add precise64 ~/precise64.box 
Downloading box from URL: file:/Users/ryanuber/precise64.box
Extracting box...te: 417M/s, Estimated time remaining: --:--:--)
Successfully added box 'precise64' with provider 'virtualbox'!

	# Description: Boxstarter Script
	# Author: Jess Frazelle <jess@linux.com>
	# Last Updated: 2017-09-11
	#
	# Install boxstarter:
	# . { iwr -useb http://boxstarter.org/bootstrapper.ps1 } \| iex; get-boxstarter -Force
	#
	# You might need to set: Set-ExecutionPolicy RemoteSigned
	#
	# Run this boxstarter by calling the following from an elevated command-prompt:

	#!/usr/bin/env bash

	if [ -z "$1" ]; then
	echo "Usage: bash apifier-get-results <execution_id>"
	exit 1
	fi

	FORMAT="csv"
	EXECUTION_ID="$1"