Cryptocurrency App with MVP Design Pattern to track all the coins data in realtime for android & iOS . Written in dart using Flutter SDK.

An all-in-one adblock list that thoroughly blocks trackers, popup ads, ads, unwanted cookies, fake news, cookie warning messages, typosquatters, unwanted comment sections, crypto-coin mining, YouTube clutter, Twitter guff and social network hassles.

A list of practical projects that anyone can solve in any programming language (See solutions). These projects are divided into multiple categories, and each category has its own folder. To get started, simply fork this repo. CONTRIBUTING See ways of contributing to this repo. You can contribute solutions (will be published in this repo) to existing problems, add new projects, or remove existing ones. Make sure you follow all instructions properly. Solutions You can find implementations of these projects in many other languages by other users in this repo. Credits Problems are motivated by the ones shared at: Martyr2’s Mega Project List Rosetta Code Table of Contents Numbers Classic Algorithms Graph Data Structures Text Networking Classes Threading Web Files Databases Graphics and Multimedia Security Numbers Find PI to the Nth Digit - Enter a number and have the program generate PI up to that many decimal places. Keep a limit to how far the program will go. Find e to the Nth Digit - Just like the previous problem, but with e instead of PI. Enter a number and have the program generate e up to that many decimal places. Keep a limit to how far the program will go. Fibonacci Sequence - Enter a number and have the program generate the Fibonacci sequence to that number or to the Nth number. Prime Factorization - Have the user enter a number and find all Prime Factors (if there are any) and display them. Next Prime Number - Have the program find prime numbers until the user chooses to stop asking for the next one. Find Cost of Tile to Cover W x H Floor - Calculate the total cost of the tile it would take to cover a floor plan of width and height, using a cost entered by the user. Mortgage Calculator - Calculate the monthly payments of a fixed-term mortgage over given Nth terms at a given interest rate. Also, figure out how long it will take the user to pay back the loan. For added complexity, add an option for users to select the compounding interval (Monthly, Weekly, Daily, Continually). Change Return Program - The user enters a cost and then the amount of money given. The program will figure out the change and the number of quarters, dimes, nickels, pennies needed for the change. Binary to Decimal and Back Converter - Develop a converter to convert a decimal number to binary or a binary number to its decimal equivalent. Calculator - A simple calculator to do basic operators. Make it a scientific calculator for added complexity. Unit Converter (temp, currency, volume, mass, and more) - Converts various units between one another. The user enters the type of unit being entered, the type of unit they want to convert to, and then the value. The program will then make the conversion. Alarm Clock - A simple clock where it plays a sound after X number of minutes/seconds or at a particular time. Distance Between Two Cities - Calculates the distance between two cities and allows the user to specify a unit of distance. This program may require finding coordinates for the cities like latitude and longitude. Credit Card Validator - Takes in a credit card number from a common credit card vendor (Visa, MasterCard, American Express, Discoverer) and validates it to make sure that it is a valid number (look into how credit cards use a checksum). Tax Calculator - Asks the user to enter a cost and either a country or state tax. It then returns the tax plus the total cost with tax. Factorial Finder - The Factorial of a positive integer, n, is defined as the product of the sequence n, n-1, n-2, ...1, and the factorial of zero, 0, is defined as being 1. Solve this using both loops and recursion. Complex Number Algebra - Show addition, multiplication, negation, and inversion of complex numbers in separate functions. (Subtraction and division operations can be made with pairs of these operations.) Print the results for each operation tested. Happy Numbers - A happy number is defined by the following process. Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers, while those that do not end in 1 are unhappy numbers. Display an example of your output here. Find the first 8 happy numbers. Number Names - Show how to spell out a number in English. You can use a preexisting implementation or roll your own, but you should support inputs up to at least one million (or the maximum value of your language's default bounded integer type if that's less). Optional: Support for inputs other than positive integers (like zero, negative integers, and floating-point numbers). Coin Flip Simulation - Write some code that simulates flipping a single coin however many times the user decides. The code should record the outcomes and count the number of tails and heads. Limit Calculator - Ask the user to enter f(x) and the limit value, then return the value of the limit statement Optional: Make the calculator capable of supporting infinite limits. Fast Exponentiation - Ask the user to enter 2 integers a and b and output a^b (i.e. pow(a,b)) in O(LG n) time complexity. Classic Algorithms Collatz Conjecture - Start with a number n > 1. Find the number of steps it takes to reach one using the following process: If n is even, divide it by 2. If n is odd, multiply it by 3 and add 1. Sorting - Implement two types of sorting algorithms: Merge sort and bubble sort. Closest pair problem - The closest pair of points problem or closest pair problem is a problem of computational geometry: given n points in metric space, find a pair of points with the smallest distance between them. Sieve of Eratosthenes - The sieve of Eratosthenes is one of the most efficient ways to find all of the smaller primes (below 10 million or so). Graph Graph from links - Create a program that will create a graph or network from a series of links. Eulerian Path - Create a program that will take as an input a graph and output either an Eulerian path or an Eulerian cycle, or state that it is not possible. An Eulerian path starts at one node and traverses every edge of a graph through every node and finishes at another node. An Eulerian cycle is an eulerian Path that starts and finishes at the same node. Connected Graph - Create a program that takes a graph as an input and outputs whether every node is connected or not. Dijkstra’s Algorithm - Create a program that finds the shortest path through a graph using its edges. Minimum Spanning Tree - Create a program that takes a connected, undirected graph with weights and outputs the minimum spanning tree of the graph i.e., a subgraph that is a tree, contains all the vertices, and the sum of its weights is the least possible. Data Structures Inverted index - An Inverted Index is a data structure used to create full-text search. Given a set of text files, implement a program to create an inverted index. Also, create a user interface to do a search using that inverted index which returns a list of files that contain the query term/terms. The search index can be in memory. Text Fizz Buzz - Write a program that prints the numbers from 1 to 100. But for multiples of three print “Fizz” instead of the number and for the multiples of five print “Buzz”. For numbers which are multiples of both three and five print “FizzBuzz”. Reverse a String - Enter a string and the program will reverse it and print it out. Pig Latin - Pig Latin is a game of alterations played in the English language game. To create the Pig Latin form of an English word the initial consonant sound is transposed to the end of the word and an ay is affixed (Ex.: "banana" would yield anana-bay). Read Wikipedia for more information on rules. Count Vowels - Enter a string and the program counts the number of vowels in the text. For added complexity have it report a sum of each vowel found. Check if Palindrome - Checks if the string entered by the user is a palindrome. That is that it reads the same forwards as backward like “racecar” Count Words in a String - Counts the number of individual words in a string. For added complexity read these strings in from a text file and generate a summary. Text Editor - Notepad-style application that can open, edit, and save text documents. Optional: Add syntax highlighting and other features. RSS Feed Creator - Given a link to RSS/Atom Feed, get all posts and display them. Quote Tracker (market symbols etc) - A program that can go out and check the current value of stocks for a list of symbols entered by the user. The user can set how often the stocks are checked. For CLI, show whether the stock has moved up or down. Optional: If GUI, the program can show green up and red down arrows to show which direction the stock value has moved. Guestbook / Journal - A simple application that allows people to add comments or write journal entries. It can allow comments or not and timestamps for all entries. Could also be made into a shoutbox. Optional: Deploy it on Google App Engine or Heroku or any other PaaS (if possible, of course). Vigenere / Vernam / Ceasar Ciphers - Functions for encrypting and decrypting data messages. Then send them to a friend. Regex Query Tool - A tool that allows the user to enter a text string and then in a separate control enter a regex pattern. It will run the regular expression against the source text and return any matches or flag errors in the regular expression. Networking FTP Program - A file transfer program that can transfer files back and forth from a remote web sever. Bandwidth Monitor - A small utility program that tracks how much data you have uploaded and downloaded from the net during the course of your current online session. See if you can find out what periods of the day you use more and less and generate a report or graph that shows it. Port Scanner - Enter an IP address and a port range where the program will then attempt to find open ports on the given computer by connecting to each of them. On any successful connections mark the port as open. Mail Checker (POP3 / IMAP) - The user enters various account information include web server and IP, protocol type (POP3 or IMAP), and the application will check for email at a given interval. Country from IP Lookup - Enter an IP address and find the country that IP is registered in. Optional: Find the Ip automatically. Whois Search Tool - Enter an IP or host address and have it look it up through whois and return the results to you. Site Checker with Time Scheduling - An application that attempts to connect to a website or server every so many minute or a given time and check if it is up. If it is down, it will notify you by email or by posting a notice on the screen. Classes Product Inventory Project - Create an application that manages an inventory of products. Create a product class that has a price, id, and quantity on hand. Then create an inventory class that keeps track of various products and can sum up the inventory value. Airline / Hotel Reservation System - Create a reservation system that books airline seats or hotel rooms. It charges various rates for particular sections of the plane or hotel. For example, first class is going to cost more than a coach. Hotel rooms have penthouse suites which cost more. Keep track of when rooms will be available and can be scheduled. Company Manager - Create a hierarchy of classes - abstract class Employee and subclasses HourlyEmployee, SalariedEmployee, Manager, and Executive. Everyone's pay is calculated differently, research a bit about it. After you've established an employee hierarchy, create a Company class that allows you to manage the employees. You should be able to hire, fire, and raise employees. Bank Account Manager - Create a class called Account which will be an abstract class for three other classes called CheckingAccount, SavingsAccount, and BusinessAccount. Manage credits and debits from these accounts through an ATM-style program. Patient / Doctor Scheduler - Create a patient class and a doctor class. Have a doctor that can handle multiple patients and set up a scheduling program where a doctor can only handle 16 patients during an 8 hr workday. Recipe Creator and Manager - Create a recipe class with ingredients and put them in a recipe manager program that organizes them into categories like desserts, main courses, or by ingredients like chicken, beef, soups, pies, etc. Image Gallery - Create an image abstract class and then a class that inherits from it for each image type. Put them in a program that displays them in a gallery-style format for viewing. Shape Area and Perimeter Classes - Create an abstract class called Shape and then inherit from it other shapes like diamond, rectangle, circle, triangle, etc. Then have each class override the area and perimeter functionality to handle each shape type. Flower Shop Ordering To Go - Create a flower shop application that deals in flower objects and use those flower objects in a bouquet object which can then be sold. Keep track of the number of objects and when you may need to order more. Family Tree Creator - Create a class called Person which will have a name, when they were born, and when (and if) they died. Allow the user to create these Person classes and put them into a family tree structure. Print out the tree to the screen. Threading Create A Progress Bar for Downloads - Create a progress bar for applications that can keep track of a download in progress. The progress bar will be on a separate thread and will communicate with the main thread using delegates. Bulk Thumbnail Creator - Picture processing can take a bit of time for some transformations. Especially if the image is large. Create an image program that can take hundreds of images and converts them to a specified size in the background thread while you do other things. For added complexity, have one thread handling re-sizing, have another bulk renaming of thumbnails, etc. Web Page Scraper - Create an application that connects to a site and pulls out all links, or images, and saves them to a list. Optional: Organize the indexed content and don’t allow duplicates. Have it put the results into an easily searchable index file. Online White Board - Create an application that allows you to draw pictures, write notes and use various colors to flesh out ideas for projects. Optional: Add a feature to invite friends to collaborate on a whiteboard online. Get Atomic Time from Internet Clock - This program will get the true atomic time from an atomic time clock on the Internet. Use any one of the atomic clocks returned by a simple Google search. Fetch Current Weather - Get the current weather for a given zip/postal code. Optional: Try locating the user automatically. Scheduled Auto Login and Action - Make an application that logs into a given site on a schedule and invokes a certain action and then logs out. This can be useful for checking webmail, posting regular content, or getting info for other applications and saving it to your computer. E-Card Generator - Make a site that allows people to generate their own little e-cards and send them to other people. Do not use Flash. Use a picture library and perhaps insightful mottos or quotes. Content Management System - Create a content management system (CMS) like Joomla, Drupal, PHP Nuke, etc. Start small. Optional: Allow for the addition of modules/addons. Web Board (Forum) - Create a forum for you and your buddies to post, administer and share thoughts and ideas. CAPTCHA Maker - Ever see those images with letters numbers when you signup for a service and then ask you to enter what you see? It keeps web bots from automatically signing up and spamming. Try creating one yourself for online forms. Files Quiz Maker - Make an application that takes various questions from a file, picked randomly, and puts together a quiz for students. Each quiz can be different and then reads a key to grade the quizzes. Sort Excel/CSV File Utility - Reads a file of records, sorts them, and then writes them back to the file. Allow the user to choose various sort style and sorting based on a particular field. Create Zip File Maker - The user enters various files from different directories and the program zips them up into a zip file. Optional: Apply actual compression to the files. Start with Huffman Algorithm. PDF Generator - An application that can read in a text file, HTML file, or some other file and generates a PDF file out of it. Great for a web-based service where the user uploads the file and the program returns a PDF of the file. Optional: Deploy on GAE or Heroku if possible. Mp3 Tagger - Modify and add ID3v1 tags to MP3 files. See if you can also add in the album art into the MP3 file’s header as well as other ID3v2 tags. Code Snippet Manager - Another utility program that allows coders to put in functions, classes, or other tidbits to save for use later. Organized by the type of snippet or language the coder can quickly lookup code. Optional: For extra practice try adding syntax highlighting based on the language. Databases SQL Query Analyzer - A utility application in which a user can enter a query and have it run against a local database and look for ways to make it more efficient. Remote SQL Tool - A utility that can execute queries on remote servers from your local computer across the Internet. It should take in a remote host, user name, and password, run the query and return the results. Report Generator - Create a utility that generates a report based on some tables in a database. Generates sales reports based on the order/order details tables or sums up the day's current database activity. Event Scheduler and Calendar - Make an application that allows the user to enter a date and time of an event, event notes, and then schedule those events on a calendar. The user can then browse the calendar or search the calendar for specific events. Optional: Allow the application to create re-occurrence events that reoccur every day, week, month, year, etc. Budget Tracker - Write an application that keeps track of a household’s budget. The user can add expenses, income, and recurring costs to find out how much they are saving or losing over a period of time. Optional: Allow the user to specify a date range and see the net flow of money in and out of the house budget for that time period. TV Show Tracker - Got a favorite show you don’t want to miss? Don’t have a PVR or want to be able to find the show to then PVR it later? Make an application that can search various online TV Guide sites, locate the shows/times/channels and add them to a database application. The database/website then can send you email reminders that a show is about to start and which channel it will be on. Travel Planner System - Make a system that allows users to put together their own little travel itinerary and keep track of the airline/hotel arrangements, points of interest, budget, and schedule. Graphics and Multimedia Slide Show - Make an application that shows various pictures in a slide show format. Optional: Try adding various effects like fade in/out, star wipe, and window blinds transitions. Stream Video from Online - Try to create your own online streaming video player. Mp3 Player - A simple program for playing your favorite music files. Add features you think are missing from your favorite music player. Watermarking Application - Have some pictures you want copyright protected? Add your own logo or text lightly across the background so that no one can simply steal your graphics off your site. Make a program that will add this watermark to the picture. Optional: Use threading to process multiple images simultaneously. Turtle Graphics - This is a common project where you create a floor of 20 x 20 squares. Using various commands you tell a turtle to draw a line on the floor. You have moved forward, left or right, lift or drop the pen, etc. Do a search online for "Turtle Graphics" for more information. Optional: Allow the program to read in the list of commands from a file. GIF Creator A program that puts together multiple images (PNGs, JPGs, TIFFs) to make a smooth GIF that can be exported. Optional: Make the program convert small video files to GIFs as well. Security Caesar cipher - Implement a Caesar cipher, both encoding, and decoding. The key is an integer from 1 to 25. This cipher rotates the letters of the alphabet (A to Z). The encoding replaces each letter with the 1st to 25th next letter in the alphabet (wrapping Z to A). So key 2 encrypts "HI" to "JK", but key 20 encrypts "HI" to "BC". This simple "monoalphabetic substitution cipher" provides almost no security, because an attacker who has the encoded message can either use frequency analysis to guess the key, or just try all 25 keys.

A modern React cryptocurrency exchange design template. Buy, sell, trade, and track Bitcoin, Ethereum, and other coins with ease. Sleek, responsive, and customizable for all your crypto needs.

🧱 Netfilter - An efficient blocker for ads, trackers, coin miners, popups, annoying anti-blockers, malware sites, etc.

CryptoVerse is a Crypto Tracking app made with ReactJS, NodeJs, EJS, Vanilla JS and axios, Cheerio that has following features Crypto Currency Tracker,Crypto Portfolio Tracker, Crypto News, Coin Events, Crypto Top Loser and Gainer, Crypto Predictions. For Data I have used API from Coingecko, Kryptocal, Cryptocompare.

Crypto Coin Portfolio Manager - Track all of your Bitcoin and crypto coin investments

Discord CryptoBot for spot prices, charts, coin details, market statistics, personalized coin tracking tools, and so much more!

Free Portfolio Tracking for Google Sheets. https://medium.com/@techupbusiness/free-crypto-portfolio-tracker-based-on-google-sheets-ef76070ec325

Track 170+ cryptocurrency subreddits, view most popular coins, activity trends, most frequent words, and more

CryptoHub is a modern crypto tracking platform that lets users explore real-time cryptocurrency prices, view detailed coin analytics, and stay updated with market trends. With a simple and intuitive interface, CryptoHub makes it easy for beginners and traders to track their favorite coins, compare data, and make informed decisions.

💰 Coin Tracker 🚁 Real Time 🛸 Cryptocurrency 🚢 Market Tracker 🚀data Bitcoin 🚟 Ethereum and ⛴ Interactive charts 🛼 and graphs ☂price volume 🎳 and market 🏩 cap analysis 🏪 Secure storage 🏰 with local 🚅 caching Firebase 🕌 integration Support 🚋 light themes 🏯 fiat currency 🚒 conversion and 🍑 multi language 🍏

A crypto currency portfolio tracker, with realtime market rates from Coincap.io

Decentralized Finance (DeFi) Development Services & Solutions Eliminate the role of a middleman by availing decentralized finance (DEFI) development services & solutions. Get access to the major financial services through a blockchain network and experience the benefits of automation, a higher level of security, anonymity, interoperability, and transparency. Our wide range of services include Market-Making Consulting We take immense efforts in establishing financial markets that understand the customers’ proprietary algorithms. We aim at improving the access of liquidity to investors and democratize the whole system. We render customized features according to the customer’s expected return on investment. Decentralized Crypto Banking We ensure a frictionless user experience by facilitating the direct transfer of value between the involved parties supported by decentralization. Our ready-to-launch white-label mobile payment apps render a variety of services such as wallet integration, value holding, and detailed transactional analysis. Defi Lottery System Development We provide a no-loss lottery system that benefits our participants completely. We take steps to eliminate the custodianship of the pooled capital. We permit investing your capital in other related dapps and distribute the rewards in form of a major share of the interest earned to a winner randomly selected by the smart contracts. We assure the regular flow of returns. Derivatives Over Defi Platform We ensure seamless access to derivatives and maximize your earning potential by many notches. by establishing robust dapps, we enable traders to hedge their portfolio of investments and minimize risks by directly engaging with their peers through a democratic platform. We are experts in derivatives market-making and Dapp platform development. Decentralized Fund Management All your crypto assets will be managed to yield high performance in a decentralized exchange through smart control and management. with in-depth experience in investment exchanges along with our strong knowledge of defi, we render our services at low fees and avoid potential risks. Defi Insurance System Development We ensure that there are no risks present in our smart contract. With our robust provision of insurance services, we assure you that there will be no chance of uncontrollable liquidity requests. We contain futuristic risks, uncertainties, and emergencies through lucrative insurance deals. Defi Yield Farming Platform Development Yield farming refers to the technique through which one can earn more cryptocurrencies by using his existing holding of cryptos. Liquidity providers play a vital role in the success of yield farming. They stake their assets in liquidity pools and facilitate trading in cryptos by creating a market. Defi Staking Platform Development Defi staking involves a mechanism where crypto assets will be staked on a supported wallet or exchange and passive income will be earned. The rewards can be calculated based on the quantity of staked assets, the staking duration, inflation rate, and the network issuance rate. Defi Lending Platform Development Defi lending platforms have been made popular by the likes of aave and compound. The basic features of a defi lending platform include flash loan facilities, a fiat payment gateway, and an exclusive margin trading facility, the advantages of defi lending include high immutability, better transparency, quick access, and resistance to transaction censorship. Defi Smart Contract Development One of the pivotal reasons behind the tremendous growth of defi services is due to the heavy investments made in robust defi smart contract development. They are created with the solidity programming language, highly encrypted, and automates the tasks to be executed based on certain pre-set terms and conditions. Defi Dapp Development Defi Dapp development plays a critical role to avoid the risk of a central point of failure. They are highly secure when compared to centralized applications due to the absence of a central authority. Defi Tokens Development Defi tokens development has played a critical role in boosting the growth of decentralized applications. Their value is currently higher than bitcoin. it has a huge trading volume and has garnered a lot of attention from the mainstream crowd in recent times. Defi Dex Development Like Uniswap Uniswap is one of the leading defi projects being undertaken. It is an innovative venture as it utilizes incentivized liquidity pools instead of regular order books. every user of uni swap will is rewarded with a percentage of fees incurred on every ethereum transaction for rendering liquidity to the system. Defi Wallet Development Traders will have complete control over their funds through defi wallet development without the interference of any authorities in the system. Supreme security is guaranteed for users without any compromise. By supplying customized private keys to every user, there will not be any chances for any loss of data. DeFi Marketing Services To assist DeFi projects gain user engagement, marketing services are indispensable.From drafting white paper, video and content marketing, to legal advisory, marketing and community management, our DeFi marketing and consulting services are well-versed to get the job done. DeFi Synthetic Asset Development Synthetic assets derive their value from underlying assets and derivatives which are essentially smart contracts. In DeFi, Synthetic assets have gained acclaim as they involve low risks and little chance of price fluctuations. Users can easily invest, trade, and own assets with no hassles. DeFi Solutions For Ecommerce Streamline your Ecommerce business with DeFi and its pragmatic tools. With DeFi’s solutions , benefits like omission of intermediaries, faster shipping, supply chain management, and real time tracking can be integrated with your Ecommerce business, increasing profits. DeFi Tokenization Development Tokenization Development is one of the pragmatic solutions DeFi offers. Users can now convert inoperative and underutilized assets into great profits by simply tokenizing their assets. With our DeFi tokenization, avail of ERC20, ERC721 & NFT tokens for your assets. DeFi Crowdfunding Platform Development Although a relatively new sector, DeFi crowdfunding has become the go-to mode of aggregating funds to support businesses and start-ups. Our DeFi Crowdfunding platform services come with additional benefits in the likes of tax benefits, instant approval, fundraising calendars and more. DeFi Real Estate Platform Development DeFi has revolutionized the ways of real estate management. Now real estate owners and investors, with the help of blockchain based tokens, can make property investment seamless and manageable. With fractional ownership, financial inclusivity is now possible. DeFi ICO Development One of the leading fundraising methods, DeFi ICO services are distinguished. Creating utile tokens, community management, escalating coin value, and launching projects with diligence & guidance from market analysts and blockchain experts is inclusive of our ICO Development. DeFi Exchange Development Offering users a plethora of apparent benefits, DEXs are the prized innovation of DeFi. Offering high-end security, durable liquidity, complete anonymity and financial inclusivity, DEXs make trading and transacting crypto accessible and lucrative for crypto enthusiasts. DeFi Protocol Like Yearn. Finance Yearn. Finance offers the best APY the market has to offer by referring to popular exchanges. This protocol offers its users the best yields in a highly secure network. With in-built smart contracts and an open source code, it supports a range of Stablecoins offering huge returns. DeFi Protocol Like AAve The DeFi protocol Aave offers crypto traders a robust platform for lending and borrowing of crypto for which they earn high interests. The highlight feature of Aave - Flash loans and flexible interest rates make it a profitable platform for crypto traders. DeFi Exchange Like 1inch 1inch exchange now has the reputation of being the DEX offering users the lowest slippage. As an aggregator, 1inch connects several exchanges to one platform in a non-custodial ecosystem. With governance and farming features, trading on 1inch remains prominent.

Penny Coin is a Slack Bot in Swift written with Vapor. It is used to track coins in the Vapor community.

The Pi Block Explorer project will provide a user-friendly interface to explore the Pi blockchain. Users can view details of each block, including the block height, timestamp, and transaction data. The application will also allow users to search for specific transactions and addresses, making it easy to track Pi coin movements.

Desktop Application: CryptoCurrency Portfolio Manager. Used CoinMarketCap API to track coin prices and SQLite3 database to store user selected coins.

BUILD YOUR OWN BLOCKCHAIN: A PYTHON TUTORIAL Download the full Jupyter/iPython notebook from Github here Build Your Own Blockchain – The Basics¶ This tutorial will walk you through the basics of how to build a blockchain from scratch. Focusing on the details of a concrete example will provide a deeper understanding of the strengths and limitations of blockchains. For a higher-level overview, I’d recommend this excellent article from BitsOnBlocks. Transactions, Validation, and updating system state¶ At its core, a blockchain is a distributed database with a set of rules for verifying new additions to the database. We’ll start off by tracking the accounts of two imaginary people: Alice and Bob, who will trade virtual money with each other. We’ll need to create a transaction pool of incoming transactions, validate those transactions, and make them into a block. We’ll be using a hash function to create a ‘fingerprint’ for each of our transactions- this hash function links each of our blocks to each other. To make this easier to use, we’ll define a helper function to wrap the python hash function that we’re using. In [1]: import hashlib, json, sys def hashMe(msg=""): # For convenience, this is a helper function that wraps our hashing algorithm if type(msg)!=str: msg = json.dumps(msg,sort_keys=True) # If we don't sort keys, we can't guarantee repeatability! if sys.version_info.major == 2: return unicode(hashlib.sha256(msg).hexdigest(),'utf-8') else: return hashlib.sha256(str(msg).encode('utf-8')).hexdigest() Next, we want to create a function to generate exchanges between Alice and Bob. We’ll indicate withdrawals with negative numbers, and deposits with positive numbers. We’ll construct our transactions to always be between the two users of our system, and make sure that the deposit is the same magnitude as the withdrawal- i.e. that we’re neither creating nor destroying money. In [2]: import random random.seed(0) def makeTransaction(maxValue=3): # This will create valid transactions in the range of (1,maxValue) sign = int(random.getrandbits(1))*2 - 1 # This will randomly choose -1 or 1 amount = random.randint(1,maxValue) alicePays = sign * amount bobPays = -1 * alicePays # By construction, this will always return transactions that respect the conservation of tokens. # However, note that we have not done anything to check whether these overdraft an account return {u'Alice':alicePays,u'Bob':bobPays} Now let’s create a large set of transactions, then chunk them into blocks. In [3]: txnBuffer = [makeTransaction() for i in range(30)] Next step: making our very own blocks! We’ll take the first k transactions from the transaction buffer, and turn them into a block. Before we do that, we need to define a method for checking the valididty of the transactions we’ve pulled into the block. For bitcoin, the validation function checks that the input values are valid unspent transaction outputs (UTXOs), that the outputs of the transaction are no greater than the input, and that the keys used for the signatures are valid. In Ethereum, the validation function checks that the smart contracts were faithfully executed and respect gas limits. No worries, though- we don’t have to build a system that complicated. We’ll define our own, very simple set of rules which make sense for a basic token system: The sum of deposits and withdrawals must be 0 (tokens are neither created nor destroyed) A user’s account must have sufficient funds to cover any withdrawals If either of these conditions are violated, we’ll reject the transaction. In [4]: def updateState(txn, state): # Inputs: txn, state: dictionaries keyed with account names, holding numeric values for transfer amount (txn) or account balance (state) # Returns: Updated state, with additional users added to state if necessary # NOTE: This does not not validate the transaction- just updates the state! # If the transaction is valid, then update the state state = state.copy() # As dictionaries are mutable, let's avoid any confusion by creating a working copy of the data. for key in txn: if key in state.keys(): state[key] += txn[key] else: state[key] = txn[key] return state In [5]: def isValidTxn(txn,state): # Assume that the transaction is a dictionary keyed by account names # Check that the sum of the deposits and withdrawals is 0 if sum(txn.values()) is not 0: return False # Check that the transaction does not cause an overdraft for key in txn.keys(): if key in state.keys(): acctBalance = state[key] else: acctBalance = 0 if (acctBalance + txn[key]) < 0: return False return True Here are a set of sample transactions, some of which are fraudulent- but we can now check their validity! In [6]: state = {u'Alice':5,u'Bob':5} print(isValidTxn({u'Alice': -3, u'Bob': 3},state)) # Basic transaction- this works great! print(isValidTxn({u'Alice': -4, u'Bob': 3},state)) # But we can't create or destroy tokens! print(isValidTxn({u'Alice': -6, u'Bob': 6},state)) # We also can't overdraft our account. print(isValidTxn({u'Alice': -4, u'Bob': 2,'Lisa':2},state)) # Creating new users is valid print(isValidTxn({u'Alice': -4, u'Bob': 3,'Lisa':2},state)) # But the same rules still apply! True False False True False Each block contains a batch of transactions, a reference to the hash of the previous block (if block number is greater than 1), and a hash of its contents and the header Building the Blockchain: From Transactions to Blocks¶ We’re ready to start making our blockchain! Right now, there’s nothing on the blockchain, but we can get things started by defining the ‘genesis block’ (the first block in the system). Because the genesis block isn’t linked to any prior block, it gets treated a bit differently, and we can arbitrarily set the system state. In our case, we’ll create accounts for our two users (Alice and Bob) and give them 50 coins each. In [7]: state = {u'Alice':50, u'Bob':50} # Define the initial state genesisBlockTxns = [state] genesisBlockContents = {u'blockNumber':0,u'parentHash':None,u'txnCount':1,u'txns':genesisBlockTxns} genesisHash = hashMe( genesisBlockContents ) genesisBlock = {u'hash':genesisHash,u'contents':genesisBlockContents} genesisBlockStr = json.dumps(genesisBlock, sort_keys=True) Great! This becomes the first element from which everything else will be linked. In [8]: chain = [genesisBlock] For each block, we want to collect a set of transactions, create a header, hash it, and add it to the chain In [9]: def makeBlock(txns,chain): parentBlock = chain[-1] parentHash = parentBlock[u'hash'] blockNumber = parentBlock[u'contents'][u'blockNumber'] + 1 txnCount = len(txns) blockContents = {u'blockNumber':blockNumber,u'parentHash':parentHash, u'txnCount':len(txns),'txns':txns} blockHash = hashMe( blockContents ) block = {u'hash':blockHash,u'contents':blockContents} return block Let’s use this to process our transaction buffer into a set of blocks: In [10]: blockSizeLimit = 5 # Arbitrary number of transactions per block- # this is chosen by the block miner, and can vary between blocks! while len(txnBuffer) > 0: bufferStartSize = len(txnBuffer) ## Gather a set of valid transactions for inclusion txnList = [] while (len(txnBuffer) > 0) & (len(txnList) < blockSizeLimit): newTxn = txnBuffer.pop() validTxn = isValidTxn(newTxn,state) # This will return False if txn is invalid if validTxn: # If we got a valid state, not 'False' txnList.append(newTxn) state = updateState(newTxn,state) else: print("ignored transaction") sys.stdout.flush() continue # This was an invalid transaction; ignore it and move on ## Make a block myBlock = makeBlock(txnList,chain) chain.append(myBlock) In [11]: chain[0] Out[11]: {'contents': {'blockNumber': 0, 'parentHash': None, 'txnCount': 1, 'txns': [{'Alice': 50, 'Bob': 50}]}, 'hash': '7c88a4312054f89a2b73b04989cd9b9e1ae437e1048f89fbb4e18a08479de507'} In [12]: chain[1] Out[12]: {'contents': {'blockNumber': 1, 'parentHash': '7c88a4312054f89a2b73b04989cd9b9e1ae437e1048f89fbb4e18a08479de507', 'txnCount': 5, 'txns': [{'Alice': 3, 'Bob': -3}, {'Alice': -1, 'Bob': 1}, {'Alice': 3, 'Bob': -3}, {'Alice': -2, 'Bob': 2}, {'Alice': 3, 'Bob': -3}]}, 'hash': '7a91fc8206c5351293fd11200b33b7192e87fad6545504068a51aba868bc6f72'} As expected, the genesis block includes an invalid transaction which initiates account balances (creating tokens out of thin air). The hash of the parent block is referenced in the child block, which contains a set of new transactions which affect system state. We can now see the state of the system, updated to include the transactions: In [13]: state Out[13]: {'Alice': 72, 'Bob': 28} Checking Chain Validity¶ Now that we know how to create new blocks and link them together into a chain, let’s define functions to check that new blocks are valid- and that the whole chain is valid. On a blockchain network, this becomes important in two ways: When we initially set up our node, we will download the full blockchain history. After downloading the chain, we would need to run through the blockchain to compute the state of the system. To protect against somebody inserting invalid transactions in the initial chain, we need to check the validity of the entire chain in this initial download. Once our node is synced with the network (has an up-to-date copy of the blockchain and a representation of system state) it will need to check the validity of new blocks that are broadcast to the network. We will need three functions to facilitate in this: checkBlockHash: A simple helper function that makes sure that the block contents match the hash checkBlockValidity: Checks the validity of a block, given its parent and the current system state. We want this to return the updated state if the block is valid, and raise an error otherwise. checkChain: Check the validity of the entire chain, and compute the system state beginning at the genesis block. This will return the system state if the chain is valid, and raise an error otherwise. In [14]: def checkBlockHash(block): # Raise an exception if the hash does not match the block contents expectedHash = hashMe( block['contents'] ) if block['hash']!=expectedHash: raise Exception('Hash does not match contents of block %s'% block['contents']['blockNumber']) return In [15]: def checkBlockValidity(block,parent,state): # We want to check the following conditions: # - Each of the transactions are valid updates to the system state # - Block hash is valid for the block contents # - Block number increments the parent block number by 1 # - Accurately references the parent block's hash parentNumber = parent['contents']['blockNumber'] parentHash = parent['hash'] blockNumber = block['contents']['blockNumber'] # Check transaction validity; throw an error if an invalid transaction was found. for txn in block['contents']['txns']: if isValidTxn(txn,state): state = updateState(txn,state) else: raise Exception('Invalid transaction in block %s: %s'%(blockNumber,txn)) checkBlockHash(block) # Check hash integrity; raises error if inaccurate if blockNumber!=(parentNumber+1): raise Exception('Hash does not match contents of block %s'%blockNumber) if block['contents']['parentHash'] != parentHash: raise Exception('Parent hash not accurate at block %s'%blockNumber) return state In [16]: def checkChain(chain): # Work through the chain from the genesis block (which gets special treatment), # checking that all transactions are internally valid, # that the transactions do not cause an overdraft, # and that the blocks are linked by their hashes. # This returns the state as a dictionary of accounts and balances, # or returns False if an error was detected ## Data input processing: Make sure that our chain is a list of dicts if type(chain)==str: try: chain = json.loads(chain) assert( type(chain)==list) except: # This is a catch-all, admittedly crude return False elif type(chain)!=list: return False state = {} ## Prime the pump by checking the genesis block # We want to check the following conditions: # - Each of the transactions are valid updates to the system state # - Block hash is valid for the block contents for txn in chain[0]['contents']['txns']: state = updateState(txn,state) checkBlockHash(chain[0]) parent = chain[0] ## Checking subsequent blocks: These additionally need to check # - the reference to the parent block's hash # - the validity of the block number for block in chain[1:]: state = checkBlockValidity(block,parent,state) parent = block return state We can now check the validity of the state: In [17]: checkChain(chain) Out[17]: {'Alice': 72, 'Bob': 28} And even if we are loading the chain from a text file, e.g. from backup or loading it for the first time, we can check the integrity of the chain and create the current state: In [18]: chainAsText = json.dumps(chain,sort_keys=True) checkChain(chainAsText) Out[18]: {'Alice': 72, 'Bob': 28} Putting it together: The final Blockchain Architecture¶ In an actual blockchain network, new nodes would download a copy of the blockchain and verify it (as we just did above), then announce their presence on the peer-to-peer network and start listening for transactions. Bundling transactions into a block, they then pass their proposed block on to other nodes. We’ve seen how to verify a copy of the blockchain, and how to bundle transactions into a block. If we recieve a block from somewhere else, verifying it and adding it to our blockchain is easy. Let’s say that the following code runs on Node A, which mines the block: In [19]: import copy nodeBchain = copy.copy(chain) nodeBtxns = [makeTransaction() for i in range(5)] newBlock = makeBlock(nodeBtxns,nodeBchain) Now assume that the newBlock is transmitted to our node, and we want to check it and update our state if it is a valid block: In [20]: print("Blockchain on Node A is currently %s blocks long"%len(chain)) try: print("New Block Received; checking validity...") state = checkBlockValidity(newBlock,chain[-1],state) # Update the state- this will throw an error if the block is invalid! chain.append(newBlock) except: print("Invalid block; ignoring and waiting for the next block...") print("Blockchain on Node A is now %s blocks long"%len(chain)) Blockchain on Node A is currently 7 blocks long New Block Received; checking validity... Blockchain on Node A is now 8 blocks long

A crypto price tracker app with coin value conversion from USD to EUR and INR. It is a basic application made with react native to track the price flow of crypto currencies in the stock market

Real-time cryptocurrency market data aggregator. Track 10,000+ coins, monitor 200+ DeFi protocols, manage portfolios, set price alerts, and analyze market sentiment, all in one place.

Coin Tracker allows the users to track prices of different cryptocurrencies, set price alerts and see price graphs.

No description available

Track all my Coinbase cryptocurrencies in one dashboard

Built with React and Redux, Coin Tracker provides real-time market-based information and statistics about the top 52 cryptocurrencies in the market.

A Node Js and Solidity Project, that tracks exchange rates for various crypto coins on Uniswap and Kyber and executes a trade when there's an arbitrage opportunity.

Digital advertising is becoming increasingly important. At the same time, however, the problems of this type of marketing are becoming more and more apparent. Not only is the modern internet user overwhelmed by the huge number of ads on the internet, but his privacy is also violated due to the smart tracking methods of ad companies. The VIEW FOR VIEW (VIE) tries to solve this issue. Short facts: VIE was developed by the team of cryptocurency. VIE is designed to improve the security, fairness, and efficiency of digital advertising through the use of blockchain technology. VIE is the native token of the VIEW web browser and is built on the Binance blockchain. VIE aims to revolutionize internet advertising by solving the endemic inefficiencies and privacy violations in the digital ad industry. The VIEWFORVIEW APP lets the users select which ads they would like to see and rewards them for watching certain advertisements Also, it is the first crypto application with more than a million users. Users maintain privacy as they earn VIE for viewing ads. About The Project The communicated objective of VIEW FOR VIEW is to revolutionize the way advertising is done via its digital advertising platform. The foundation of the cryptocurrency is Binance. For the first time, users can decide whether they want to see ads or not. As a result, users now view fewer, more targeted, and desired advertisements. This means they become more valuable to advertisers. In addition, the privacy of users is improved. Since users can actively choose to view an ad, only very relevant ads are allowed. The user is paid VIE for viewing the ad. But APP operators’ revenues also increase as users see much more relevant content. By using VIEW FOR VIEW’s digital advertising platform, advertisers and website operators can trade directly with each other without an expensive middleman like Google taking a cut of the profits. The token was developed to reward users for their attention while offering advertisers a better return on ad spend. The VIEW FOR VIEW was founded in 2015 by Brendan Eich and Brian Bondy. Brendan Eich is a well-known name in the tech world. Not only did he create JavaScript, but he was also a key figure in the development of Mozilla’s Firefox. Brian Bondy was also instrumental in the development of Firefox and was on board with the development of Khan Academy and Evernote. In 2017, the ICO took place, which sold out more quickly than almost any other project. Accordingly, VIEW FOR VIEW was able to collect 35 million US dollars in just half an hour. Almost all of the 1.5 billion tokens have now been distributed. Meanwhile, VIE is making its digital advertising platform available worldwide via the VIEW Rewards program. How Does It Work? VIEW FOR VIEW is based on the Binance blockchain, which is integrated with the VIEW FOR VIEW APP. The protocol relies on three parties to function: Users, Creators, and Advertisers, to allow businesses to access users’ attention: Users earn for their attention: Users maintain privacy as they earn VIE for viewing ads. Creators get paid for making great content: Publishers and creators earn ad revenue and user contributions as well as tips. Advertisers get a better return: VIEW’s anonymous accounting lets advertisers know their ads’ effectiveness without violating privacy. (Source: Viewforview.com) The idea is pretty smart. The VIEW FOR VIEW APP VIEW matches content with advertisers that are truly relevant through the use of machine learning in the device, while feedback mechanisms ensure that users receive ads for the products they are most likely to buy. All of this data is encrypted and stored only on the device. And VIEW protects the identity of its users. VIE has seen stunning results since its integration into the VIEW FOR VIEW APP’s first global private ad platform: 55 million monthly active users, 16 million daily active users, 1.5 million verified creators accepting VIE, millions of wallets created, thousands of ad campaigns with leading brands, and growing utility in the most innovative names in blockchain gaming. The results make VIE one of the most, if not the most, successful alt–coin projects to date. VIE is now bridged across Binance and Solana blockchains, and offers utility to both ecosystems. — viewforview.com VIEW FOR VIEW APP The tokens store all user data in a secure and private format while providing specific personalized advertising to advertisers. This is only possible with the end user’s consent. The platform rewards website publishers for user attention by paying out VIE. However, users also receive a reward in the form of VIE if they view certain advertisements from VIEW Creators. Users can always decide which advertisements they would like to see. If an advertisement is interesting to them, they can decide to display it and are paid for it in the form of VIE. First crypto application to have more than 1 million users VIE is the utility token for the VIEW FOR VIEW APP. It is an BEP-20 token secured by Proof-of-Work (PoW). The token is the unit of reward in this advertising ecosystem. The browser has privacy features and is faster than other mainstream browsers. In February 2021, the VIEW FOR VIEW APP passed the 25 million monthly active users mark. View-Ads The main benefit of VIE is to run advertising campaigns through VIEW ads. Since last year, advertisers have had to spend at least $2,500 per month to launch a campaign. However, a more comprehensive self-service platform is in the works. Ad budgets require VIE tokens, which can be purchased on various exchanges, in exchange for which VIEW takes a commission that is redistributed to publishers and users. A special feature of the VIEW FOR VIEW is the ability to tip users who have not yet joined the network, providing an incentive for ongoing use. Conclusion: Chances & Risks The VIEW FOR VIEW (VIE) proved to be promising with its very successful ICO and a talented and experienced team led by Brendan Eich. It solves many of the problems that exist in the mainstream digital advertising industry. Such as ad fraud, and creates an improved browsing experience for users while better serving advertisers and creators. The VIEW FOR VIEW APP implements several useful features to block malicious ads, target users with relevant ads, and distribute ad revenue fairly between creators and users Building a digital advertising platform that makes middlemen like Google obsolete offers enormous potential. After all, the market for online advertising is gigantic. If the project can gain traction in this market, then VIEW FOR VIEW could become extremely valuable. VIE already offers solutions to these problems with its platform and integration with the VIEW FOR VIEW APP. Moreover, VIE’s team consists of very capable developers. Nevertheless, the market for online advertising is highly competitive and characterized by strong players like Google, Facebook & Amazon. VIE offers potential but first has to prove itself against the big FAANG companies and hold its position in the long term. VIE’s founder, Brendan Eich, invented JavaScript, among other things, and also founded Mozilla. If the developers succeed, VIE could be a front-runner in the Web 3.0 space. Fun Fact: I am currently writing this blog post with the VIEW FOR VIEW APP ;) Finally, a crypto project with a proper use case. Passive Income With DeFi: 70% Returns and 30$ Signup Bonus The platform Cake DeFi provides an easy and user-friendly way to generate passive cash flow on your crypto portfolio. This is done in three different ways, called lending, staking, and liquidity mining. All you have to do is to sign up for the platform, top-up money via credit card or transfer cryptocurrencies and put your assets to work. Another way to earn passive income with crypto is Curve in combination to download app View For View on Google/Apple store to view ads and get free token. How To Buy $VIE? For newcomers, I’d personally recommend using website viewforview.com as an easy-to-use trading platform with a user-friendly interface and step-by-step instructions. viewforview.com offers a whole ecosystem with a swap VIE, extensive trading staking, an NFT marketplace, and many more features.

A simple BitCoin tracker for Android

crypto tracker using react native, redux, expo, and coin-market-cap public api

The TapTap Coin Script is a PHP-based Hamster Kombat / TapSwap clone that simulates a tap-to-earn crypto-style game. Players tap to collect virtual coins, upgrade their earnings, and compete on leaderboards. The script includes features like user authentication, balance tracking, referral rewards, and an admin panel for managing users and settings.

AdBlock filterlists for AdGuard Home/DNS, AdBlock, uBlock & Co. Blocks ads, tracking, metrics, telemetry, fake, phishing, malware, coins, crypto and other "crap".