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Blockchain Code Example

Github - Lhartikk/naivechain: A Blockchain Implementation In 200 Lines Of Code

Github - Lhartikk/naivechain: A Blockchain Implementation In 200 Lines Of Code

A blockchain implementation in 200 lines of code If nothing happens, download GitHub Desktop and try again. If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again. Naivechain - a blockchain implementation in 200 lines of code All the current implementations of blockchains are tightly coupled with the larger context and problems they (e.g. Bitcoin or Ethereum) are trying to solve. This makes understanding blockchains a necessarily harder task, than it must be. Especially source-code-wisely. This project is an attempt to provide as concise and simple implementation of a blockchain as possible. From Wikipedia : Blockchain is a distributed database that maintains a continuously-growing list of records called blocks secured from tampering and revision. Check also this blog post for a more detailed overview of the key concepts Use Websockets to communicate with other nodes (P2P) Super simple "protocols" in P2P communication No proof-of-work or proof-of-stake: a block can be added to the blockchain without competition For a more extensive tutorial about blockchains, you can check the project Naivecoin . It is based on Naivechain and implements for instance Proof-of-work, transactions and wallets. (set up two connected nodes and mine 1 block) npm installHTTP_PORT=3001 P2P_PORT=6001 npm startHTTP_PORT=3002 P2P_PORT=6002 PEERS=ws://localhost:6001 npm startcurl -H "Content-type:application/json" --data '{"data" : "Some data to the first block"}' (set up three connected nodes and mine a block) docker-compose upcurl -H "Content-type:application/json" --data '{"data" : "Some data to the first block"}' Continue reading >>

The Truth About Blockchain

The Truth About Blockchain

Contracts, transactions, and records of them provide critical structure in our economic system, but they havent kept up with the worlds digital transformation. Theyre like rush-hour gridlock trapping a Formula 1 race car. Blockchain promises to solve this problem. The technology behind bitcoin, blockchain is an open, distributed ledger that records transactions safely, permanently, and very efficiently. For instance, while the transfer of a share of stock can now take up to a week, with blockchain it could happen in seconds. Blockchain could slash the cost of transactions and eliminate intermediaries like lawyers and bankers, and that could transform the economy. But, like the adoption of more internet technologies, blockchains adoption will require broad coordination and will take years. In this article the authors describe the path that blockchain is likely to follow and explain how firms should think about investments in it. Weve all heard that blockchain will revolutionize business, but its going to take a lot longer than many people claim. Like TCP/IP (on which the internet was built), blockchain is a foundational technology that will require broad coordination. The level of complexitytechnological, regulatory, and socialwill be unprecedented. The adoption of TCP/IP suggests blockchain will follow a fairly predictable path. While the journey will take years, its not too early for businesses to start planning. Contracts, transactions, and the records of them are among the defining structures in our economic, legal, and political systems. They protect assets and set organizational boundaries. They establish and verify identities and chronicle events. They govern interactions among nations, organizations, communities, and individuals. They guide managerial and social Continue reading >>

Blockchain Coding: The Many Different Languages You Need!

Blockchain Coding: The Many Different Languages You Need!

Blockchain Coding: The Many different Languages You Need! Blockchain Coding: The Many different Languages You Need! The blockchain technology is incredibly fascinating. It wont be far-fetched to think of a future which will be built entirely on it. So, what do you need to learn in order to start developing on the blockchain? Which languages will give you the edge? In this guide, we will go through some of the more major ones. Problems with developing blockchain software Before we begin, lets checkout some of the challenges that a blockchain developer faces. Creating and maintaining a public blockchain is not easy because of a number of reasons. (Before we continue, a huge shoutout to David Schwartz for his keynote address regarding C++ use in blockchain software development in CPPCON 2016.) Blockchain Coding: The Many different Languages You Need! Blockchains, as David Schwartz puts it, should be fortresses. Firstly, the code is public and open for all to see. Anyone can look over the code and check for bugs and vulnerabilities. However, unlike other open code resources, the downside of finding vulnerabilities on blockchain code is massive. Any programmer can hack in and get away with potentially millions and millions of dollars. Because of these legitimate security concerns, development on blockchain is usually very slow . It is important to keep pace with the network. You cannot fall too far behind and not keep up with all the network demands. You should be well equipped to handle remote and local queries. The blockchain must always perform at its highest possible capabilities, but for that to happen the language chosen must be extremely versatile. The thing is that there are certain tasks in the blockchain which are parallelizable whilst there are some tasks which c Continue reading >>

Blockchain Tutorial A Beginners Guide To Blockchain Technology

Blockchain Tutorial A Beginners Guide To Blockchain Technology

You may go through this recording of Blockchain Tutorial where our instructor has explained the topics in a detailed manner with examples that will help you to understand this concept better. Blockchain Tutorial | Blockchain Technology | Edureka Blockchain technology and the crypto-currencies have today become a parallel platform where people have started performing their standard transactions. Now, if a new system is slowly replacing an existing system then there must be some issues with the current system. We will begin this Blockchain tutorial blog by understanding the problems of the current banking system. Any existing system will have some issues. Let us look at some of the most commonly faced issues with the Banking system: Lets look at an example to understand this issue better: Here, Chandler is sending $100 to Joe butit must pass through a trusted third party like aBank or Financial service company before Joe can receive it. Atransaction fees of 2% is deducted from this amount and Joe only receives $98 at the end of the transaction. Now this may not seem a big amount but imagine if you were sending $100,000 instead of $100, then the transaction fees also increases to $2,000 which is a big amount. As per a reportfrom SNL Financial and CNNMoney, JPMorgan Chase, Bank of America and Wells Fargo earned more than $6 billion fromATM and overdraft feesin 2015 . Double-spendingis an error in digital cashscheme in which the same single digital token is spent twice or more. To help you understand this problem better, let me give you an example: Here Peter has only $500 in his account. He initiates 2 transactions simultaneously to Adam for $400 and Mary for $500. Normally this transaction would not go through as he doesnt have sufficient balance of $900 in his account.Ho Continue reading >>

Php Blockchain | Knowledgearc

Php Blockchain | Knowledgearc

by Hayden Young | Jan 2, 2018 | Blog | 4 comments There is currently a lot of excitement around cryptocurrencies, with many making it rich and many more hoping to get rich quick. While speculating on cryptocurrencies is fun and (currently) profitable, cryptocurrencies are only part of the story of what makes this next technological innovation so ground-breaking. At the heart of cryptocurrencies lies the concept of a blockchain, which, as the name implies, chains a number of blocks together, one after the other, with each block holding information whether transactions, smart contracts, data structures or anything else which needs to record something in an immutable way. While revolutionary, the concept of the blockchain is quite simple; it is really just a linked list data structure. And its very easy to develop your own blockchain in pretty much any programming language you can think of. There are already a number of tutorials on how to build blockchains in various languages and most cryptocurrency code is open sourced and available on Github, so simply browsing source is also a great way to learn how blockchains work. C, C++, Python and Java are the more popular languages for building blockchain technologies but there are also tutorials for Javascript, DotNet and others. Surprisingly, I was unable to turn up a PHP blockchain implementation so I thought I would develop a simple one myself with the aim of better understanding how the blockchain works. Using a blockchain tutorial for Javascript , I coded up a PHP-based blockchain and have made it publicly available on Github in the hope that others may also find it of interest. Currently the implementation is very basic but it highlights the principles of a block chain; blocks can hold arbitrary data, are linked together Continue reading >>

What Is The Simplest Implementation Of The Blockchain? - Updated 2017

What Is The Simplest Implementation Of The Blockchain? - Updated 2017

What is the simplest implementation of the blockchain? Thinking about selling your online business? Not all businesses are built to sell. Contact us for a free market ready assessment of your business. It's not secure and no longer maintained but it showcases most of the common data structures (blocks, transactions, merkle trees, ...) and algorithms (hash cash, retargeting, ...) required to implement a blockchain. In its essence blockchain technology takes away the need for trust - which is at the very core of the banking and financial services: we deposit monies with banks because we trust them we borrow money from them because we trust them - that they will behave according to the law - not like say loan sharks we know if there are problems they will generally do the right thing As a result, if trust can be replaced by technology that everyone trusts it has the potential to reduce the role of banks, lawyers, auditors, accountants. A very simple example of the power of the blockchain can be seen from my own personal experience. I live in Sydney, Australia but am from the UK orignally. I still have cash in my UK bank accounts. It is quicker for me to fly over to the UK (24 hour flight), go to my bank, draw the funds out and fly back than it is to receive funds using the global banking system currently. Instead they take 3 days, charge me $50 for the privilege and give me an exchange rate 2.5% - 4% below market rate! With crytpocurrencies the funds can be transferred and cleared in less than 1 hour and the fees typically cents. (there are exchange rates to get into and out of bitcoin - about 1.6% altogether). This is the tip of a very deep, powerful iceberg The global banking infrastructure requires corresponding banks to work together and to trust each other. (image fr Continue reading >>

From What Is Blockchain? To Building A Blockchain In Less Than Anhour

From What Is Blockchain? To Building A Blockchain In Less Than Anhour

Investor, writer, and emerging tech enthusiast | www.lstephanian.com From What is Blockchain? to building a blockchain in less than anhour A blockchain is a digital ledger of records thats arranged in chunks of data called blocks. These blocks then link with one another through a cryptographic validation known as a hashing function . Linked together, these blocks form an unbroken chain a blockchain. The reason that this type of data structure is useful for things like cryptocurrencies is decentralization, meaning the records inside this chain arent stored in any single location, are accessible by everyone, and are immutable by any one party. Centralized Structure Vs. Decentralized Structure, Source: SoftwareAdvice Although blockchain is most commonly associated with Bitcoin, there are many uses for this technology. There are several broad categories of blockchain applications, a couple of which include: The Blockchain that makes up Bitcoin sends money globally to individuals and merchants. But Blockchains can also create digital assets like stocks and bonds. A Blockchain can create a verifiable record of any data, file, or contract. This can be useful in any industry that uses big data, like the medical industry or government. Before you begin, I should note that this article assumes you have a basic understanding of programming and some understanding of computer science theory. This article isnt meant to be all-encompassing, but rather to serve as an introduction to blockchain programming for those looking to expand their technical knowledge. I believe that the best way to truly understand a concept is to put it into practice. If you are interested in learning how to implement a blockchain contract, Ive put together an easy-to-follow, step-by-step tutorial below. You Continue reading >>

Creating Your First Blockchain With Java. Part1.

Creating Your First Blockchain With Java. Part1.

pineapple express, star trek, late night programming, Desperados ( with lime ) & looking beyond 22338618. Creating Your First Blockchain with Java. Part1. The aim of this tutorial series, is to help you build a picture of how one could develop blockchain technology. Create your first (very) basic blockchain. Implement a simple proof of work ( mining ) system. ( I will assume you have a basic understanding of Object Oriented Programming ) Its worth noting that this wont be a fully functioning, ready for production block chain. Instead this is a proof of concept implementation to help you understand what a blockchain is for future tutorials. You can support this and future tutorials:) We will be using Java but you should be able to follow along in any OOP language. Ill be using Eclipse but you can use any new fancy text editor ( though youll miss out on a lot of good bloat ). Dont worry if your eclipse looks different to mine. Ill be using a dark theme in eclipse because^ Optionally, you can grab GSON library by google (who are they???). This will allow us to turn an object into Json \o/. Its a super useful library that we will also be using further down the line for peer2peer stuff, but feel free to use an alternate method. In Eclipse create a (file > new > ) Java project. Ill call my Project noobchain and create a new Class by the same name (NoobChain). Dont be copying my project name now ( ) A blockchain is just a chain/list of blocks. Each block in the blockchain will have its own digital signature, contain digital signature of the previous block, and have some data ( this data could be transactions for example ). Each block doesnt just contain the hash of the block before it, but its own hash is in part, calculated from the previous hash. If the previous blocks data Continue reading >>

The Blockchain Explained To Web Developers, Part 1: The Theory

The Blockchain Explained To Web Developers, Part 1: The Theory

The Blockchain Explained to Web Developers, Part 1: The Theory The blockchain is the new hot technology. If you haven't heard about it, you probably know Bitcoin. Well, the blockchain is the underlying technology that powers Bitcoin. Experts say the blockchain will cause a revolution similar to what Internet provoked. But what is it really, and how can it be used to build apps today? This post is the first in a series of three, explaining the blockchain phenomenon to web developers. We'll discuss the theory, show actual code, and share our learnings, based on a real world project. To begin, let's try to understand what blockchains really are. Although the blockchain was created to support Bitcoin , the blockchain concept can be defined regardless of the Bitcoin ecosystem. The literature usually defines a blockchain as follows: A blockchain is a ledger of facts, replicated across several computers assembled in a peer-to-peer network. Facts can be anything from monetary transactions to content signature. Members of the network are anonymous individuals called nodes. All communication inside the network takes advantage of cryptography to securely identify the sender and the receiver. When a node wants to add a fact to the ledger, a consensus forms in the network to determine where this fact should appear in the ledger; this consensus is called a block. I don't know about you, but after reading these definitions, I still had troubles figuring out what this is all about. Let's get a bit deeper. Decentralized peer-to-peer networks aren't new. Napster and BitTorrent are P2P networks. Instead of exchanging movies, members of the blockchain network exchange facts. Then what's the real deal about blockchains? P2P networks, like other distributed systems, have to solve a very dif Continue reading >>

A Blockchain In 200 Lines Ofcode

A Blockchain In 200 Lines Ofcode

I like programming and Careless Whisper. The basic concept of blockchain is quite simple: a distributed database that maintains a continuously growing list of ordered records. However, it is easy to get mixed up as usually when we talk about blockchains we also talk about the problems we are trying to solve with them. This is the case in the popular blockchain-based projects such as Bitcoin and Ethereum . The term blockchain is usually strongly tied to concepts like transactions , smart contracts or cryptocurrencies . This makes understanding blockchains a necessarily harder task, than it must be. Especially source-code-wisely. Here I will go through a super-simple blockchain I implemented in 200 lines of Javascript called NaiveChain . The first logical step is to decide the block structure. To keep things as simple as possible we include only the most necessary: index, timestamp, data, hash and previous hash. The hash of the previous block must be found in the block to preserve the chain integrity The block needs to be hashed to keep the integrity of the data. A SHA-256 is taken over the content of the block. It should be noted that this hash has nothing to do with mining , since there is no Proof Of Work problem to solve. To generate a block we must know the hash of the previous block and create the rest of the required content (= index, hash, data and timestamp). Block data is something that is provided by the end-user. A in-memory Javascript array is used to store the blockchain. The first block of the blockchain is always a so-called genesis-block, which is hard coded. At any given time we must be able to validate if a block or a chain of blocks are valid in terms of integrity. This is true especially when we receive new blocks from other nodes and must decide whe Continue reading >>

What Is A Smart Contract? Auto Enforceable Code - Blockchain

What Is A Smart Contract? Auto Enforceable Code - Blockchain

A smart contract can formalize the relationships between people, institutions and the assets they own. The transaction rulesets (agreement) of the smart contract define the conditions rights and obligations to which the parties of a protocol or smart contract consent. It is often predefined, and agreement is reached by simple opt-in actions. This transaction rule set is formalized in digital form, in machine-readable code (formalization). These rights and obligations established in the smart contract can now be automatically executed by a computer or a network of computers as soon as the parties have come to an agreement and met the conditions of the agreement (enforcement) (Glatz). The concept of a smart contract is not new. However, Blockchain seems to be the catalyst for smart contract implementation. The most primitive form of a smart contract is a vending machine. The rules of a transaction are programmed into a machine. You select a product by pressing a number related to that product, insert the coins, the machine acts as a smart contract checking wether you inserted enough money, If yes, the machine is programmed to eject the product, and if you inserted too much money, it will also eject the change. If you didnt insert enough money, or if the machine ran out of the money, you will get your change back. Automatic vending machines not only slashed transaction costs by making human vendors obsolete, but they also expanded service, offering 24/7 availability instead of limited opening hours of a kiosk. Smart contracts are capable of tracking performance in real time and can bring tremendous cost savings. Compliance and controlling happen on the fly. In order to get external information, a smart contract needs information oracles , which feed the smart contract wit Continue reading >>

Build A Blockchain With C++

Build A Blockchain With C++

So, you might have heard a lot about something called a blockchain lately and wondered what all the fuss is about. A blockchain is a ledger which has been written in such a way that updating the data contained within it becomes very difficult, some say the blockchain is immutable and to all intents and purposes theyre right but immutability suggests permanence and nothing on a hard drive could ever be considered permanent. Anyway, well leave the philosophical debate to the non-techies;youre looking for someone to show you how to write a blockchain in C++, so thats exactly what Im going to do. Before I go any further, I have a couple of disclaimers: This tutorial is based on one written by Savjee using NodeJS; and Its been a while since I wrote any C++ code, so I might be a little rusty. The first thing youll want to do is open a new C++ project, Im using CLion from JetBrains but any C++ IDE or even a text editor will do. For the interests of this tutorial well call the project TestChain, so go ahead and create the project and well get started. If youre using CLion youll see that the main.cpp file will have already been created and opened for you; well leave this to one side for the time being. Create a file called Block.h in the main project folder, you should be able to do this by right-clicking on the TestChain directory in the Project Tool Window and selecting: New > C/C++ Header File. Inside the file, add the following code (if youre using CLion place all code between the lines that read#define TESTCHAIN_BLOCK_H and #endif): Continue reading >>

Java Code Examples

Java Code Examples

*OnlyoneBlockchainobjectiscreatedperinstanceofthedaemon.ItkeepstrackofALLpossiblechains,andinternallyhandleschainreorganization. *ThedecisiontoputLedgerManagerasanobjectownedbyBlockchainwasforpurposesofsimplicity--there'sonlyoneBlockchain,andonlyoneLedgerManager. *TheBlockchainhasforkmanagementintegrated,andshouldbeabletoappropriatelyhandleanyunexpectedcircumstances.Forkmanagementisoneof *themajorthingsI'mwatchingforduring2.0.0a1.Ifyouwanttotrytoforkthenetwork,pleasedo.I'msurethereareways. *Astheblockchainhasthemostup-to-dateinformationaboutblockchaindata,itmakesperfectsensefortheledger,whichisbasedpurelyontheblockchain, *tobemanagedbytheBlockchainobject.InitialplansweretohaveseparateBlockchainobjectsforeachforkinachainbuttheoverheadofcloningBlockchain *objectsseemedunwarranted.Significantoptimizationstillneedstobedoneontheforkmanagement--climbingallthewaydowntheshorterchainandbackup *thelongerchainisNOTapermanantsolution,andIhopetohaverespectableforkmanagementoverheadby2.0.0a2. *Additionally,thereisnoneedtostoreidenticalblocksbetweenmultipleforks.Theoverheadofaforksuddenlyrequiringdoubletheblockchainstorageis *unacceptable.Itworks,Ithink.Butunacceptableforproductioncode,sothat'llcertainlychange,hopefullyby2.0.0a2or2.0.0a3,dependingonmyschedule. *Asblocksareaddedtotheblockchain,theledgerisupdated.Whileworkingbeautifullyinsmall-scaletesting,I'msurethesignaturecountsynchronization *betweensignedtransactionsandblockswilltripupatsomepoint,andsendtheBlockchainobjectintoeitheraloopofdispair,oranirrecoverableerror. *Faulttolerancewithdesynchronizationbetweenledgerandblockchainforsignatureaccountswillbea2.0.0a3or2.0.0a4feature.I'vegottathinklongand *hardaboutthebestapproachesthatdon'tcompromisesecurityinthenameoffault-tolerance,whileremainingusable,reliable,andfast. *You'llnot Continue reading >>

Building Your Own Blockchain In R

Building Your Own Blockchain In R

Everybody is freaking out about the rise of the Bitcoin and the potential of the Blockchain technologies. The advent of cryptocurrencies, game changing use cases, disruption of established business models by disintermediation, etc.. By the time Im writing this article, there are more than 1300 crypto-currencies listed in coinmarketcap .. And a lot more coming with the next ICOs (Internet Coin Offering). Most certainly, the main enabler of Bitcoin and of many other currencies (although not all of them) is the Blockchain technology. Although the original paper from Satoshi explains very well the ground idea behind this technology, nothing like creating your own blockchain to fully understand how it works, its limitations and potential improvements (aka If you can code it, you certainly understand it). In this post Id like to share a gentle coding exercise in R (#rstats). Why R? Just because its my favorite language I wouldnt choose R for a productive, full-fledge block chain implementation, but again, this is not the purpose of this post. This is just a learning exercise hacked quite quickly without any aspiration of ever running this code in a productive environment, and should be understood as such. For convenience, I stored the code in a git repository , for others to improve, re-use, try, etc. First things first: what is what in a Blockchain A blockchain is an immutable chain of sequential records or blocks that are chained together using hashes. Blocks can be understood as containers, typically of transactions, but it can be extended to documents, etc. We can think of a blockchain as a database where new data is stored in blocks, that are added to an immutable chain based on all other existing blocks. Blockchain is often referred as a digital ledger of transactions Continue reading >>

How Do Ethereum Smart Contracts Work?

How Do Ethereum Smart Contracts Work?

Like many ideas in the blockchain industry, a general confusion shrouds so called 'smart contracts'. A new technology made possible by public blockchains, smart contracts are difficult to understand because the term partly confuses the core interaction described. While a standard contractoutlines the terms of a relationship (usually one enforceable by law), a smart contract enforces a relationship with cryptographic code. Put differently, smart contracts are programs that execute exactly as they are set up to by their creators. First conceived in 1993, the idea was originally described by computer scientist and cryptographer Nick Szabo as a kind of digital vending machine. In his famous example , he described how users could input data or value, and receive a finite item from a machine, in this case a real-world snack or a soft drink. In a simple example, ethereum users can send 10 ether to a friend on a certain date using a smart contract (Seeour guide" What is Ether? "). In this case, the user would create a contract, and push the data to that contract so that it could execute the desired command. Ethereum is a platform thats built specifically for creating smart contracts. But these new tools arent intended to be used in isolation. It is believed that they can also form the building blocks for 'decentralized applications' (See: " What is a Dapp? ")and even whole decentralized autonomous companies (See:" What is a DAO? ') Its worth noting that bitcoin was the first to support basic smart contracts in the sense that the network can transfer value from one person to another. The network of nodes will only validate transactions if certain conditions are met. But, bitcoin is limited to the currency use case. By contrast, ethereum replaces bitcoin's more restrictive langu Continue reading >>

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