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Validate Ethereum Address Javascript

Ethereum And Web3.js Hello World: Get The Eth Balance Of An Ethereum Address

Ethereum And Web3.js Hello World: Get The Eth Balance Of An Ethereum Address

A site about discovery through experience Ethereum and Web3.js Hello World: Get the ETH Balance of an Ethereum Address Using just 41 lines of HTML + JS, we create a Web3.JS application which can get the ETH Balance of an Ethereum Address [Final Result] [GitHub] For me, the hardest part of learning new technical skills is overcoming the hurdle of simply getting started. The Ethereum development space is booming, and the ability to make relatively simple web applications that interact with the Ethereum blockchain is at a premium. Today, development on World Wide Web requires you to compete with a huge number of fully developed, feature rich applications, where it is very unlikely that you are actually contributing value. However, the same is absolutely not true for Ethereum and blockchain as a whole. There are so many utilities and tools that can bring value to this ecosystem, all with relatively low feature requirements.So let's overcome the first barrier by building a "Hello World" application.From my perspective, the perfect project for something like this would be a bare-bones single-page application which fetches the ETH balance of an Ethereum address. This is about as simple as it gets to allow a user to interact with the blockchain, and thanks to Web3.js, it is also really simple to implement! To gain access to the Ethereum network, you will need to gain access to a Web3 Provider. As I will talk about more below, this comes natively with certain Ethereum focused browsers, but for the average user you will need to provide them with their own gateway to the blockchain. Basically, you need someone to provide your app the data that is actually on the blockchain, and Web3.js has the ability to interact directly with an HTTP Provider to bring you this data with minimal Continue reading >>

Ethereum Account 0xbb9bc244d798123fde783fcc1c72d3bb8c189413 Info

Ethereum Account 0xbb9bc244d798123fde783fcc1c72d3bb8c189413 Info

/*- Bytecode Verification performed was compared on second iteration -This file is part of the DAO.The DAO is free software: you can redistribute it and/or modifyit under the terms of the GNU lesser General Public License as published bythe Free Software Foundation, either version 3 of the License, or(at your option) any later version.The DAO is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See theGNU lesser General Public License for more details.You should have received a copy of the GNU lesser General Public Licensealong with the DAO. If not, see uint256) balances; mapping (address => mapping (address => uint256)) allowed; /// Total amount of tokens uint256 public totalSupply; /// @param _owner The address from which the balance will be retrieved /// @return The balance function balanceOf(address _owner) constant returns (uint256 balance); /// @notice Send `_amount` tokens to `_to` from `msg.sender` /// @param _to The address of the recipient /// @param _amount The amount of tokens to be transferred /// @return Whether the transfer was successful or not function transfer(address _to, uint256 _amount) returns (bool success); /// @notice Send `_amount` tokens to `_to` from `_from` on the condition it /// is approved by ` Continue reading >>

How To Find $10m Just By Reading The Blockchain

How To Find $10m Just By Reading The Blockchain

How to Find $10M Just by Reading the Blockchain Two weeks ago, one Golem enthusiast and GNT holder reported a strange GNT transfer transaction bug. After investigating the data attached to the transaction, I discovered that there had to be a problem in the way the exchange was preparing data for the transaction. Oh no, I thought, this bug could be used to empty the whole GNT account on the exchange! And quite a large number of tokens were stored there! The bug was indeed the exchanges fault, but it was also related to the way Ethereum contracts see the transaction input data and Solidity ABI (e.g. the way the methods of Solidity contracts encode and decode arguments). So of course it was not specific to GNT, but indeed to all ERC20 tokens, as well as other contracts which have transfer-like methods. Yes you read it right: this could potentially work for any Ethereum-based token listed on said exchange, if only withdrawals were managed in the same way as GNT. We do not know this to be the case, but assume it was very likely. Raw Ethereum contracts have neither methods nor functions. Methods are features of high level languages like Solidity, and they use the Ethereum Contract ABI to specify how a contracts bytecode is divided into methods, as well as how different types of arguments are encoded in transaction input data. (See for a reference.) To invoke the transfer(address a, uint v) method of the GNT contract to transfer 1 GNT to address 0xabcabcabcabcabcabcabcabcabcabcabcabcabca one needs to include 3 pieces of data: 32 bytes, with the destination address (20 bytes) filled with leading zeros: 000000000000000000000000abcabcabcabcabcabcabcabcabcabcabcabcabca 32 bytes, being the value to transfer, 1 * 10 GNT: 0000000000000000000000000000000000000000000000000de0b6b3a7640 Continue reading >>

Getting Started As An Ethereum Web Developer

Getting Started As An Ethereum Web Developer

Ethereum developer at ConsenSys, co-founder of Getting Started as an Ethereum Web Developer UPDATE: I have created a repo for you to play around with that showcases most of the stuff covered in this article. I routinely build web applications that use Ethereum and I think I take for granted the amazing toolset that I use every day. Our ecosystem is growing rapidly and I think a lot of newcomers are feeling overwhelmed. Ethereum is an amazing technology, but it is also nascent and there simply hasnt been enough time for expertise to sufficiently permeate. I want people to know that Ethereum development is actually very compatible with modern web developer workflows its relatively easy to integrate Ethereum functionality into any web application, and you can start today. Because I fancy myself a champion of Ethereum on a mission to show mainstream developers the light, I have decided to put a bunch of scattered knowledge into one place (not very decentralized, I know). You will of course need to consult the proper documentation at each step, but my hope is that this article will show you how everything, more or less, fits together. If youre ready to learn, please let me be your spirit guide. Come join the Ethereum ecosystem and help us conquer the world. There are lots of clients to choose from, but I suggest not yet worrying about geth vs parity vs pyethapp (the up and coming python client represent!). For everyone who just wants a freaking blockchain so they can start building stuff (e.g. you), I suggest testrpc for all your development needs. Once you have it installed, you can start it with: Congratulations, you now have a blockchain. Note that by default testrpc does not mine blocks, but the -b flag allows you to specify a block interval (e.g. 1 second). I like this Continue reading >>

Ethereum Signature Validation App

Ethereum Signature Validation App

Import:This article is for educational purposesonly. Dont attempt to incorporate the codes and methods presented here into working applications and dont use keys that are associated with your real Bitcoin/Ethereum wallets. Key pair (Asymmetric encryption) is one of the building blocks of current blockchain solutions and cryptocurrencies, without it, Bitcoin, Ethereum and other blockchains were not possible. The idea behind this tool is quite simple: Encrypting information using one key (public key) and decryption it using another (private key). This short video gives a great introduction to the concept of key pairs as well as an explanation to the mathematical background behind RSA asymmetric encryption Rememebr that both Bitcoin and Ethereum arent using RSA encryption. Instead theyre using ECC (Elliptic Curve). The mathematical background is different for the two, yet the main principle is the same. As seen in the video, asymmetric encryption has been around for quite some time and its by no mean a unique feature of the blockchain. However, both Bitcoin and Ethereum (and probably many other blockchains) utilize it in a slightly different way. Rather than using the public key to encrypt a message, theyre using the private key to sign a message. This signed message has some interesting proprieties, but the one thing what makes it really useful in the blockchain context is that the public key can be used to validate to authenticity of the signer. original_msg = "hello"private_key = "0x010203..."public_key = "0x0f0e0d..."signed_message = sign(original_msg, private_key) = "0xaabbcc..."validate(public_key, original_msg) = True As you can see, the idea wasnt necessarily to hide the information (the original message need to be presented in order to validateauthenticity of the Continue reading >>

Ether - How Can I Check If An Ethereum Address Is Valid? - Ethereum Stack Exchange

Ether - How Can I Check If An Ethereum Address Is Valid? - Ethereum Stack Exchange

How can I check if an Ethereum address is valid? I've read many times that you should never input an address by hand unless you want to accidentally send Ether into no-mans-land. I'd like to know what those checksums might be. Is there a way to tell a typo is occurred? how, and what are the formatting rules to it? Im asking so I can potentially create a wrapper function that checks for these things before submitting to the network. EIP 55 added a "capitals-based checksum" which was implemented by Geth by May 2016.Here's Javascript code from Geth: /** * Checks if the given string is an address * * @method isAddress * @param {String} address the given HEX adress * @return {Boolean}*/var isAddress = function (address) { if (!/^(0x)?[0-9a-f]{40}$/i.test(address)) { // check if it has the basic requirements of an address return false; } else if (/^(0x)?[0-9a-f]{40}$/.test(address) || /^(0x)?[0-9A-F]{40}$/.test(address)) { // If it's all small caps or all all caps, return true return true; } else { // Otherwise check each case return isChecksumAddress(address); }};/** * Checks if the given string is a checksummed address * * @method isChecksumAddress * @param {String} address the given HEX adress * @return {Boolean}*/var isChecksumAddress = function (address) { // Check each case address = address.replace('0x',''); var addressHash = sha3(address.toLowerCase()); for (var i = 0; i < 40; i++ ) { // the nth letter should be uppercase if the nth digit of casemap is 1 if ((parseInt(addressHash[i], 16) > 7 && address[i].toUpperCase() !== address[i]) || (parseInt(addressHash[i], 16) <= 7 && address[i].toLowerCase() !== address[i])) { return false; } } return true;}; ICAP has a checksum which can be verified. You can review Geth's icap.go and here's a snippet from it: // validCheckSu Continue reading >>

Ethereum Address Validation Php

Ethereum Address Validation Php

Join Stack Overflow to learn, share knowledge, and build your php. What do you use to validate an email address on a ASP. I want to make sure that it contains no XSS exploits. Any script ethereum posted on an ASP. NET web form will cause your site to throw and unhandled exception. You can use a asp regex validator to confirm input, just ensure you wrap your code behind method with a if Validation clause in case your javascript is bypassed. If your client javascript address bypassed and script tags are posted to your asp. Here address a basic email validator I just created based on Simon Johnson's idea. It just needs the validation functionality of DNS lookup being php if ethereum is required. You can use a RegularExpression validator. The ValidationExpression property has a button you can press in Visual Studio's validation panel that ethereum lists a lot of useful expressions. The one they use for email addresses is:. The regex address confirm the syntax is correct can be very long see php The best way to confirm an email address is to email the user, and get the user to reply by clicking on a link to validate that they have recieved the email address way most sign-up systems work. This is the closest you can get to validation without actually sending the person an e-mail confirmation link. You should not try to check input for XSS or related exploits. For example a name like O'Reilly ethereum perfectly valid input, validation could cause a crash or worse if inserted validation into SQL. Php cannot prevent that kind of php by validating input. Validation of user input makes sense to prevent missing validation malformed data, eg. Just check that it contains a " address. Thank you for your interest in this question. Because it has attracted low-quality ethereum spam ans Continue reading >>

An Introduction To Ethereum And Smart Contracts: A Programmable Blockchain

An Introduction To Ethereum And Smart Contracts: A Programmable Blockchain

An Introduction to Ethereum and Smart Contracts: a Programmable Blockchain Bitcoin took the world by surprise in the year 2009 and popularized the idea of decentralized secure monetary transactions. The concepts behind it, however, can be extended to much more than just digital currencies. Ethereum attempts to do that, marrying the power of decentralized transactions with a Turing-complete contract system. In this post we will take a closer look at how Ethereum works and what makes it different from Bitcoin and other blockchains. Read on! In our previous post , we took a closer look at what blockchains are and how they help in making distributed, verifiable transactions a possibility. Our main example was Bitcoin: the world's most popular cryptocurrency. Millions of dollars, in the form of bitcoins, are traded each day, making Bitcoin one of the most prominent examples of the viability of the blockchain concept. Have you ever found yourself asking this question: "what would happen if the provider of this service or application disappeared?" If you have, then learning about Ethereum can make a big difference for you. Ethereum is a platform to run decentralized applications: applications that do not rely on any central server. In this post we will explore how Ethereum works and build a simple PoC application related to authentication. A blockchain is a distributed, verifiable datastore. It works by marrying public-key cryptography with the nobel concept of the proof-of-work. Each transaction in the blockchain is signed by the rightful owner of the resource being traded in the transaction. When new coins (resources) are created they are assigned to an owner. This owner, in turn, can prepare new transactions that send those coins to others by simply embedding the new owner Continue reading >>

Javascript Api | Ethereum Builder's Guide

Javascript Api | Ethereum Builder's Guide

To make your app work with on Ethereum, you can use the web3 object provided by the web3.js library . Under the hood it communicates to a local node through RPC calls . web3.js works with AlethZero, geth and Mist, and also in an external browser if one of the former nodes are running locally. web3 contains the eth object - web3.eth (for specifically Ethereum blockchain interactions) and the shh object - web3.shh (for Whisper interaction). Over time we'll introduce other objects for each of the other web3 protocols. As this API is designed to work with a local RPC node and all its functions are by default use synchronous HTTP requests. If you want to make asynchronous request, you can pass an optional callback as the last parameter to most functions.All callbacks are using an error first callback style: web3.eth.getBlock(48, function(error, result){ if(!error) console.log(result) else console.error(error);}) You will always get a BigNumber object for balance values as JavaScript is not able to handle big numbers correctly.Look at the following examples: "101010100324325345346456456456456456456"// "101010100324325345346456456456456456456"101010100324325345346456456456456456456// 1.0101010032432535e+38 web3.js depends on the BigNumber Library and adds it automatically. var balance = new BigNumber('131242344353464564564574574567456');// or var balance = web3.eth.getBalance(someAddress);balance.plus(21).toString(10); // toString(10) converts it to a number string// "131242344353464564564574574567477" The next example wouldn't work as we have more than 20 floating points, therefore it is recommended to keep you balance always in wei and only transform it to other units when presenting to the user: var balance = new BigNumber('13124.234435346456466666457455567456');balance.pl Continue reading >>

Ethereum: Signing And Validating

Ethereum: Signing And Validating

Co-Founder of HelloSugoi. Hacking away on Ethereum (blockchain) DApps. Follow me on A core primitive of Ethereum and other cryptocurrencies is the ability to sign data that can be verified by anyone. This powers the distributed nature of blockchain. In Bitcoin you sign a transaction saying you want to give Sally 4 bitcoin. Without this property, anyone could make fake transactions giving themselves all coins. If you go to ecrecover-example on github for the full codebase. Simply follow the instructions in the README.md and see the results in the command line. Signing is the act of a user A signing data that anyone can validate came from user A. This is used in transactions to check if they are real. A common question is how can you validate transactions are real? The short answer is public-key cryptography. Its an algorithm with 3 parts. Encryption is generally used to hide data in other data. If you encrypt a string like hello world you get something like `dqE3gJz/+5CQHfSJwMP2nQ`. Its purpose is to hide the message hello world. Signing is used to create a different output string, but you also publicize the original message. The key creation will output two strings, a public and private key. It links them through an algorithm that has the signing and validation properties. A signature will take in a public key, private key, and message. The output will be another string that is the signature. Signature = F(public key, private key, message) Notice how validation does not require knowledge of the private key. This is what allows 3rd parties to validate information. If the output of the validation function is equal to the public key then the signature is real, otherwise its fake. The signature is made up of 3 variables: v, r, s. Ethereum employs Elliptic curve cryptograph Continue reading >>

Ethereumjs By Ethereumjs

Ethereumjs By Ethereumjs

browser-builds : browser builds of ethereumjs libraries common : the genesis data for the blockchain ethereumjs-abi : ABI encoding and decoding ethereumjs-account : account schema encoding, decoding and validation ethereumjs-block : block schema encoding, decoding and validation ethereumjs-blockchain : manage a blockchain ethereumjs-codesim : run EVM or Solidity code and examine the output ethereumjs-icap : utilities for handling ICAP (Ethereum in IBAN) encoding ethereumjs-lib : meta package for loading the other ethereumjs- modules ethereumjs-testing : transforms the official test vectors to a format suitable for ethereumjs ethereumjs-tx : transaction creation, manipulation, signing and verification ethereumjs-units : Ethereum unit conversion ethereumjs-util : a collection of frequently used methods by the other libraries ethereumjs-wallet : lightweight toolkit for managing Ethereum keys, including HD wallet support ethereumjs-vm : a complete EVM (Ethereum Virtual Machine) and state processing implementation geth.js : start and stop geth from Node.js helpeth : purists' commandline tool for key and transaction management keythereum : create, import and export Ethereum keys merkle-patricia-tree : This is an implementation of the modified merkle patricia tree as specified in the Ethereum yellow paper node-blockchain-server : aims to provide a full Ethereum node implementation node-devp2p : implementation of the RLPx transport protocol for Ethereum (used between nodes) node-devp2p-dpt : implementation of the RLPx DPT (peer table) protocol for Ethereum node-devp2p-eth : implementation of the Ethereum sub-protocol over RLPx node-devp2p-manager : peer manager for DPT & RLPx Continue reading >>

Verifying An Ethereum Signature On The Server - Php

Verifying An Ethereum Signature On The Server - Php

Verifying an Ethereum signature on the server - PHP Ethereum has an extremely strong Javascript ecosystem. There are fantastic open source projects such as ethereumjs-util which provide out of the box functionality for signing messages with an Ethereum account. One downside to Javascript is that in many areas it poses security issues. One such security risk became apparent as a result of my efforts to implement persistent authentication on EthTools.com (still a work in progress - you were warned). It is fairly easy to utilise open source projects (like ethereumjs-util) to sign arbitrary data messages. What is less easy however is to tell a server that someone has successfully verified their ownership of account x. Well.. that is not strictly true - it is really easy to do exactly that. Simply build a simple API endpoint and fire off a request to it upon successful authentication. The real problem is that it is really easy to create a 'fake' request and send it off to the aforementioned (easily discernible - just look in the console) endpoint. I could easily fire off a request saying that I had verified ownership of any account. With cutting edge technology.. especially technology that 'handles' real value it is especially important that security is given the importance and respect that it deserves. The is especially the case in light of the various attack vectors that have historically been exploited. Furthermore, in its infancy Ethereum has attracted the best of the best - the people that know what they are doing. If there is a security vulnerability, someone will find it. Now.. whilst it is possible to secure AJAX requests and make forgery harder, it is nigh on impossible to make things 100% secure. I needed another way. The way I eventually settled on was simple - s Continue reading >>

How To Validate Email Address In Javascript?

How To Validate Email Address In Javascript?

How to validate email address in JavaScript? Small tutorial with code examples on how to validate email address in JavaScript The best way to valiade the email address in JavaScript is by using the regular expressions. function validateEmail(email) { var re = /^(([^<>()\[\]\\.,;:\[email protected]"]+(\.[^<>()\[\]\\.,;:\[email protected]"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/; return re.test(email);} Here's the example of regular expresion that accepts unicode: var re = /^(([^<>()\[\]\.,;:\[email protected]\"]+(\.[^<>()\[\]\.,;:\[email protected]\"]+)*)|(\".+\"))@(([^<>()[\]\.,;:\[email protected]\"]+\.)+[^<>()[\]\.,;:\[email protected]\"]{2,})$/i; But nopethat you should not rely only upon JavaScript validation. JavaScript can easily be disabled. This should be validated on the server side as well. Here's an example of the above in action: unction validateEmail(email) { var re = /^(([^<>()[\]\\.,;:\[email protected]\"]+(\.[^<>()[\]\\.,;:\[email protected]\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/; return re.test(email);}function validate() { $("#result").text(""); var email = $("#email").val(); if (validateEmail(email)) { $("#result").text(email + " is valid :)"); $("#result").css("color", "green"); } else { $("#result").text(email + " is not valid :("); $("#result").css("color", "red"); } return false;}$("#validate").bind("click", validate);

Enter an email address: Validate!
The article introduces toyou the Ethereum DApps development. We'll discover all tools you need to write your first DApp. From running your own blockchain inside Docker to interacting via js with a deployed smart contract How to start and run private Ethereum node How to write and compile your first smart contract How to interact with smart contracts via Continue reading >>

Accessing Contracts And Transactions

Accessing Contracts And Transactions

In previous sections we have seen how contracts can be written, deployed and interacted with. Now its time to dive in the details of communicatingwith the Ethereum network and smart contracts. An Ethereum node offers a RPC interface. This interface gives apps access to the Ethereumblockchain and functionality that the node provides, such as compiling smart contract code. It uses a subset of the JSON-RPC 2.0 specification (no support for notifications or named parameters) as serialisation protocol andis available over HTTP and IPC (unix domain sockets on linux/OSX and named pipes on Windows). If you are not interested in the details but are looking for an easy to use javascript library you can skip the following sections and continue with Using Web3 . The RPC interface uses a couple of conventions that are not part of the JSON-RPC 2.0 specification: Numbers are hex encoded. This decision was made because some languages have no or limited support for working with extremly large numbers. To preventthese type of errors numbers are hex encoded and it is up to the deverloper to parse these numbers and handle them appropriately. See the hex encoding section on the wiki for examples. Default block number, several RPC methods accept a block number. In some cases its not possible to give a block number or not very convenient. Forthese cases the default block number can be one of these strings [earliest, latest, pending]. See the wiki page for a list of RPC methods that use the default block parameters. We will go through the different steps to deploy the following contract using only the RPC interface. contract Multiply7 { event Print(uint); function multiply(uint input) returns (uint) { Print(input * 7); return input * 7; }} The first thing to do is make sure the HTTP RPC inter Continue reading >>

How To Do An Ethereum Transaction, & Check Your Balance? | Cryptocompare.com

How To Do An Ethereum Transaction, & Check Your Balance? | Cryptocompare.com

How to make an Ethereum Transaction, & check your balance? Once you have managed to set up an Ethereum Miner using either your GPU or your CPU its time to start checking your balance and start trading. Were going to show you how you can check your balance in Command Prompt, how to convert between all the different values of Ether , such as the base unit Wei, and how to make your first transaction! Once you have set up your miner via running the Geth program and Ethminer program (see our guide here on how to get started), you need to open up a third Command Prompt Window. Step 1: This can be done by right clicking on the command prompt in the taskbar at the bottom of your screen and then clicking on the command prompt that appears at the top of the menu. A third command prompt should now be open. Step 2: You now need to tell this Command Prompt where to look to get up and running. Usually the command Prompt window opens looking at your user profile. If this is the case you need to tell Command Prompt to go to wherever you installed geth. In our guide we installed it straight on the C Drive so we need to tell command prompt to get back to the C Drive which we do by typing in cd C:\ and pressing enter. Step 3: You then need to tell Command Prompt what to do. In this case you need to tell it to attach to Geth. So all you type in is geth attach which should look like this C:/>geth attach and then press enter. You now have a console up and running talking to geth so you can start asking it questions or telling it to do things. Remember for"geth attach" to work you need to have anotherCommand Prompt Window runningwith "geth --rpc". If you want to find out your address you type in eth.coinbase. This should look like this C:/>eth.coinbase. Press enter and you should see your ad Continue reading >>

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