#solidity

“Bankers Rounding” for Smart Contracts
▻https://hackernoon.com/bankers-rounding-for-smart-contracts-2bccd0b664?source=rss----3a8144eabf

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Hello everyone! My name is Anton, and I’m the CTO at crypto.tickets. Crypto Tickets has developed the new decentralized ticketing protocol that protects tickets from being counterfeited or double sold. The appeals of Crypto Tickets for event organizers are the abilities to control the secondary market, retain extra commissions on every ticket resale, prohibit resales entirely, or allow resales only for authorized fans. This technology is designed to be an add-on for any ticket selling technology on the market.Integers?As you know, #ethereum smart contracts can’t handle real (floating point) numbers easily. So, we all work with integers.Still, if you work with percentages, you will have to divide one number by another. That’s where rounding comes in. For example, imagine you need to send (...)

#blockchain #smart-contracts #solidity #bankers-rounding

#programming Languages for Blockchain Solutions Developing
▻https://hackernoon.com/programming-languages-for-blockchain-solutions-developing-69df215147af?s

Blockchain is becoming so popular that finally, we can safely say: technology has emerged from the “cryptocurrency boom” shadow. Today, news headlines are increasingly filled with messages about the technology distributed registry implementation in one or another area. Such success attracts the developers` attention of course. At the same time, the demand for professionals continues to grow. For example, according to the LinkedIn investigation, over the past year in the US need to blockchain developers has increased in 33 (!) Times.If you are ambitious to break into the rating of top blockchain gurus, but still only at the beginning of your career, it is worth understanding the most popular programming languages, their advantages, and disadvantages, as well as to learn about their (...)

#coding #golang #solidity #javascript

Exploding rockets & millions of free tokens? Let’s take a good look at integer overflows.
▻https://hackernoon.com/exploding-rockets-millions-of-free-tokens-lets-take-a-good-look-at-integ

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Exploding rockets & millions of free #blockchain tokens? — It’s time we took a GOOD LOOK at integer overflows.Integer overflows are a tricky beast! This article is your free ticket, not just to understanding integer overflows but, to discovering new preventative measures.If you are not a software developer, please read on, integer overflows are fascinating. Also, I have worked really hard to make this article easy to digest; the maths and coding are on the light-and-easy side, so have a little fun.If you are a software developer, stick around until the end, because you will get a chance to deploy your very own smart contract on a blockchain. It’s fast and it’s free!RustWe are going to start off this article by providing you with a few, easy to understand, demonstrations; written in #rust. (...)

#integer-overflow #solidity #cybermiles

Beyond #solidity, part 1: Setting up the #monorepo
▻https://hackernoon.com/beyond-solidity-part-1-setting-up-the-monorepo-8db094ebbee5?source=rss--

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After developing the smart contracts for 8x, I thought it was all over. That was far from the truth. The requirements for a decentralized protocol are slowly increasing over time with the need for:An easy to use JS libraryUp to date place of contract addresses and ABIsDocumentation (dynamic, because who actually updates static documentation)Developer utilitiesdApp/widget to interact with the underlying protocolMarketing website that integrates or includes your dApp/widgetEach of these requirements, more or less, requires its own repo. Before you know it you’ll be managing over 7 different repos with version control on each of them. Suddenly, making a small change in one package will require an npm install in at least another 2 packages (best case).So what’s the answer to this madness? A (...)

#developer #javascript #setting-up-the-monorepo

Hands On: Creating Your Own Local Private Geth Node (Beginner Friendly)
▻https://hackernoon.com/hands-on-creating-your-own-local-private-geth-node-beginner-friendly-3d4

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Source: ▻https://altcointoday.com/If you’re new to the blockchain sphere and want to get a hands-on feel of this ground-breaking yet a-tad-bit arcane #technology, this tutorial is for you.This will be a comprehensive step-by-step tutorial for you to get started with #ethereum blockchain. So, don’t worry I will cover each and every step.Source: ▻https://tenor.com/What will we build?A local testnet Ethereum blockchain using Geth.Local: This blockchain will be running only on your computer (formally, node) locally.Testnet: This will not mine real Ethers. Only fake ones. It is perfect for testing dApps, or for just playing around.PrerequisitesMacOSHomebrew (Download link: ▻https://brew.sh/)XCode (Get from AppStore)Setting Up Development EnvironmentStep 0: Download Geth using HomebrewFire up your (...)

#bitcoin #solidity #javascript

Upgradeable #ethereum Contracts V2
▻https://hackernoon.com/upgradeable-ethereum-contracts-v2-786d9c18cd9d?source=rss----3a8144eabfe

Getting the most out of delegatecallLooking for the code?I’m a blockchain architect and developer at Design is Dead, check us out!A couple of months ago I wrote my first blog post about upgradeable smart contracts on the Ethereum blockchain. We explained that once a smart contract has been deployed onto the blockchain it cannot be changed (Ethereum currently does not have block finality, so this is probabilistic).Wait? Not being able to upgrade code after launching it? That seems like a bad idea, especially if you’re used to an agile development cycle. And while guaranteed code execution can be a benefit, when there is a bug it is the total opposite. Bugs in smart contracts have caused millions of dollars in losses and even gave birth to Ethereum as we know today, after one of the most (...)

#ethereum-contracts-v2 #upgradeable-contracts #smart-contracts #solidity

Compile #solidity Smart Contracts Faster in Truffle Projects
▻https://hackernoon.com/compile-solidity-smart-contracts-faster-in-truffle-projects-eb8bebb61ec3

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The Truffle Suite is the most widely used #development framework for Solidity development but it is not perfect. We at Polymath, deal with a large set of interconnected smart contracts.And adding more contracts everyday :)The sheer number of smart contracts cause the compilation time to go over 80 seconds on my daily driver. Lucky for us, we can make the compilation go faster.Truffle uses solc.js by default rather than native binaries for the compilation of smart contracts. solc.js offers greater portability but is significantly slower than natively compiled binaries.How much faster are the native binaries, you may ask? I managed to cut down Polymath-core’s compilation time from 80 seconds to just under 15 seconds!It’s that fast!Why doesn’t everyone already use native binaries? Managing (...)

#blockchain-development #blockchain #ethereum

Smart Contracts on Steroids: Solving the Problems Facing #ethereum’s #solidity
▻https://hackernoon.com/smart-contracts-on-steroids-solving-the-problems-facing-ethereums-solidi

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flickrThe Ethereum network currently consists of more than 1,700 decentralized applications (DApps), a number that is expected to grow in the coming years. And while all of these DApps rely on smart contracts to accomplish a number of important tasks, it has become clear that smart contracts are prone to errors, bugs and other catastrophic mistakes — to the tune of more than a billion dollars stolen in smart contract hacks to-date.In order to write a smart contract, programmers must learn an entirely new programming language called “Solidity.” While smart contracts facilitate complex operations in ethereum, making simple mistakes while writing smart contracts in Solidity can cause dire consequences, including security breaches and / or very high transactional costs.One of the most (...)

#ethereum-solidity #blockchain #smart-contracts

#hackpedia: 16 #solidity Hacks/Vulnerabilities, their Fixes and Real World Examples
▻https://hackernoon.com/hackpedia-16-solidity-hacks-vulnerabilities-their-fixes-and-real-world-e

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A Complete List of all Solidity Hacks/Vulnerabilities, their Fixes and Real World Hack ExamplesAlthough in its infancy, Solidity has had widespread adoption and is used to compile the byte-code in many Ethereum smart contracts we see today. There have been a number of harsh lessons learnt by developers and users alike in discovering the nuances of the language and the EVM. This post aims to be a relatively in-depth and up-to-date introductory post detailing the past mistakes that have been made by Solidity developers in an effort to prevent future devs from repeating history.If you want to add something or have traced some error then you can submit a pull request here.Here are 16 interesting hacks:1. Re-EntrancyOne of the features of Ethereum smart contracts is the ability to call and (...)

#solidity-vulnerabilities #solidity-security #solidity-hacks

Arrays in #solidity
▻https://hackernoon.com/arrays-in-solidity-b65c1326f48b?source=rss----3a8144eabfe3---4

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This is the second Aventus technical blog on Solidity from Alex Pinto, a recent addition to our blockchain engineering team. You can read his first post on Working with Strings in Solidity.There are many occasions when we want to pass to a function a group of similar data that may, or may not, be limited in number. The most basic data type for this situation is an array (and in several cases, this can be used to implement more advanced data structures). We can pass and return arrays without problems, as the following illustrates.The above uses arrays of uint, which represents a 256-bit integer, of unlimited size. That means I can pass any array of the correct type into the function. It also means I have to initialise the return array in getArrayMultipliedByScalar before I can use it, (...)

#ethereum #ticketing #arrays-in-solidity #programming

Your “private” #solidity Variable is Not “private.” Save it before it becomes Public
▻https://hackernoon.com/your-private-solidity-variable-is-not-private-save-it-before-it-becomes-

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One of the most Common but Unheard Issues with EthereumIf you have worked with #ethereum then you must have written smart contracts, and thus most probably used the keyword private . It seems like it does its work well. Right? Well, actually not.Anyone in this world with a blockchain explorer can see your so called private variables.Sounds ridiculous, but yes its true. Let’s see how to hack a contract.▻https://medium.com/media/3a7f379e550e01f53629778334342f97/hrefLet’s take a vulnerable contract.▻https://medium.com/media/f1722686fc7a175f1cafad2727ac960f/hrefIt’s basically a game: an odd-even multiplayer game contract, which chooses the winner based on the numbers guessed. Each player chooses a number and if the sum is even then the first player wins, otherwise the second player wins.The game (...)

#solidity-issues #private-solidity-variable #privatevariable

#ethereum Smart Contract #upgradeability: Hands-On
▻https://hackernoon.com/ethereum-smart-contract-upgradeability-hands-on-ceaf98be070f?source=rss-

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Just like with every new material, understanding smart contract upgradeability requires to spent quality time on it. Let’s try to shorten this learning curve :)Lately great articles and resources have been published on the topic and the Zeppelin team (OpenZeppelin and zeppelinOS) really pushed forward the concept of #upgradeable smart contracts.However I am feeling that a dead simple example is missing in those discussions and that is what I would like to share with you.I am not going to summarizes or give you an overview about upgradeability patterns here. As I said I think there is already enough amazing ressources on the internet and you will need to spend time learning and searching anyway (this is a amazing starting post). Nevertheless I would like to provide you with an easy start (...)

#smart-contracts #solidity

From A to Z: Making the #mvp of a real DApp on #ethereum and deploying it
▻https://hackernoon.com/from-a-to-z-making-the-mvp-of-a-real-dapp-on-ethereum-and-deploying-it-5

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A month ago, I finished writing the Ethereum development walkthrough tutorial series, with the last part being a how-to make a DApp. While it concluded that tutorial series well enough and could serve as a solid starting point, I still thought it could be far more interesting to make a tutorial on how to make a full DApp, from start to finish, and share not only the code, but also the experience to get it running on the Ethereum’s main network.You can find that DApp here, its github repos here and here. It’s on all accounts a real DApp deployed on the Ethereum main net, and we’ll try to dissect its development together.Kick offAs a project, making a decentralized application on Ethereum is not really different from making a classic, centralized one, beside the fact that more care should (...)

#dapp-mvp-ethereum #solidity #dapps

Problems & Costs of Smart Contract Development
▻https://hackernoon.com/problems-costs-of-smart-contract-development-e86e9446ba9e?source=rss----

Can your business afford it?Image by Gratisography.comThe problem with smart contracts is that most small and medium businesses are unable to implement smart contracts not only due to technological complexity but mostly because of their expensiveness. The costs for smart contract development are skyrocketing as there is an increasing demand for smart contract developers and contracts for ICOs.Why smart contracts are so great in the first place?Smart contracts, which are, actually, a self-executing code on #blockchain that automatically implements the terms of an agreement between parties or business logic. It’s basically an unbreakable agreement with predefined rules. In addition, smart contracts are deterministic which means the same output will be generated from a given initial (...)

#solidity #ethereum #blockchain-technology #ethereum-blockchain

Exposé technique « Développer un contrat/programme sur Ethereum »

Le 2 juillet, au festival Pas Sage en Seine / Hacker Space Festival #PSESHSF, j’ai eu le plaisir de faire un exposé sur la #chaîne_de_blocs #Ethereum, plus précisement sur l’écriture de programmes (on dit parfois contrats) Ethereum. Cet exposé s’adresse donc surtout aux programmeurs.

▻http://www.bortzmeyer.org/pas-sage-en-seine-ethereum.html

#Solidity

Valider qu’un contrat Ethereum est bien ce qu’il prétend être

La #chaîne_de_blocs #Ethereum permet bien plus que de gérer de l’argent : elle autorise la création de programmes (appelés contrats) qui peuvent être invoqués par des utilisateurs, qui envoient leur argent au contrat, espérant que celui-ci va bien faire ce qui est promis. Mais comment le vérifier ?

►http://www.bortzmeyer.org/valider-contrats-ethereum.html

#programmation #Solidity #vérification_de_programmes #blockchain

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