Creating private blockchain on ethereum using r
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Creating private blockchain on ethereum using r
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Content:
- Parkchain: A Blockchain Powered Parking Solution for Smart Cities
- Use Key Management Service (AWS KMS) to securely manage Ethereum accounts: Part 1
- How to Set Up a Private Ethereum Blockchain in 20 Minutes
- How to Create Private Ethereum Blockchain
- Law and the Blockchain
- How to Build a Private Ethereum Blockchain
- Implementing a blockchain from scratch: why, how, and what we learned
- What is blockchain?
Parkchain: A Blockchain Powered Parking Solution for Smart Cities
The concept of blockchain has evolved rapidly way beyond just Bitcoin. We are observing a rapid increase of interest in alternative types of cryptocurrencies and technologies based on the idea of a distributed ledger.
This post assumes basic knowledge of how blockchain works. If you need a quick recap, here are some links:. Ethereum takes these concepts to a new level. While Bitcoin is a distributed ledger where all users agree on cryptocurrency transfers, Ethereum is a distributed ledger where all users agree on code execution and data updates. A distributed application is a piece of code uploaded to the blockchain, and sending transactions is equivalent to executing some public functions exposed by this code.
Miners in the Bitcoin network process " coin transfer " transactions, while miners in the Ethereum network process " function call " transactions. Such function calls can modify application state which is data stored and shared in the ledger. Such apps are called Smart Contracts or dapps decentralized apps. Each code execution needs to be paid by the caller, with dedicated currency called gas. Since each transaction is associated with an Ethereum account, required gas is calculated by converting the ETH cryptocurrency, which can be mined or just bought on exchange markets.
The paid gas goes as a reward to miners, who actually perform the code execution and distributed data updates. It also serves as a protection against badly designed or malicious code which would run large loops, do a lot of data changes, etc. By focusing on writing your app in such a way that it consumes as little gas as possible, you make it more efficient, trustworthy and reliable.
There's no longer any "server" running "a backend app" that needs to be well secured against tampering. The decentralized consensus of tens of thousands distributed network participants is secure and reliable by design. No one can modify data without the global agreement.
That's why Ethereum is often perceived as such a paradigm-shifting technology. I you need to dig deeper into the internals, check this detailed article: What is Ethereum? A Step-by-Step Beginner's Guide. Since there is a lot of controversy around recent rapid fluctuations of ETH prices, a question arises: how mature and effective is Ethereum? Is it really technically promising? Some of its advocates claim it's "The new Internet", and it's hard to ignore how attractive it became among investors.
The best way to explore this is to build an actual dapp, so let's do this! A dapp consists of two main parts: the contract, running in the Ethereum network, and the client. Here's an example, with mentioned parts colored in purple:.
With that in mind, a contract can be written using the Solidity language and then deployed to the blockchain. Such calls can be done using various client libraries. In our example the client is a web application running in the browser. In order to call Ethereum network API, we need the web3.
Metamask also allows selecting different networks like a local one for testing and Ethereum accounts. There's also Mist Browser - another way to browse and run JS-based dapps, one can also bundle the whole app using Meteor and release it as a standalone package. The client app is just a set of static resources which can be run locally, or be exposed on a web server like Apache. Our showcase application will be a dead simple collaborative scheduling tool, similar to Doodle.
It allows creating a new event with a list of options for voting, as well as casting votes in a secure way. You may be wondering what is the difference between this app and the example Voting dapp from the official Solidity tutorial.
Authorization is done using key string passed through URL. This means that the UX stays as smooth as in case of many other applications where passing a "editor URL" suffices for security. How can this be done when all contract code execution is open and visible? We will use some smart cryptographic functions to achieve this. But let's not jump too far ahead. Here's a list of all the features available in our simplified scheduling app:. As I mentioned, storage is very expensive.
However, there's another interesting feature that we can leverage: publishing events which seems to be many times cheaper. An event can carry some data and it remains stored in the blockchain forever. Then our client app can query all the relevant events and rebuild its internal state. When the events are used as the main source of truth about current state, it's called event sourcing.
In our case, we will apply this concept partially. While writing events is super cheap in terms of gas, reading is a very slow operation, so basing only on events is out of the question.
For the purpose of our example, we will use the events to build a list of all votes with voter names. However, we will also use contract storage to maintain the list of available voting options and current vote counts.
Here's the final architecture:. Additionally, there's Remix IDE which helps to debug the contract when running tests is not enough. Full project sources are available on GitHub. Our exploration begins straight with the smart contract.
In our case it's a single file called DecentralizedSchedule. First, there are some declarations of contract's internal fields and data types:. As we can see, the Proposal type represents a single possible voting option with a name and number of votes already accumulated under this option. The bytes32 type is often used for storing short strings of constant length. Each user here is identified by their address. Connecting to the Ethereum network requires you to have such an address, it's also where your ETH funds for executing dapps are stored.
Finally, we keep a member variable votings , which represents a mapping between a signer and a poll, but this concept of a signer will be discussed a little bit later. Remember that all this data is publicly readable, but can be altered only by calling contract's functions. For the purpose of our showcase app we don't care that the data can be read by anyone, as long as only authorized users can vote. Some public functions of the contract can be marked as constant. This means that they don't modify data and can be executed without paying any gas.
However, gas limit is still checked, which means that an infinite loop will not block, as "hypothetical gas" amount would run out.
Here's one such function:. Executing public function can be performed as a call or transaction. When you call a function, the code will be executed and a return value will be provided, but any state updates or gas expenses will be dismissed right after the function ends. This may be useful for testing contracts or verifying gas cost before transactional calls. If your function is intentionally read-only, you may mark it as constant in order to mark that it should be used only with calls.
Unfortunately Solidity does not support returning structures, this is why we had to go all this way and build arrays, which are then returned in the final "array of arrays" by the voteSummary function. This function is not constant , so it modifies local state. As we can see, the function does some security checks and after that, it stores the user's vote or replaces the existing one.
The last line: VoteSingle msg. The v , r , and s arguments represent digital signature of the caller.
By leveraging hashing algorithms and signatures, we can use the built-in ecrecover function to ensure that function caller is an authenticated client. If you want to explore detailed steps of cryptographic tools used in our example, read the appendix. The fastest way to test your contract is to write some tests with Mocha. First, make sure you are running testrpc.
Then you can call truffle test. Here's a sample test which creates new poll and then calls voteSummary to verify whether returned values match expected initial state:. The frontend part consists of two main views: The "Create Event" view and the "Vote" view. The first one allows defining a poll with possible choices:. When the view is initialized, Metamask injects an instance of web3 which is used to connect to the contract:.
This view simply allows defining event name and a list of options, and then clicking "Create Event". We do this in a child component:. The above code uses the ethereumjs-util library to generate new signer account and call the contract's create function to initialize new poll. Additionally, we use react-router to redirect to a new URL with two parameters:. We can see all voting options with their vote counts. This data is retrieved in the component's constructor, using the voteSummary contract function mentioned before:.
Then, in componentDidMount we start listening to events. Each event will update the component's state, which will cause re-rendering and updating the table with either new votes, or modifications. Even though this is quite slow, we get poll results in the summary, so we can quickly see which option is the winning one.
Finally, pushing the "Vote" button does a transactional contract call:. The cryptoutils call is an internal module which leverages ethereumjs-util to generate a signature of the sender's account id hash using the signer's private key.
See Appendix for details on the cryptography behind this process.
Use Key Management Service (AWS KMS) to securely manage Ethereum accounts: Part 1
Metrics details. As pharmacogenomics data becomes increasingly integral to clinical treatment decisions, appropriate data storage and sharing protocols need to be adopted. One promising option for secure, high-integrity storage and sharing is Ethereum smart contracts. Ethereum is a blockchain platform, and smart contracts are immutable pieces of code running on virtual machines in this platform that can be invoked by a user or another contract in the blockchain network. Here we design a specific smart contract to store and query gene-drug interactions in Ethereum using an index-based, multi-mapping approach. Our contract stores each pharmacogenomics observation, a gene-variant-drug triplet with outcome, in a mapping searchable by a unique identifier, allowing for time and space efficient storage and query.
How to Set Up a Private Ethereum Blockchain in 20 Minutes
The ethers. It was originally designed for use with ethers. Ethers' various Classes and Functions are available to import manually from sub-packages under the ethersproject organization but for most projects, the umbrella package is the easiest way to get started. It is generally better practice for security reasons to copy the ethers library to your own webserver and serve it yourself. The quickest and easiest way to experiment and begin developing on Ethereum is to use MetaMask , which is a browser extension that provides:. A connection to the Ethereum network a Provider Holds your private key and can sign things a Signer. Geth and Parity as well as many third-party web services e. It typically provides:. Once you have a Provider , you have a read-only connection to the blockchain, which you can use to query the current state, fetch historic logs, look up deployed code and so on.
How to Create Private Ethereum Blockchain
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Law and the Blockchain
Cryptographic signatures are a powerful primitive in Ethereum. Signatures can be used to prove to a smart contract that a certain account approved a certain message. Only authorized payments will be allowed, thanks to cryptographic signatures that I will make and send off-chain e. Paying someone with the ReceiverPays contract works a lot like writing a check. The person receiving the payment gets to take money directly out of my bank account, but only if they have a valid check bearing my signature. The ReceiverPays contract holds ether on behalf of its owner and allows that ether to be withdrawn when authorized by a cryptographic signature:.
How to Build a Private Ethereum Blockchain
Home » Guides » Ethereum. Ameer Rosic. If you want to know what is ethereum, how it works, and what it can be used for, without going deep into the technical abyss, this guide is perfect for you. Ethereum is a global, decentralized platform for money and new kinds of applications. On Ethereum, you can write code that controls the money, and build applications accessible anywhere in the world.
Implementing a blockchain from scratch: why, how, and what we learned
How to set up a private ethereum blockchain using open-source tools and a look at some markets and industries where blockchain technologies can add value. In Part I, I spent quite a bit of time exploring cryptocurrency and the mechanism that makes it possible: the blockchain. I covered details on how the blockchain works and why it is so secure and powerful. In this second part, I describe how to set up and configure your very own private ethereum blockchain using open-source tools.
What is blockchain?
RELATED VIDEO: Ethereum private blockchain setupOracles are changing the way we view and create smart contracts. How do we implement them in Ethereum, using nothing but Solidity and standard dev tools? Kosinski explains how to get started and compile a smart contract with oracles. The goal of this, part 1 of the series, is not to get much into the concept of oracle contracts, the philosophy behind them, or even very deeply into what they are; the goal of this part of our Ethereum oracle tutorial is simply to:.
With the advances happening in the area of urbanization, with increased demand for dwellings and an increased number of vehicles on road, finding a parking spot has become one of the major pain points for the citizens. This is mainly due to the limited parking spaces available and difficulty in finding a vacant lot during busy hours. To overcome this limitation, one solution is to create smart parking spaces which are rather easier to find and use. In this work, we propose a Blockchain based solution where parking pools can be created by developing a transparent platform where individuals can rent out their unused land for a stipulated amount of time. A non-fungible token system representing unique parking lots will be created for transparency of the entire system. This also has the added advantage of generating revenue from their otherwise unused property.
Register Now. InfoQ Homepage Articles Private vs. Public Blockchains for Enterprise Business Solutions. Sep 21, 13 min read.
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