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Ethereum Oracle Explained

Building An Oracle For An Ethereumcontract

Building An Oracle For An Ethereumcontract

Building an Oracle for an Ethereumcontract Smart contracts, by their nature, are able to run algorithmic calculations and store and retrieve data. Because every node runs every calculation, its not practical (and presently impossible) to make arbitrary network requests from an Ethereum contract. Oracles fill this void by watching the blockchain for events and responding to them by publishing the results of a query back to the contract. In this way, contracts can interact with the off-chain world. This introduces obvious trust problems. A decentralized contract that requires trusting a single outside data source is a bit of a contradiction. This can be mitigated by having multiple independent oracles respond to the same queries to form a consensus. For more on Oracles, check out Oraclize , a FinTech company providing a reliable connection between distributed apps. Their explanation of an oracle is a good place to start. The oracle for Tinypay (described in more detail here ) has to do three simple things: Pick up ClientCreated events from the contract Verify DNS records using the data from the event Send a ConfirmClient transaction to the contract once the domain is confirmed I went through a few iterations getting the right implementation, and I want to walk you through them as a tour of development on Ethereum. You can use RPC directly but you probably shouldnt The first time I wrote the oracle, I used Go. I tried to do all of the communication with the Ethereum node using the RPC APIs directly. That was interesting, because I was able to learn a lot about how the Ethereum protocol stores and marshals data at a low level. I had to manually recreate the ABI (Application Binary Interface) in code and use that to both send and decipher messages. The ABI is necessary for Continue reading >>

Oracles, Data Outside Of The Blockchain

Oracles, Data Outside Of The Blockchain

Tutorials and jobs for Ethereum enthusiasts. Smart contracts requirements may need to do actions depending on results of real world events and dont have any native way to communicate with data on the internet.In the context of blockchains, the oracle pattern is the principle of linking real world data that lives outside of the blockchain to actors living inside the blockchain: mainly smart contracts that consumes data in order to decide which action to take. We published an article that present the basics of what is an oracle and how to implement one for the Ethereum blockchain. In this article youll see different uses cases and where to use an Oracle. We also cover a simple oracle implementation in Solidity that mimic a basic insurance contract on the blockchain. As Oracle can take many forms, our second article explains how to use the Oraclize platform to fetch data from the internet and use it in your smart contract . Our example shows how to fetch the current USD price of Ethereum from a web API. Continue reading >>

How To Learn Solidity: The Ultimate Ethereum Coding Guide

How To Learn Solidity: The Ultimate Ethereum Coding Guide

How To Learn Solidity: The Ultimate Ethereum Coding Guide Angel Investors, Startups & Blockchain developers... This Guide will walk you step -by-step in learning Solidity. The Ethereum Foundation has been shaking up the world of blockchain since the early days of the project, around late 2013 and early 2014. Ethereum really kickstarted the Bitcoin 2.0 and what we think of as the blockchain movement, after the first big Bitcoin bubble up past $1000 USD on the markets got everyones attention. Ethereum is a blockchain project with a cryptocurrency, Ether, similar to Bitcoin, but Ethereum has the added feature of a (nearly) Turing- complete virtual machine language and processing capability embedded into the node implementation. The Ethereum Virtual Machine (EVM) allows Ethereum nodes to actually store and process data in exchange for payment, responding to real-world events and allowing a lot of new opportunities to support on-chain applications that were never before available to developers and real-world users. I had the luck to actually be in Switzerland in early 2014, and to get to visit an Ethereum holon and hang out with some of the Ethereum founders before the Ether token sale, back when they were self-funded. I asked Mihai Alisie what an Ethereum smart contract is, and he explained: Smart-contracts are a way for people all across the globe to do business with each other even if they dont speak the same language or use the same currency. So thats really the perspective I begin with, the idea that we can define programmatically the rules of a business contract, in a simple machine language, to bring people together and allow them to conduct business in a trustable, secure, and automated fashion. Solidity Language itself is a tool that we use to generate machine-leve Continue reading >>

Why Many Smart Contract Use Cases Are Simply Impossible - Coindesk

Why Many Smart Contract Use Cases Are Simply Impossible - Coindesk

Why Many Smart Contract Use Cases Are Simply Impossible Dr Gideon Greenspan is the founder and CEO of Coin Sciences, the company behind the MultiChain platform for private blockchains. In this opinion piece, Greenspan discusses blockchain-enabled smart contracts and why this application of the technology may be suffering from inflated expectations. As the developer of a popular blockchain platform, Isometimes gets asked whether Ethereum-like smart contracts are on the MultiChain roadmap. The answer I always give is always: 'No, or at least not yet'. But in the hype-filled world of blockchains, smart contracts are all the rage, so why ever not? Well, the problem is, while we now know of three strong use cases for permissioned bitcoin-style blockchains (provenance, company recordkeeping and lightweight finance), we've yet to find the equivalent for Ethereum smart contracts. It's not that people don't understand what they want smart contracts to do. Rather, it's that so many of these ideas are simply impossible. When smart people hear the term "smart contracts", their imaginations tend to run wild. They conjure up dreams of autonomous intelligent software, going off into the world, taking data along for the ride.Unfortunately, the reality of smart contracts is more mundane. A smart contract is a piece of code that isstored on an blockchain, triggered by blockchain transactions and which reads and writes data in that blockchain's database.That's it. Really. A smart contract is just a fancy name for code that runs on a blockchain, and interacts with that blockchain's state. And what is the code? It's Pascal, it's Python, it's PHP. It's Java, it's Fortran, it's C++. If we're talking databases, it's stored procedures written in an extension of SQL. All of these languages are Continue reading >>

Blockchain Oracles Ternity Blog

Blockchain Oracles Ternity Blog

Oracles are essential for the realization of the blockchain-based sharing economy. Yet, they are one of the least discussed components of blockchain systems. Here is our tribute to oracles, smart-contracts little helpers. Oracles, in the blockchain sense of the word, are an important part of the technological stack required for a wide variety of decentralized applications. They are a link between the physical universe and the virtual reality of blockchain platforms and an essential part of the promise of smart-contracts. At the same time, oracles implementations do not get the required attention in a global community primarily focused on blockchain platforms and decentralized applications. There is still confusion about: Perhaps part of the general confusion is created by the name itself oracles. When talking about oracles in the blockchain ecosystem, we are not referring to this: What we are in fact talking about are tools that allow blockchains to learn the outcome of an event. As such they make statements about something that happened in the past. Oracles do not make predictions about the future. Oraclesreport. A prediction market (PM) used to accumulate information about a future event can act as an oracle. In this case the PM can be used as a source of information about what the oracle can potentially report. For example, the PM can inform if the oracles more likely report is Yes (as opposed to No). However, the oracle will always only report on a fact, in this case the prediction markets final outcome. Access to feeds of information originating in the physical world is absolutely essential for the development of the decentralized economy. All the applications running on a public blockchain require triggers in order to provide a service, usually in the form of an Continue reading >>

Github - Dehydr8/oracle-service: An Example Oracle Service For Ethereum

Github - Dehydr8/oracle-service: An Example Oracle Service For Ethereum

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. An example of an Oracle Service mechanism for the Ethereum network An Oracle Service can be defined as a data carrier for decentralized apps (definition from oraclize.it ) As Smart Contracts cannot fetch data from the outside world on their own, Oracle Services come into play and do it for them. This project is meant to describe the approach a developer would take in implementing their own Oracle Service for the Ethereum Network. Emit HTTP request descriptors RD (and the requesting contract address CA) as Ethereum events Listen for these events using a filter with a separate program (on a physical machine) Perform the HTTP request RD and send the result back to CA by calling an agreed-upon function (__callback in our case) Smart Contracts in the contracts directory PSOraclize.sol - responsible for emitting/logging the user request PSOraclizeAPI.sol - API describing the usingPSOraclize contract TestContract.sol - An example contract using our Oracle Service Java (Maven) project - The service that actually makes the HTTP requests The Java project can be compiled by running (given that you have maven installed and it is on your PATH) The Solidity contracts can be compiled using your favorite Solidity compiler and should be deployed to the Ethereum network. Note that the TestContract requires the deployed address of the PSOraclize contract in its constructor. I personally use Truffle for managing and deploying the contracts. The following deployment script comes in handy when deploying contracts that depend on another contract Continue reading >>

Building Your First Ethereumoracle

Building Your First Ethereumoracle

Blockchains are inherently self-sufficient. The entire deterministic model of a traditional blockchain is hinged on the fact that during transaction execution (which updates the state of the system) blockchains cannot perform any logic which is derived from sources external to the blockchain. All external data to the overall system must have, at some point, come from the input to a transaction, which has been recorded into a block. On the Ethereum blockchain, for example, developers are allowed to deploy smart contracts that perform logic given some inputs. The executing logic in a smart contract cannot do anything outside of the blockchain. It cannot reach out and hit a web service from the internet. The only way to get data into a smart contract is to pass it in with the transaction. The only way to update blockchain state is to trigger that state change by sending a new transaction into the system. Consider what would happen if a smart contract were allowed to hit an API endpoint to retrieve some data that was used in the smart contracts execution. If the contract were deployed today into a new block, the API endpoint might return But then tomorrow, the API operator changes the endpoint response to return A month from now someone is newly syncing the Ethereum blockchain, the block containing our smart contract is executed, and the API returns a different response than what it returned a month ago. The state of the newly synced blockchain will be different than the state of a blockchain that existed last month. This is no longer a fully self-deterministic blockchain. My blockchain looks different than your blockchain after the same sync, with the same blocks. Said another way: given the full set of blocks, a node must be able to recreate the final state of the blockc Continue reading >>

Oracles In Ethereum - A Simple Guide

Oracles In Ethereum - A Simple Guide

Motivation: Ive been trying to find a tutorial on building an Oracle in Ethereum, only problem is that the articles online are either out of date (pre web3 v1.0.x) or the source code provided is structured in such a way that makes it incredibly tough to follow (having python, c# and javascript in one project with no clear description of what each language is doing and why its necessary). This guide assumes you have a basic understanding of the solidity language Goal: By the end of this guide, I hope to have helped you build and deploy your Oracle onto your own private testnet >>> Click here for the boilerplate project <<< An Oracle is, simply put, a smart contract that is able to interact with the outside world, in the world of Ethereum that is known as off-chain. I put smart contracts in quotations because some people argue that Oracles arent exactly a real smart contract. Example: Say youre writing a smart contract that needs to retrieve weather data, however your contract cant make arbitrary network requests on-chain. You need something that trustable (all user input arent) and is able to listen and respond to specific events on the blockchain. The solution: Oracles. This guide will be building a simple Oracle that retrieves bitcoins total market cap from coinmarketcap and store it into the blockchain. { "total_market_cap_usd": 198558465250.0, // This is that we want to store "total_24h_volume_usd": 4974818568.0, "bitcoin_percentage_of_market_cap": 61.65, "active_currencies": 896, "active_assets": 360, "active_markets": 6442} Ill be using the truffle framework and testrpc for this guide. You can install them by running: npm install -g truffle ethereumjs-testrpc Im using truffle because is has some really nice abstractions that allows me to interact with web3 (almost Continue reading >>

Blockchain Oracles, Explained

Blockchain Oracles, Explained

Ethereum has made possible the creation of DApps - decentralized applications that operate entirely on a Blockchain. These apps can offer some great advantages, but communication with the outside world might not be as easy without oracles. Ethereum has made possible the creation of DApps - decentralized applications that operate entirely on a Blockchain. These apps can offer some great advantages, but communication with the outside world might not be as easy without oracles. Blockchain,DApps,Smart Contracts,Applications,Decentralization,IBM,Microsoft,Communications Blockchain oracles sound like something from ancient Greek mythology, and in a way, they function in a similar role. In ancient stories, people didnt have enough information to make decisions and turned to oracles for information beyond their understanding. In the same way, Blockchains like those of Bitcoin and Ethereum, do not have ready access to information outside of the chain, and so there is no direct way to validate the conditions that smart contracts are based on. An oracle is, simply put, a translator for information provided by an outside platform. Oracles provide the necessary data to trigger smart contracts to execute when the original terms of the contract are met. These conditions could be anything associated with the smart contract - temperature, payment completion, price changes, etc. These oracles are the only way for smart contracts to interact with data outside of the Blockchain environment. Oracles are radically important. Just like the ancient stories could never have occurred without proper external information, smart contracts cannot function without some data source. Without access to these sources of information, use cases for smart contracts drop to just a tiny fraction of their pot Continue reading >>

What Is Chainlink? A Beginners Guide To Decentralized Oracles

What Is Chainlink? A Beginners Guide To Decentralized Oracles

ChainLink is a decentralized oracle service, the first of its kind. When Ethereum went live in 2015, it revolutionized what blockchain could bring to enterprise solution and traditional business. Blockchain was no longer just a medium for new age financial transaction, confined to Bitcoins potential to disrupt traditional currency exchange. With Ethereum powered smart contracts, Vitalik Buterin opened up a Pandoras Box of use cases for blockchain technology. Problem is, per their design, smart contracts can only manage data on the blockchain. Their potential, the ability to provide tamperproof, decentralized applications for uses the world over, is still largely untapped, as many of the smart contract programs built on Ethereum lack a bridge to the real world industries theyre trying to improve. This is where ChainLink comes in. With ChainLink, smart contract users can use the networks oracles to retrieve data from off-chain application program interfaces (APIs), data pools, and other resources and integrate them into the blockchain. Basically, ChainLink takes information that is external to blockchain applications and puts it on-chain. For many of the blockchain protocols out there, oracles like ChainLink will be necessary to access the data that these protocols need to operate. As such, ChainLink is, as it names suggest, the link that connects blockchain to existing infrastructure. If thats enough to sate your appetite, you can skip ahead to our info on markets, wallets, and the like. But if you want a more thorough and technical explanation of ChainLink, lets jump down to the next section. ChainLinks core objective is to bridge on-chain and off-chain ecosystems, and as such, it has two main architectural components: on-chain infrastructure and off-chain infrastructu Continue reading >>

What's A Blockchain Oracle? Information Oracles & External Data Feeds

What's A Blockchain Oracle? Information Oracles & External Data Feeds

There are different types of oracles based on the type of use. We differentiate between software oracles, hardware oracles, consensus oracles and inbound and outbound oracles. Software oracles handle information available online. An example could be the temperature, prices of commodities and goods, flight or train delays, etc. The data originates from online sources, like company websites. The software oracle extracts the needed information and pushes it into the smart contract. Some smart contracts need information directly from the physical world, for example, a car crossing a barrier where movement sensors must detect the vehicle and send the data to a smart contract. Another use case is RFID sensors in the supply chain industry. The biggest challenge for hardware oracles is the ability to report readings without sacrificing data security. Oracalize proposes a two-step solution to the risks, by providing cryptographic evidence of the sensors readings and anti-tampering mechanisms rendering the device inoperable in the case of a breach. These provide the smart contract with data from the external world. Example use case will be an automatic buy order if the USD hits a certain price. These provide smart contracts with the ability to send data to the outside world. An example would be a smart lock in the physical world which receives a payment on its blockchain address and needs to unlock automatically. Prediction markets like Augur and Gnosis rely heavily on oracles to confirm future outcomes. Using only one source of information could be risky and unreliable. To avoid market manipulation prediction markets implement a rating system for oracles. For further security, a combination of different oracles may be used, where for example 3 out of 5 oracles could determine t Continue reading >>

How Do Oracle Services Work Under The Hood

How Do Oracle Services Work Under The Hood

How do oracle services work under the hood I have read many questions about oracle services, but I do not understand how they work.Often I read answers like this: Smart contract can not access an external environment... But how do "Oraclize" or "RealityKeys" work, and how can I build My own oracle service on a public blockchain? Basically what needs to happen is that somebody says what data they want, the trusted service provides an ID that identifies it (in our case a hash of the data) and a key they'll sign the result with, and somebody sends a transaction to the contract. Then we wait for the result. Once the result is known, the trusted service signs it with their key, somebody sends another transaction containing the signed data to the contract, and the contract does whatever is supposed to happen. This can be done either on-chain or off-chain. We do this off-chain, so we just provide signed data and a key, and users grab this data off our site and send it to their contracts themselves. This would normally be part of a DApp, so for example PredictionToken have a screen that creates a transaction to grab the ID from our site and sets up a contract, and another screen to grab the signed data from our site and send a transaction to settle the contract. Oraclize do it on-chain, so your contract sends a request to their contract, and their contract writes an event to the event log and returns an identifier. They have a process watching the event log, and when the data is ready they send it as a signed transaction to your contract, which checks the sender of the contract (this is another way of checking who signed the data) and does whatever it's supposed to do. From a developer's point of view the advantage of doing it on-chain is that you only have to deal with reques Continue reading >>

Ethereum And Oracles

Ethereum And Oracles

One of the more popular proposals for implementing smart contracts differently from the way they are typically presented in Ethereum is through the concept of oracles. Essentially, instead of a long-running contract being run directly on the blockchain, all funds that are intended to go into the contract would instead go into an M-of-N multisig address controlled by a set of specialized entities called oracles, and the contract code would be simultaneously sent to all of these entities. Every time someone wants to send a message to the contract, they would send the message to the oracles. The oracles would run the code, and if the code execution leads to a withdrawal from the contract to some particular address then the oracles circulate a transaction sending the funds and sign it. The approach is still low-trust, as no single oracle has the ability to unilaterally withdraw the funds, but it has a number of particular advantages: Not every node in the blockchain needs to perform the computation only a small number of oracles do It theoretically does not require as a platform anything more complicated than Bitcoin or Ripple as they currently stand Contracts have a somewhat higher degree of privacy although exit transactions are still all visible, internal computations may not be. The scheme can also be augmented with secure multiparty computation protocols so the contract can even contain private information (something that would take efficient and secure obfuscation to work directly on Ethereum) Contracts can rely on external information (eg. currency prices, weather) since it is much easier for N nodes to come to consensus on the result of an HTTP request than an entire blockchain. In fact, they can even rely on data from proprietary APIs, if the oracles subscribe to Continue reading >>

How Oracles Connect Smart Contracts To The Realworld

How Oracles Connect Smart Contracts To The Realworld

How Oracles connect Smart Contracts to the realworld Ethereum-based Smart Contracts are simple but effective forms of code designed to provide services or goods in exchange for certain values (be they monetary or time-based) being fulfilled. However, as they are wholly-based upon the Ethereum network, the input of information must be limited in order to not overwhelm the lightweight nature of the Blockchain. In essence, the Smart Contract is a judge, yet it needs a solid and reliable source of information to make correct judgements. This is where Oracles come in. Oracles are trusted data feeds that send information into the Smart Contract, removing the need for Smart Contracts to directly access information outside their network, thus lightening their workload. Oracles are usually supplied by third parties and are authorized by the companies that use them. Of course, critics will highlight the irony of using third parties to solve an issue on a decentralized platform that boasts of reducing the need for such intermediaries. But Oracles are a necessary step forward in the practical utilization of Smart Contracts. The utilization of real world data in Smart Contracts requires reliable Oracles. This all sounds quite easy on the surface, but in fact the issue of transferring information through Oracles is a subject of much debate among Smart Contract users and developers. In many businesses cases such as simple service retail or travel services, Oracles handle their task quite well, supplying basic yet crucial information to Smart Contracts that can then decide what to do afterwards. Imagine, for instance, a Smart Contract being fed information by a trusted banks API and the delivering the said amount to the user. Pretty simple, right? But In the case of more complex tasks Continue reading >>

Proof-of-work Oracle

Proof-of-work Oracle

Would love your thoughts on my idea, a proof-of-work oracle. Basicatlly it works as an oracle schema that implements a mineable proof of work (POW) competition to eliminate reliance on trusted third parties for access to off chain data. Users engage in a POW competition to find a nonce which satisfies the requirement of the challenge. The users who find a nonce which correctly solves the POW puzzle input data for the POW Oracle contract and receive native tokens in exchange for their work. The oracle data submissions are stored in the smart contract for use by other on-chain operations To give an even simpler explanation, think mineable token, but with each solution submission, you get to put in some data (say BTC/USD price). The first n solutions are accepted and then the median is rewarded (neighboring answers get uncle rewards) in the form of a newly minted POW oracle (POWO) tokens. The median value is then timestamped and placed into a time series array which can be accessed through a getter function which charges parties a small amount of POWO tokens. It propose to use a schelling coin like oracle but which could be appealed to the miners in last ressort: Thanks for the reply, this is a great system but in my mind its a different problem since its not on Ethereum. Since its not on Ethereum, you actually need an Oracle to get Truthcoin data into your smart contractshence you need a centralized Oracle system to get decentralized info. Augur and Gnosis have something similar on chain, but its more of the POS version of getting to the truth whereas I like to think of our solution as the PoW route. I dont propose using truthcoin, but too look at their design and explanations which may be usefull for in your PoW Oracle design. However I dont see why we would want to was Continue reading >>

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