Questions tagged [oracles]

Oracle is a way of implementing a Smart Contract. Instead of running the contract code directly on the blockchain, the code is executed on some special off-chain entities called oracles which then send the result of the code to the blockchain network with a signature.

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Prediction Market (result publishing issue)

I am trying to create e prediction market where people can contribute in predicting (which side is going to win?) by spending Ether, but unfortunately i am getting error ("Error: invalid ...
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An oracle for real currency values

I would like to get an oracle for values of countries' based currencies. Are there such free oracles?
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JIT events on etherum

I would like to write a contract, that fetches a data from oracle in a specific point of time (or later) Is there any option to pop up an event in some point in the future in Ethereum contract? The ...
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How can I protect my Chainlink oracle fulfill method?

Background: I'm writing a contract that inherits ChainlinkClient in order to make an API request via an oracle job: function fetch() private returns (bytes32 requestId) { Chainlink.Request memory ...
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What is best approach for generating random NFTs?

I am thinking of developing small DApp where user would collect cards (NFT). Each card would have some image and value associated with it. User collects cards by purchasing Pack of Five Cards which ...
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Price feed of multiple coins in a single GET request

I have used Chainlink oracle to get the price feed of a single coin. But I want to fetch the latest price of 100s of coins from the smart contract using oracle. Is it possible to get the price of ...
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Chainlink Price Feed - function fails when price not hard-coded but correctly displays in console

I'm experiencing a challenge and hoping for some guidance/help/assist... I've been working on implementing price feed. Testing locally with hardcoded return price works like a charm, no issues. When ...
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Can a chain link node listen to ethereum smart contracts events?

Can a chain link node listen to ethereum smart contracts events? Let’s say I want to provide data to a node from a smart contract. Can a I link a chain link node and use a smart contract as an oracle?
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Fetch price data: on-chain oracle vs smart contract function

I want to get the latest and most accurate price data from Uniswap and found out that I can either call the getAmountsOut() function which gives me the amount of tokens I will get in return of a given ...
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Make a GET Request over the Binance Smart Chain with a Chainlink Oracle

I am trying to call to an BSC Oracle to make an HTTP request according this ChainLink example. In my example I am goin to use the BSC mainnet 56 and a other JobID obviously: My steps: I created the ...
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Can I use chainlink on a private blockchain?

Can I use chainlink on a private blockchain built with Geth? I found that the online tutorials are basically about how to use chainlink on the Kovan test chain. I want to know whether chainlink can be ...
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How does the oracle judge whether the request has been attacked by a man in the middle

The oracle machine can initiate a request to the data source whose URL is the HTTP link address. How does the oracle machine determine whether the HTTP request has been attacked by a man-in-the-middle,...
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EthTx adapter won't respond in Chainlink job, fails with “transaction reverted on-chain”

We're using the standard truffle box (https://github.com/smartcontractkit/box) to deploy Chainlink contract ($LINK definition, Oracle, sample end-user contract, etc) on a private Ethereum testnet. ...
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Is Oraclize / Provable Things dying? [closed]

I'm doing some research on how to generate truly random numbers on the blockchain. Aside from Chainlink VRF, the other viable solution seems to be Provable Things (former Oraclize) with their random ...
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Smart Contracts and API Calls: How to check API repeatedly without paying a fee?

I'm new to this entire space, so please bear with me. I'm trying to create a betting app. I want people to sign the contract and say they'll put up some money that they'll either win or lose depending ...
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Json RPC eth_sendTransaction data parameter

I have a question concerning the data parameter of the json RPC method eth_sendTransaction. Is it possible to send any kind of data structure with this method to a smart contract? Is it possible to ...
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Chainlink - on-chain contract functioning

The on-chain aggregation smart contract for ETH/USD on the mainnet (https://data.chain.link/eth-usd) is at this address https://etherscan.io/address/0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419#code. If ...
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Send ETH Transaction based on price

I'd like to be able to execute an ETH transaction on chain based on a change in price of an asset. This seems like a job for an Oracle, but aside from an app that's not on chain that watches for ...
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Security implementation of a function in Solidity

I'm here for asking some tips on calling function from other contracts in solidity. Here is the function for generating a random number (which I need in the main contract) using the chainlink VRF. ...
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How I can check request status with provable.xyz?

Simple question but I failed to find the answer. Before Oraclize became provable, there was an api endpoint for checking the status of a specific request id. This for example helped to determine if an ...
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Oraclize external rest api call failure handling

Using https://oraclize.it, I can perform something like this oraclize_query("URL","json(https://api.postcodes.io/postcodes).status", '{"postcodes" : ["...
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How can oracle PROVE that a transaction was mined?

I want to build an oracle similar to OmniBridge for xDai or Arbitrary Message Bridge but I am worried about how to make it secure. It would seem such an oracle should be reliable, as long as there is ...
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Oracle service and oracle smart contract

I read this article https://medium.com/@robinagist/building-an-ethereum-oracle-with-web3-js-1-0-1272b59cfc31 but there are some things I didn't understand. Does the oracle need a node (like geth or ...
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What is the largest number that can be returned from a Chainlink Price Feed?

Is it safe to assume that chainlink oracles have an upper bound on the price feed, eg it fits into uint96, or perhaps a smaller or larger number? It would be great to know the absolute largest number ...
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Is an Oracle a Smart Contract or an EOA?

As provided in the Title, I am not clear about the concept connected to Oracles. I'm wondering if it is a Smart Contract or an EOA? Can somebody bring more clarity to the concept?
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Do all Chainlink feeds return prices with 8 decimals of precision?

It looks like many Chainlink feed aggregators have 8 decimals of precision: ETH/USD, which returns 140330173736 = $1,403.30173736 BTC/USD, which returns 3696759888474 = $36,967.59888474 I found the ...
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Why is serprent considered untrusted?

Serpent was way to fetch Diesel prices from the oraclize api at fixed intervals. On GitHub, it s written audits proved the code to be flawed, but where are such audits? I m meaning why is it flawed?
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What is the oracle component?

I'm trying to build my own oracle for a project (so I don't use chainlink or oraclize) and I've read this https://medium.com/@robinagist/building-an-ethereum-oracle-with-web3-js-1-0-1272b59cfc31. In ...
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Chainlink Price feed Main contract points to Kovan. Why? [closed]

I'm setting up price feeds with Chainlink. https://docs.chain.link/docs/ethereum-addresses#mainnet This page has sections: Mainnet, Rinkeby, Kovan. Under Mainnet.. Clicking a pricefeed takes me to .. ...
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How to make sure that GET call is coming from Oracle and not some other entity?

EDIT: I need to edit the question since people did not understand what is it that I want to accomplish. Please consider this scenario: User uses a DAPP and initiates some smart-contract function, ...
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ChainLink oracles - are they free to use? Is there an oracle alternative onchain?

How does it work, exactly? We just call this on-chain to get the latest price... but would our contract have to transfer some LINK to it, or what? https://docs.chain.link/docs/get-the-latest-price ...
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Pegging a contracts 'price' to USD?

I have a contract / dapp that is "pay to play". You send X amount of Eth, and you can play. I have a price feed working via Chainlink, but I'd like to peg the Eth amount to USD. Where the ...
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What is the verification process of nodes on chainLink?

chainLink is a decentralized system similar to Ethereum, which can help smart contracts execute get requests and return the results. The result of chainLink execution also needs to be verified by ...
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How chainlink guarantees the authenticity and accuracy of the data it returns to the smart contract

Given that the oracle and the "request/response" mechanism may be operated by multiple entities, the possibility of data being tampered with during transmission obviously exists. I want to ...
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Getting data from outside source during a transaction once per day

Is it possible for a token contract to call an oracle to fetch data once every so many hours? Let's say the token was going to use a random number for some decision it was going to make in its ...
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Do miners or validators have to pay LINK fees for oracle service?

I will try to ask a question based on the use case. Assume I only use 1 oracle (ignoring the fact decentralization of chainlink oracles) to execute GET call to an API which returns bool information (...
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What is the cost of using a Chainlink Oracle?

I use the market.link to check available jobs and each job has its own price in terms of link. My question is how many times this fee will be paid? For example: Let's say the API GET request costs 0....
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How to pass argument to Chainlink selector?

I have a mapping with integer keys and struct values. mapping (int => Client) public customers; Each customer has its own proof argument which I am trying to update with a Chainlink API call. Here ...
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How do oracle services interact with logs?

I am approaching blockchain and smart contracts for the first time and I have trouble understanding some concepts. I read this article https://medium.com/decentlabs/building-your-first-ethereum-oracle-...
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Using Chainlink External Adapters doesn't return anything

Trying to use this Bitcoin Adapter But having some issues specifically with the copyPath argument and the callback arguments. For one, I would like to retrieve multiple parts of the JSON that is ...
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Retrieve Uniswap tx data in my solidity smart contract

As the title says, I have my Solidity smart contract and I am trying to import in ti some public data from the Uniswap contract. In particular I would like to have the tx data stored in my contract (...
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Chainlink node not connecting to External Adapter

I'm trying to use the Chainlink External Adapter to connect my contract to Twitter but my node I'm running is seemingly not able to connect to the adapter at localhost:8080 even though the adapter ...
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Does Chainlink store Oracle response for a transaction somewhere on blockchain?

Lets consider an example of transaction lifecycle where a smart contract uses Oracle to get external data ETH/USD price feed that is changed in real-time. Transaction is executed during mining, so it ...
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Are oracles too slow for DEFI arbitrage?

It seems that a lot of platforms that make you money via 'arbitrage' rely on Oracles to find a profitable spread opportunity. I assume users are competing against other users (on the same platform) ...
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Unable to get response back from chainlink node using truffle console

I am trying to fetch close prices of a property deployed on a server running on a chainlink node. Here's what a snippet from my contract (RealEstateAPIConsumer.sol) looks like : function ...
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Could there be multiple asset pools In a DAMM liquidity pool?

In a DAMM (dynamic automated market making) DEX (decentralized exchange) the ration between two assets, e.g. DAI/ETH does not have to be 50/50 anymore, like it used to be in a AMM, (automated market ...
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Is Chainlink's price reference data free to consume?

I was looking at feeds.chain.link and it's not immediately obvious if anyone can tap into all these price feeds without incurring a cost: For instance, I did find the ETH/USD aggregator contract, ...
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Rationale for using ETH as the unit of account for oracle pricing data

These are Compound Finance's former oracle contracts: PriceOracle PriceOracleProxy I say "former" because Compound switched to the Open Price Feed UniwapAnchoredView.sol oracle on Aug 17, ...
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Should I use an average or median price for my oracle?

Excerpt from Compound's The Open Price Feed: This is accomplished through a View Contract, which reads, parses, aggregates, transforms, etc from the storage contract. The determination of ...
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Rock, paper, scissors and Secrether.io

I have thought of a RPS game using secrether.io: playerA hashes keccak256(move+11charsRandomData) as hash and sends it to RPS smart contract. RPS creates a transaction to Secrether Smart Contract - ...

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