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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Smart contract and hardware oracle

i wrote a smart contract using solidity to read , store and compare temperature from external sensor with a preset value. in this case i need oracle to authenticate the external sensor readings. so ...
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On writing a smart contract to store temperature measurements [closed]

i wrote a smart contract using solidity to read , store and compare temperature from external sensor. what is the best hardware oracle to link it to this smart contract?
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How to validate the Chainlink price feed at a specific time

Suppose that in my solidity contract, I need to see the price of ETH in terms of USD at a specific time, say on January 1, 2021. I would like to use the Historical Price Data Feed from chainlink (URL ...
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Is there a mechanism for fair, trustless Chainlink oracle pricing?

When using a Chainlink oracle node that you don't have a formal commercial agreement with, the user pays the node operator in Link tokens, but the node operator bears the cost of transacting on the ...
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Is there a time oracle for a Solidity calendar library?

According to the solidity documentation: Take care if you perform calendar calculations using these units, because not every year equals 365 days and not even every day has 24 hours because of leap ...
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How to return a Chainlink API Call to another contract?

I need to call a function that returns the uint value requested by the oracle from another contract function. I am trying the next... but I think I am going by the bad way. Any solution for that? The ...
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How are DeFi projects able to pay for data provided by Chainlink oracles?

How are DeFi projects and dApps able to pay for used oracles/api calls? If we assume the needed product has to be updated with a feed every minute and a call would cost 0.1 LINK it would cost 144 LINK ...
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Why is this particular line of code stopping the smart contract from being deployed?

I am coding a smart contract which will be integrating ChainLink's decentralized oracles, however I've run into an issue that is preventing me from deploying the smart contract on Remix IDE. The ...
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How to build a decentralized bridge between two blockchains?

I am trying to build my own custom bridge between Ethereum and Binance Smart Chain so that people can transfer tokens and possibly some other assets from one chain to another and vice versa. For this ...
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What is the best way for a smart contract to constantly listen to a price feed and execute immediately once the price is reached?

I have compiled a smart contract that is supposed to take bets from 2 addresses, a bet creator and a bet taker. The bet is on the price of ETH/USD (via ChainLink). What would be the best way to for ...
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Coding a smart contract for people to easily start a trustless bet online. How to improve my smart contract?

so I really want to create a smart contract for the community to use - one where two people can easily and trustlessly make a bet between each other. V1 of the smart contract would be where two people ...
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How to detect false data feed from Chainlink oracles

I understand Chainlink uses explicit and implicit staking to enforce honest behavior. However, what is the mechanism used to catch the misbehavior of oracles (i.e., reporting wrong data)?
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Making GET request with ChainLink (using dynamic URL Params)

Im quite new to using ChainLinks Client to make requests to external API's. I am generating random numbers using their VRFBaseConsumer in my Wallet Contract. Upon receiving a newly generated number, ...
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ChainlinkClient.sol v0.8.0 NOT working (request.add(“get”, “<url>”))

Im am relatively new to using ChainLinks ORACLE contract in solidity. I have recently managed to successfully integrate their VRFConsumerBase.sol in my consumer contract to generate random numbers. ...
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How to convert TRX to USD in solidity?

I need to convert TRX to USD in solidity for a project. Earlier I used Chainlink's AggregatorV3Interface for BNB to USD. But there is no resource for TRX there. Any help would be appreciated.
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Uniswap V2 Swap Fee

On my calculation with formula X * Y = K and Swap Fee 0.3%, My Result Value of Input or Output Token Amount is nearly same as UniSwap V2 User Interface Estimated Amount. But Sometimes, My result is ...
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I am trying to use chainlink using remix and i followed the chainlink docs

I am facing this issue,What to do now? My Code pragma solidity ^0.6.7; import "https://github.com/smartcontractkit/chainlink/blob/master/evm-contracts/src/v0.6/interfaces/AggregatorV3Interface....
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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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