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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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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Architecture of an oracle

I am building the architecture of an oracle-based blockchain (ethereum) system. Is it correct to represent the oracle in this way?
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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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interaction between the oracle smart contract and the oracle service [closed]

I want to modify this code to recover the temperature. the oracle smart contract issues a RequestWeather event with the city I need to know the temperature. The oracle node captures the RequestWeather ...
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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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Does Ethereum 2.0 still have use cases for oracles, why?

It seems to me Ethereum 2.0 would only require that one node creates blocks at a time, does that make unnecessary oracles.
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Is first call to oraclize query free in mainnet, as in testnet?

We were trying to include oraclize query to get price feed in one our contracts, as of now we have observed that the first oraclize is free in kovan. Does same applies for mainnet or else we has to ...
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What is a blockchain oracle?

What is a blockchain oracle for smart contracts? And why is it needed? I've seen a lot of posts about "how do oracles work", and "what is the oracle problem" but I don't understand ...
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How can the contract move funds from a user wallet to a contract address

We are creating a system where every month some ethers shall be transferred from user wallet to a contract wallet. We are focusing on creating a dapp too, so a user will initiate this request and once ...
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How is Chainlink decentralized? [closed]

I believe one of the main criticisms of chainlink is that it is not decentralized enough, adding more nodes would be a big step in a positive direction. When I pull data through a node, that node ...
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Explicit type conversion not allowed from “string memory” to “uint256”

I'm using an oracle to get results from a custom api. The result is in string by default. I want to convert it to uint256, so that I can perform basic arithmetic functions. Here's my code: function ...
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How is the volume for the currency pair accounted for on chainlink's reference data feed?

https://feeds.chain.link/ - link for reference. Let's take the LINK/USD feed for example: From my understanding, the aggregation contract fetches the price of LINK in USD from the node operators who ...
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How does chainlink solve the oracle problem? [closed]

I've heard a lot about Chainlink recently -- how Synthetix, Aave and other top Defipulse projects are using them. How exactly does Chainlink solve the oracle problem from a technical perspective?
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Why do I need decentralized oracles?

I've been reading a lot about how smart contracts work, and I'm a little new to the area, but why do we need decentralized oracles? It feels like I can just make an API call from wherever and it's OK?
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How does Oraclize work? [duplicate]

We know that an Oraclize based contract can communicate with the internet sites. We know than Oraclize source is built by Solidity language. We know that there is no command in solidity that can ...
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blockchain oracles to communicate with external api via smart contracts?

Is there is any other oracles other than provable or oraclize to communicate with external api via smart contract.
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Calling a Solidity function automatically in realtime

I have an oracle with a 'getPrice' function that returns the latest ETH/USD price. Let's say, I am implementing a stablecoin contract which requires over-collateralization with ETH. How will I ...
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Provable store an array

I'm trying to understand some basis of Solidity, I get how to get multiple values from one query, but don't really understand how to store them, could anyone explain me how to do it? pragma solidity ^...
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Can't call coinFlip() function the second time

The first time when i run this it runs fine but the second time when i call the coinFlip() function it shows gas estimation failed can someone tell me why it is happening. pragma solidity ^0.6.0; ...
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Chainlink node error: BumpGasUntilSafe FindTxBy Attempt: record not found

I am currently testing sending requests to my Chainlink node on Ropsten. I am following the documentation for running a Chainlink node and all went well until. 40 BumpGasUntilSafe FindTxByAttempt: ...
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Is using oraclize to schedule using execution of a function asynchronous?

I am looking for ways to automatically execute a function call every 24 hours in my smart contract and came across this answer. Is the solution here asynchronous, i.e. can the contract execute other ...
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How to send the RFID card no read using Raspberry Pi to smart contract so the details can be stored on Ethereum blockchain? [closed]

Raspberry Pi reads an RFID card and has to send the RFID number to the smart contract to check further details related to the RFID number. Based on the details the payment is done and stored on the ...
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Orcalize Query not working

function getRandomNumber() public payable { require(msg.value >= 0.000175 ether); // 175,000 gas * 1 Gwei = 0.000175 ETH bytes32 queryId = oraclize_query("URL", "json(https://...
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Chainlink services are not supporting the privateFor transactions in Quorum/Kaleido

We are exploring Kaleido and Chainlink for one of our use cases. What we have done: We have created a network of Quorum/Raft nodes. We had setup the chainlink service for the network. We have setup ...
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Town Crier Relay

I'm reading the paper Town Crier: An Authenticated Data Feed for Smart Contracts and i'm failing to understand this bit The Relay is an ordinary user-space application. It does not benefit from ...
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onlyOwner / onlyProvable with oracle functions using Provable

Is it possible to make a function onyOwner, since one of them must obviously be called by Provable's server? Or is there an equivalent modifier to it, such as onlyProvable? If not, would there be a ...

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