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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177 views

Verifying the authenticity of a customer

One of the strengths of blockchain, and specificallly, Ethereum, is the ability to have a complete record of customer orders from customer setup (for new customers) to customer delivery of goods. I ...
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1answer
490 views

Regarding Oraclize call in smart contract

I have two functions which uses Oraclize call.I have to call these functions one after other / or simultaneously. Sample code for your reference :- pragma solidity ^0.4.0; import "./usingOraclize....
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1answer
491 views

Return uint value from storage contract

When I store data in the oracle and then try and refer to it on the testrpc through the pay function it just doesn't work. Any ideas? pragma solidity ^0.4.6; contract Oracle{ struct ...
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0answers
927 views

How to create an Ethereum side-chain aka pegged chain? [closed]

With the ETH at an all time high and the gas price still at 20G Wei Ethereum transactions are becoming uneconomical. We want to create an accounting system based on smart contracts which would simply ...
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2answers
338 views

Smart contract update every 60 seconds with Oraclize

I am trying to create a smart contract using geth and ethereum-bridge (Oraclize) on a private network. I want to know the number of visits to a youtube video. The first time it works correctly but I ...
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1answer
648 views

Implementation of Oraclize callback tests with Truffle/Mocha

I'm trying to write tests in Mocha/JS with Truffle for a Solidity function that uses Oraclize. I want to test if the result in the callback of my Oraclize query is correct. As Oraclize needs some time ...
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1answer
371 views

How do I calculate the gas limit for an oraclize query?

I have an oraclize query in my solidity contract and if I don't up the gas limit it doesnt work. My oracalize queries have call backs which call more oraclize queries.
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400 views

Avoiding out of gas errors when making Oraclize queries that have callbacks which trigger more queries

I have a contract that I want to automatically check the price of ethereum everyday. right now I have a method called startContract which calls a function setConversion which makes a query set for 1 ...
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1answer
319 views

What are the differences between callback and OAR address

I am using Oraclize with testrpc and truffle and I have confused in some points Now when I choose an address account when run the bridge, why and what is the purpose of the choice. node bridge -a 1 ...
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1answer
217 views

Question regarding Testrpc evm_increaseTime and oraclise

After creating my contract at t1, which is supposed to be called back from oraclise using Ethereum-bridge at t2. I did a time jump to t2 on testrpc using evm_increaseTime and evm_mine. Yet the ...
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0answers
264 views

How can I automatically send token in exchange for Ether

I want to send tokens in exchange for Ether. And I want to send tokens in terms of 1 JPY / 1 token. So I have to get ETH/JPY rate on smartcontract. I tried to use oraclize to get its rate. But because ...
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1answer
1k views

How to access Swarm content from ethereum smart contract using oraclize

I am trying to access the content in a file that I uploaded to Swarm using oraclize. I found a smart contract in https://github.com/oraclize/ethereum-examples/blob/master/solidity/Swarm.sol I was ...
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0answers
79 views

Truffle test + Oraclize. Invalid Jump on the second call [duplicate]

I'm currently developping an Ethereum dApp using Truffle, Test-RPC, Oraclize and ethereum-bridge. So at the moment everything is local. My issue: I notice that when I run more than one test calling ...
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1answer
528 views

Error in dapp developed using 'Truffle' framework - Issue in fetching the result from Oraclize-Query

I am developing a dapp using 'testrpc' and 'truffle'-3.1.1.I have also used ethereum-bridge for Oraclize.I have written a smart contract function which calls a url using 'OraclizeQuery'. The ...
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1answer
500 views

Oraclize_ Error: The contract code couldn't be stored, please check your gas amount

When i am going to deploy this code its give error:The contract code couldn't be stored, please check your gas amount. Solidity CODE: pragma solidity ^0.4.0; import "github.com/oraclize/ethereum-...
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2answers
240 views

Add html header fields to oraclize query

I want to send an oraclize query as a post function. I use the following syntax: oraclize_query('URL', 'http://...', json_doc). This schema works but without attributes for the html header. How ...
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2answers
675 views

Oraclize pricing in smart contract

Should i have ether in contract account in order to call oraclize_query (firtst call is free) or it discounts from the main account? Thanks!
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1answer
366 views

Oraclize send fee in oraclize_query

I know that only the first call to oraclize_query is free but i don't know how to send the small fee requested. Can you give a code sample ? Thanks!
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268 views

Matlab / R and Ethereum integration [closed]

What is the most efficient integration of off-chain tools like Matlab or R into Ethereum? (in order to do off-chain calculations and reduce gas costs)
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How to use oraclize with Eris [duplicate]

I faced many problems in order to run oracles with Ethereum. I'm thinking of using Eris and I need guide to use oracles with Eris. I need example so i can get how it works. is there any example?
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1answer
448 views

Oraclize + Testrpc + Truffle. Results aren't updating in contract

In my contract I am just doing a basic query to WolframAlpha function testOracle(){ oraclize_query("WolframAlpha", "random number between 0 and 100");} I also have the __callback function: ...
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0answers
223 views

Error in dapp developed using 'Truffle' framework -Smart contract function call won't get executed

I am developing a dapp using 'testrpc' and 'truffle'.I have also used ethereum-bridge for Oraclize.I have written a smart contract function which calls a url using 'OraclizeQuery'. The following is ...
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1answer
300 views

Smartcontract function call won't get executed in dapp developed using 'Truffle' framework

I am developing a dapp using 'testrpc' and 'truffle'.I have also used ethereum-bridge for Oraclize.I have written a smart contract function which calls a url using 'OraclizeQuery'.I have added the ...
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1answer
303 views

How to fetch specific data based on user input from url using Oraclize?

I am using 'testrpc' and 'truffle' for development. The following is the contract code used. pragma solidity ^0.4.0; import "./usingOraclize.sol"; contract WeatherApiCall is usingOraclize { ...
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1answer
437 views

How to display the result returned from Oraclize's _callback function in dapp frontend?

I am using testrpc as client and truffle as development framework.And also using ethereum-bridge for Oraclize. This is the contract code.I have downloaded the 'Oraclize API' (oraclizeAPI_0.4.sol)from ...
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3answers
3k views

Converting oraclize result from string to address

I am trying to set up a contract that gets an ethereum address from a json file using oraclize, and in turn i'd like to send ether to that address. function __callback(bytes32 myid, address result) { ...
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1answer
664 views

How to run contracts with 'Oraclize' using truffle?

This is the contract code.I have downloaded the 'Oraclize API' (oraclizeAPI_0.4.sol)from the Oraclize github repo.I have added this file to the truffle contracts folder, and rename the file to ...
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3answers
14k views

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: https://ethereum.stackexchange.com/a/9825/5892 Smart contract can not ...
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2answers
5k views

Oracle (oraclize.it) with Truffle and Testrpc

As I understood in the blockchain, it is "not" possible to interact with webservices outside the blockchain. This must be done over oracles in order to verfiy that the request is secure, and the state ...
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1answer
2k views

Bitcoin price oracle

Are there any oracles available for Bitcoin price? I'd like to do a currency conversion math inside the smart contract code.
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1answer
959 views

Oraclize out of gas on Ropsten Testnet

Every time I try to run the getPairPrice function in the contract bellow I get an out of gas error. My contract always has a balance before I call the function, 2 ethers to be exact, but I still get ...
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0answers
248 views

Connection between two blockchains

I am looking for an approach to creating a connection between two blockchain-networks. I found out that I can use oracles to get data from extern systems (= second blockchain-network). But how can I ...
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2answers
598 views

ERP systems and Ethereum

I wanted to know the integration state of ERP system (like SAP) and Ethereum. Is there an API that allow a smart contract to fetch information from a ERP to store that data? Thanks in advance Best!
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1answer
637 views

oraclize 'VM Exception: invalid JUMP'

Here is my smart contract that uses oraclize to buy bitcoin with ether. pragma solidity ^0.4.0; import "https://github.com/oraclize/ethereum-api/oraclizeAPI_0.4.sol"; contract BuyBitcoin is ...
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1answer
349 views

Can I add extra data to an oraclize query so that I can use it in the callback function?

I would like to be able to use certain data in the callback of an oraclize query that I want to pass in when creating the oraclize query. Say I have the following function in a contract: function ...
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4answers
2k views

Issues getting a simple oraclize example to work, callback never executed

I have been trying to deploy and test the basic "SimpleDice" smart contract provided as an example from Oraclize. I have had to adjust it to work with solidity 0.4.2 a bit, but maybe I am missing ...
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1answer
785 views

Become your own Oracle? Can you put your own real world data into your Ethereum contracts? [duplicate]

I was reading this link and have a question that I don't think was answered there . I understand that the third party providers act as Oracles and they bridge the gap by putting real world info into ...
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2answers
2k views

Can oracles send data to smart contracts on multiple blockchains?

Can oracle implementations like Oraclize and Reality Keys work with two different blockchains? More precisely, if I have a custom data source and my own oracle running on top of it, can that oracle ...
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1answer
139 views

Aren't oracles extremely data consuming?

I'm a bit concerned that oracles used professionally would need a lot of disk space. The blockchain is not growing rapidly since if a contract didn't change its state, the next blocks state tree just ...
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1answer
2k views

Using Oraclize to assign value to another contracts variable

I'm using oraclize to get the price feed using this code: import "oraclizeAPI.sol"; contract PriceFeed is usingOraclize{ uint public BTCUSD; function PriceFeed(){ oraclize_setProof(...
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1answer
1k views

How to import Oraclize module?

I am trying to follow an Oraclize example, with this source code and compile it using Mist: /* Kraken-based ETH/XBT price ticker This contract keeps in storage an updated ETH/XBT price, ...
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2answers
481 views

Customized oracle to access and make changes to data on a cloud service

Although, there is some literature mentioning the possibilities of oracles to supply external data to smart contracts in a blockchain, I am a newb and was wondering whether there is a successful ...
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2answers
240 views

Oracle service for Eris

In Ethereum, a smart contract can get external datafeed via oracle services. Does Eris also support such oracle services?
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2answers
313 views

What are the most important potential attack vectors on oracles?

Specifically, with my question I want to target Oracelize.it as arguably the most "state of the art" oracle service. This specification is done in order to exclude trivial attacks in the potential ...
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2answers
1k views

How to wait Oraclize result before running code further?

I'm trying to write a contract, which first asks input from user, then makes Oraclize query and after receiving answer from Oraclize compares user input to Oraclize answer. My problem is, that my ...
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1answer
2k views

Why does this Oraclize query only works once?

Why this code works one time? First time I get proper random number, but after that I get wallet response "Data can't be executed, so it will use all provided gas" I'm in Testnet. contract ...
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1answer
1k views

How does “Gas Price Oracle” work?

How does "Gas Price Oracle" work? "Gas Price Oracle" is explained here in go-ethereum wiki, but it doesn't explain how it works. Where does it get the data from? How does it do its calculations?
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3answers
1k views

Smart contracts and IoT: how will they call the physical world?

Ethereum and IoT: if smart contracts cannot contact the "outside world", how will they trigger car unlocks and other things with the "smart" property? An AirBnB example: a smart contract between two ...
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1answer
488 views

Oraclize API not returning anything in Morden testnet

I use Geth 1.3.6 and a Morden testnet. I am trying to test the Oraclize API for my Ethereum smart contracts. First, I have compiled and deployed the simple smart contracts as DieselPricePeg.sol and ...
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2answers
1k views

Contracts as data feed?

The documentation example for a complex bet contract includes a "Weather feed" service. How would such a feed/service/contract work? For a weather feed, either there needs to be a temperature sensor ...