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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1answer
446 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
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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
674 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
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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
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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 ...
6
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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
980 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
251 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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3answers
679 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
649 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 ...
2
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1answer
365 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 ...
4
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1answer
796 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
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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 ...
3
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1answer
144 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
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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, ...
6
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2answers
496 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
247 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
328 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 ...
8
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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 ...
15
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1answer
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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
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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 ...
6
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1answer
495 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
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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 ...
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1answer
630 views

How does Codius differ from Ethereum?

Codius is one of smart contract platforms by Ripple which project is unfortunately suspended. What did they try to do with Codius? How does it differ from Ethereum?
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2answers
793 views

Can't get oraclize to work

I have tried running programs with oraclize on the ethereum testnet (Morden). My program fails to compile due to import "dev.oraclize.it/api.sol" error. I have therefore tried to manually download ...
20
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3answers
5k views

How does Oraclize handle the TLSnotary secret?

Oraclize claims to offer a provably honest secure retrieval of a webpage by taking advantage of TLSnotary (a service that allows an auditor to verify if a specific web page was accurately retrieved) ...
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6answers
29k views

How can an Ethereum contract get data from a website?

What is the process/workflow behind the process where an Ethereum contract gets some data from a website?

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