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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226 views

Retrieve and store data into a local database using smart contract

For my information oraclize can be use to retrieve data from several data source but what if i need to get from a local database such as oracle,sql, etc. Is there any way of doing it? PS: I am ...
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95 views

Storing Mutliple Oraclize Queries

We have been trying to use a mapping to store multiple Oraclize queries and their results but it does not seem to be working properly. What is the ideal way to store multiple Oraclize queries by their ...
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How to use fiat exchange rate oracle in DAPP?

my team is trying to develop a DAPP about fiat exchange rate. How to get the latest fiat exchange rate (USD/EURO etc.) accurately from external Oracles(Or are there better ways doing this)?
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Oraclize handling long response from cryptocompare

I have very custom task and I need to make sure what are limits of each technology. I haven't found nothing similair in this forum yet. I am using Oraclize to get response from this url: https://...
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146 views

Oraclize callback is not called with more data in it

I have very strange experience with Oracle. When I try to add functionality inside of callback, callback is not called, but when I delete functionality callback works without problem. I tried to ...
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87 views

Tutorial to understand technical details of Oracles in Ethereum

What is Oracles? Why is it needed? Is there any good technical blog with an example in which Oracles is explained? From whatever I read about Oracles Oracle is a trusted third party API from ...
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1answer
57 views

Updated: How to interact “directly” with smart contract via a micro-controller?

Assume we have a micro-controller and it collects a meta-data (ex. a payload as a string). How this micro-controller can interact "directly" with smart contract to write this data to the blockchain? ...
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Tutorial for ZAP inegration with Oracle

Oracle is a trusted third party API from which smart contract will fetch the data. Zap is a way to monetize the data which smart contract is getting using a token called zap token. Is there any ...
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How accurate are Etherscan's internal tx's on Rinkeby for Oraclize calls?

I'm trying to optimize my smart contract and am breaking down where the gas is being spent. Each execution for one function costs me about $5 in gas. I looked at Etherscan and in the internal tx's it ...
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336 views

oraclize price for random value too high (rinkeby)?

Currently, when I call oraclize_getPrice("random", 400000); I get back 8000000000000000 on rinkeby. That'd be over 2$ USD if on the mainnet and also looks oddly round. Why is this so high?
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Who is Oraclize? Is using their API dangerous?

I looked through the code of the oraclize api, and it seems that oraclize can swap out keyportions of the implementation at will. In particular, it looks like they can adjust the pricing for their API ...
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“Augur” vs. “Oraclize” : What is the main difference?

Can we say that "Augur" is a decentralized Oracle against "Oraclize" as a centralized model? I mean can we consider Augur as a decentralized Oracle and on the other hand, Oraclize as a centralized ...
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657 views

What is the Oracle Problem definition exactly and briefly?

What is the Oracle Problem definition exactly and briefly? Does it mean "trusting on a centralized Oracle" ? Or "How to reach a consensus between a group of Oracles" ? Is the matter "centralization" ...
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Oraclize random datasource, what is trusted by using it?

I'm currently looking into ways of accessing randomness in a smartcontract. I found oraclize random datasource https://github.com/oraclize/ethereum-examples/tree/master/solidity/random-datasource and ...
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How to know the price of the day of ETH in USD by Oracles?

Consider in a contract the payer intends to pay recipient ETH based on USD (ex. the salary is 1 USD but paid by ETH). So, if today contract needs to know equivalent value of 1 ETH in USD exactly at ...
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“Augur” : Is it an “Oracle” or “data-source” ? which one?

If we define following three entities (as defined HERE): (1) data-source (2) query (3) the oracle/oracle network Then, as this article says, is "Augur" a data-source ? Or it is an "Oracle" ?
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Is it possible to use “Oraclize” on a testnets such as “Ropsten” or “Kovan” or “Rinkeby” or even local blockchain such as “TestRPC”?

Is it possible to use Oraclize on a testnet such as "Ropsten" or "Kovan" or "Rinkeby" or even local blockchain such as "TestRPC" ?
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How do we deploy a smart contract with Oraclize to Rinkeby Network?

I have created a smart contract with Oraclize logic which I tested locally using Truffle. Now I want to test it on Rinkeby network along with my front end, what it the process to do so ? How do we ...
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84 views

question about gas limit when using oraclize

I'm using oraclize to fetch some data from the outside world. Oraclize calls the __callback method of my smart contract. For this call oraclize have to pay gas and there is a function to set the gas ...
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Detecting oraclize completion for front-end update using Web3.js

I am using oraclize-api to fetch and store twitter posts into a smart contract. Posts are placed into a mapping using the twitter id as the key (i.e. <username>/status/<id>), and the tweet ...
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Dapp design to handle delay in callback response from Oraclize

In my dapp design I am receiving few user inputs via a form and passing them to a smart contract. Inside the smart contract I am using Oraclize service to timestamp the user inputs. Its a known fact ...
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102 views

How to pass parameters to a function that is invoked from inside of Oraclize Callback function

In the design of my dapp I am using Oraclize to get current time. Now from its __Callback function I want to call another function to which I need to pass other parameters as well along with current ...
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How to get oraclize to work?

I tried to run the code in http://dapps.oraclize.it/browser-solidity/#version=soljson-v0.4.24+commit.e67f0147.js but I get the error VM: out of gas when I try to run the updatePrice function. I set ...
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Capturing an event fired from a contract that was called from another contract

I'm trying calculate tax on arbitrary items/values. To do this I have a single contract is used as an 'Oracle' to get the tax from an external system. This contract defines functions to be called from ...
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Ways to Decentralize Oraclize

Based on my understanding, Oraclize is a centralized solution. What are some ways to decentralize Oraclize?
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115 views

Unable to deploy contract that uses Oraclize. Out of gas

I'm trying to deploy a smart contract that uses Oraclize on the Ropsten TestNet using truffle. It seems that deploy the Oraclize api contract (imported by my contract) it's too costly and causes the ...
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1answer
263 views

Quorum Smart Contract Avoid State Changes External Calls (Oraclize) - Deterministic

One of the Solidity best practices relating to external calls is to avoid state changes after an external call. However, does this principle still apply if one is using a private blockchain such as ...
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311 views

oraclize calling a REST API

I am trying to call a third party REST API that I developed using spring boot, and I want to call a function(param1,param2) in the API from the oracle using the oraclize_query() (POST request), but I ...
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1answer
122 views

Solidity: chaining multiple functions

I have a contract that uses Oraclize to query some bits of data. Basically, I have the following three functions: getData() - calls Oraclize contract to query data, __callback() - called ...
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143 views

Solidity Oraclize error

I am learning to use oracles in solidity and I have taken this code to see how it works. But I get the following error: "VM error: revert. revert The transaction has been reverted to the initial state....
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358 views

Oraclize: callback contain no result Error

I have the following contract to get a random number from 1 to 6 from random.org: pragma solidity ^0.4.0; import "github.com/oraclize/ethereum-api/oraclizeAPI.sol"; contract RandomOrg is ...
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114 views

How are encrypted Oraclize queries protected against replay attacks, precisely?

The Oraclize API allows users to encrypt a query or part of a query using their public key "to protect data from public scrutiny," to quote their documentation. The documentation has this to say ...
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Does running a Geth RPC server locally also require having a full Ethereum node?

I've been trying to learn about smart contracts and attempting to work through a few examples. Specifically, I found this one about creating an Oracle -- https://github.com/axic/tinyoracle. The ...
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Confirm Oraclize is not working on Ropsten? (No callback returned)

I have a contract on Ropsten testnet that was working fine up until 2 hours and 30 minutes ago. I don't believe it is an error on my side because the code hasn't been changed or redeployed. You can ...
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143 views

Oraclize: oraclize_newRandomDSQuery always reverted

I'm using oraclize for generating random number for my smart contract. I have tested successfully with 2 methods: Using WolframAlpha Using random.org service But when I try oraclize_newRandomDSQuery....
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252 views

Oraclize: Difference between random methods

I write a smart contract and want to use oraclize for getting random number. Are there any differences between those methods: Using WolframAlpha: oraclize_query("WolframAlpha", "random number ...
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1answer
233 views

Im using Oraclize to get a random number but the N of bytes confuses me

It seems like when I give the Oraclize query a N of 4, it always returns a 19 digit number, this might be a coincidence but I think not. What if I actually want a number between lets say 0 and 10 * 10^...
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1answer
163 views

What is the most efficient way to parse a string of integers to an array?

I perform an Oraclize query on an XML file, and receive this string in return: ["31", "25", "24"] What would be the most efficient way to parse through this string and store the numbers into a uint8 ...
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35 views

How does Ethereum handle undeterministic results from oracles?

Since when a transaction is done, every node in the blockchain runs the smart contract in their machines, what if the smart contract is calling an oracle to get a random value? Shouldn't it return ...
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200 views

Oraclize doesn't return an answer

I have a problem when I call the function selectWinner(), send some ether with it to pay for Oraclize. I am using Rinkeby with Infura and metamask for the test accounts. I get an error in the meta ...
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It seems like oraclized takes way more than $0.05 [closed]

When a TX for a random number like such: https://ropsten.etherscan.io/tx/0x54fa389796fea546ac6562bec7cfe4b0daca1b744920a38a0e85036b07a1e0ee It says that 0.004 ehter was send to oraclized and it is ...
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1answer
101 views

Oraclize random number only works once, then doesn't trigger events and requires a lot of ETH

So I am using the following code contract Damble is usingOraclize{ function Damble() { getRandomNumber(); } function __callback(bytes32 _queryId, string _result, bytes _proof) { if (...
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1answer
170 views

Is there any way to only encrypt the api key in a GET oraclize query

I am building a contract that uses oraclize to query an API. The API only accepts GET requests (no POST) and also has authentication that requires an API key to be sent as an argument(query_token) in ...
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1answer
139 views

No response in fetching ETH to USD current rate?

I'm trying to fetch the current ethereum to usd rate from following link: https://api.infura.io/v1/ticker/ethusd This is my code snippet pragma solidity ^0.4.11; import "github.com/oraclize/...
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181 views

Solidity import Tensor Flow Libraries?

Like how we import oraclize in Solidity (as follows), is there some way to import tensorflow libraries for machine learning purpose? import "github.com/oraclize/ethereum-api/oraclizeAPI.sol";
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39 views

Guarantee of good's delivery via Smart contract

Assume Client A wants to sell a package to client B. How should I write down a smart contract that prevents from B to receive the package while being refuse to pay in a claim that he isn't receive ...
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1answer
133 views

Testing ethereum smart-contracts that work with oraclize

I'm new in Ethereum and I have a smart-contract that receive exchange rate from API through oraclize. But I have problems with testing my smart-contract. For testing I use truffle + ganache. Could ...
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1answer
37 views

Should I include API Key in query to avoid rate limiting?

I'm writing an oraclize query that contacts an endpoint that has a limit of 50 requests per day. Does oraclize only have one server and as a result will it get rate limited and start returning errors? ...
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1answer
179 views

Truffle install oraclize

I am trying to install oraclize with truffle. When i run 'truffle install oraclize', I get an error: Could not find suitable configuration file. I am using truffle v4.1.7 Thanks in advance..
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188 views

Implementation of Oraclize API connector

Can someone explain to me how, where, and when is the https://github.com/oraclize/ethereum-api/blob/master/connectors/oraclizeConnector.sol deployed to ethereum blockchain ? This is the implementation ...