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.

Filter by
Sorted by
Tagged with
3
votes
2answers
44 views

Could the Oraclize _callback function be run twice by the same query?

An example _callback function from Oraclize: function __callback(bytes32 _queryId, string _result, bytes _proof) { if (msg.sender != oraclize_cbAddress()) throw; if (...
1
vote
1answer
179 views

Using smart contracts for delivering encrypted data [closed]

How can I utilise (perhaps automate) a smart contract to deliver some encrypted data from A to B, based on the pre-requisite that A fulfills B's requirements. Would I need an oracle for this type of ...
2
votes
2answers
102 views

How to limit N bytes to value range using Oraclize Ledger-Proof Random Number — unfair raffle

Lets say you have 50 tickets to a raffle. You choose to return 4 random bytes from the ledger proof RNG(https://github.com/oraclize/ethereum-examples/blob/master/solidity/random-datasource/...
0
votes
1answer
108 views

Error during Testing Contract using Ethereum-bridge for oraclize

I'm getting the following error when I'm trying to test (truffle test) my contract which uses Oraclize API 0.5 to get the ledger random from oraclize (datasource = "random"). I'm using solidity 0.5.0 ...
2
votes
2answers
186 views

Breaking one large contract to multiple smaller contracts

I'm building a project which has the following artifacts: the complete code for Oraclize API, inline, (1329 lines of code including comments and description) SafeMath Library, inline, (114 lines of ...
0
votes
1answer
44 views

Oraclize a restfullAPI using a specific number represented by the variable z for a custom token (remix)

is it possible to pass an integer (in this case 141) represented by the variable z from a certain restfullAPI into the custom token function: balances[msg.sender]? So in the end I want to have my own ...
2
votes
1answer
78 views

Oraclize a restfullAPI using a specific number represented by the variable z

Hello I made a restfull API on my own (python file jsonify + localtunnel) on a localhost using a specific number (in this case 141) represented by the variable z. This variable should go into DevCoin ...
-1
votes
1answer
70 views

I want to oraclize this smartcontract to get some output on a localhost. I am desperate what should i do?

pragma solidity ^0.4.17; import "installed_contracts/oraclize-api/contracts/usingOraclize.sol"; contract DevCoin is usingOraclize { mapping (address => uint256) public balances; event ...
0
votes
2answers
74 views

CallBack function is not triggerring

I have this contract. pragma solidity >= 0.4.0; import "./oraclizeApi.sol"; contract USDPrice is usingOraclize { string public price; address public owner; event Log(string text); ...
2
votes
0answers
51 views

ethereum-bridge: always return a callback error [closed]

I am using Oraclize for generating random number for my smart contract. I write unit test for testing oraclize things so I use ethereum-bridge written by Oraclize. Here is my problem: First: my smart ...
4
votes
1answer
107 views

How to raise version of oraclize-api installed via Truffle

I'm using local instance of Oraclize API, to make truffle compile work. I've installed it by truffle install oraclize-api but for now, I'm getting following error if (oraclize_randomDS_args[...
1
vote
2answers
358 views

Chainlink vs Oraclize [closed]

I am trying to choose between Chainlink vs Oraclize. Can anyone advise the difference between both solution? Nathan Aw
1
vote
2answers
111 views

Oraclize callback not firing on Ropsten

Testing out oraclize for a smart contract. function __callback(bytes32 _myid, string result) public { if (msg.sender != oraclize_cbAddress()) revert(); // emit LogOraclizeID(bytes32ToString(...
1
vote
1answer
19 views

Request and compare API Reponses in Oraclize call

I want to send requests to 3 Weather APIs and compare their results like if the rainfall at a specific day were the same London to avoid the single point of failure. I already learned how I can send ...
1
vote
1answer
61 views

How to test time-dependent contracts on the mainnet?

In Ganache, I use evm_mine to simulate the passage of time. Assuming block times are accurate enough, what are the best practices to test some contracts on the mainnet or a testnet which depend on ...
0
votes
2answers
84 views

What is the max data and program complexity one smart-contract can support

I want to make a smart-contract for P2P trading. I am wandering if I have to create separate contracts for each bid and agreement between two entities, or I can simply create a single contract that ...
1
vote
0answers
58 views

How to handle Oraclize if it's failed?

I'm using the Oraclize to get the random number for bets. When the function bet() is called and if the oraclize is failed it should call the pingOracle() again. Below is example function bet() public ...
0
votes
2answers
47 views

Storing private data that will be decrypted by a smart contract

Another private data problem! I would like to store some data in a Smart Contract, encrypted so nobody can see it upon some specific condition (time, or whatever). For instance, after one year, this ...
0
votes
1answer
48 views

Is there a more “decentralized” way to verify an Ethereum account owns a particular Twitter handle?

Is this something fulfilled by a project like uPort? Basically, I need a way in my contracts to verify that a particular Ethereum address (0xasdf...) and a particular Twitter handle (@user) are ...
1
vote
1answer
111 views

Parsing the WolframAlpha string result from the Oracalize __callback function into a usable format?

I need to generate 10 unique random numbers between 0 to 100 in my smart contract. For this I've decided to utilise Oracalize and one of the datasource called WolframAlpha. This is how I use it: ...
1
vote
1answer
81 views

Truffle fails to migrate an Oraclize contract into Ganache

I have a contract that is using Oraclize. When deploying the contract from the Remix IDE into Ganache/Ethereum-bridge via MetaMask, the contract is fully functional. However, when trying to migrate ...
2
votes
1answer
74 views

Can i change data in a database using smart contract and oraclize?

i understand that smart contract and oraclize can be use to get data from a database but can i manipulate the data inside the database using smart contract and oraclize? If so how can i do it? Can I ...
0
votes
2answers
42 views

Oraclize: Mismatching queryId and myid

I have the following contract that uses Oraclize: contract Test is usingOraclize { bytes32 public query; mapping (bytes32=> address) senderAddress; address public resultAddress; function ...
2
votes
1answer
103 views

Using oraclize and solidity-util - having trouble splitting string separated by space

I am learning to use Oraclize to connect it to random.org to generate random numbers. Here's my test contract code: pragma solidity ^0.4.25; import "github.com/oraclize/ethereum-api/oraclizeAPI.sol"...
0
votes
1answer
27 views

Changing the contract state while waiting for the Oraclize __callback()

I have a contract that uses Oraclize to query some data. When the query is sent, a global variable address is set to the msg.sender. This is to be able to interact with the query sender in the ...
1
vote
2answers
282 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 ...
1
vote
1answer
125 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 ...
1
vote
2answers
156 views

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)?
1
vote
1answer
100 views

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://...
2
votes
1answer
187 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 ...
0
votes
1answer
134 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 ...
0
votes
1answer
82 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? ...
1
vote
0answers
37 views

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 ...
1
vote
2answers
63 views

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 ...
3
votes
1answer
382 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?
2
votes
2answers
444 views

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 ...
1
vote
0answers
134 views

“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 ...
1
vote
3answers
869 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" ...
3
votes
0answers
38 views

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 ...
1
vote
0answers
35 views

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 ...
1
vote
2answers
80 views

“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" ?
6
votes
2answers
570 views

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" ?
1
vote
0answers
61 views

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 ...
2
votes
1answer
97 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 ...
0
votes
2answers
107 views

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 ...
0
votes
0answers
43 views

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 ...
2
votes
1answer
128 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 ...
0
votes
1answer
509 views

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 ...
4
votes
2answers
436 views

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 ...
3
votes
3answers
121 views

Ways to Decentralize Oraclize

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