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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89
votes
6answers
28k 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?
38
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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 ...
20
votes
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) ...
21
votes
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 ...
7
votes
1answer
350 views

Non Deterministic External Service Call

As per the basic rules of blockchains believe it is mentioned that no service call from the smart contract should be made where the result is non deterministic. What I understand is if the result is ...
6
votes
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.
3
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1answer
756 views

Simplest way to use a variable in an Oraclize query?

I have a variable number in my Solidity contract which changes and I need to incorporate this into an oraclize query. My oraclize query looks like the following: oraclize_query(60, "URL", "json(https:...
15
votes
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?
6
votes
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 ...
4
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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?
3
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1answer
771 views

Why isnt Oraclize working?

I just opened up the Oraclize website and copied their 'Quick Start' ethereum contract and pasted it into Solidity online compiler to try it out (environment is Javascript VM). When I change the value ...
8
votes
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 ...
8
votes
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 ...
5
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1answer
627 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?
13
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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 ...
8
votes
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 ...
6
votes
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(...
2
votes
1answer
68 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
vote
1answer
415 views

Oraclize with private blockchain - generate custom address for OAR

I am new to Oraclize. I am integrating a private blockchain with Oraclize. It says in the ethereum bridge document Add OAR = OraclizeAddrResolverI(EnterYourOarCustomAddress); to your contract ...
0
votes
1answer
769 views

How Oraclize and API call works

I have read the Oraclize documentation: https://docs.oraclize.it/#home and similar topic like: How do oracle services work under the hood But is still have a question, take this example: I have a ...
0
votes
1answer
130 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 ...
5
votes
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
votes
2answers
782 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 ...
4
votes
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) { ...
2
votes
1answer
384 views

How to encrypt an API key if using oracalize for some API in a smart contract?

In my smart contract, I want to use the random.org API to generate a random number, but when publishing the verified source code I don't want anyone to see what API key I'm using. The etheroll ...
1
vote
1answer
152 views

What is the Oraclize public key?

I am using Oraclize in a smart contract and want to encrypt my API key. According to http://docs.oraclize.it/#ethereum-advanced-topics-encrypted-queries there is a python script from Oraclize that is ...
1
vote
2answers
942 views

Convert string of integers separated by a delimiter to integer array in Solidity?

Using Oraclize, I request a some external data in the form "1 2 3", i.e., space-separated integers (OR any other delimiter). Indeed, these numbers could be requested one at a time, but this would be ...
1
vote
2answers
428 views

“Key not found in database” ethereum bridge error

Trying to perform a basic query using ethereum bridge / ganache / truffle. I appear to have Ethereum bridge running correctly. iPod-Classic-3:ethereum-bridge benandre$ node bridge -H localhost:7545 -...
1
vote
1answer
259 views

How to invoke multiple oracaliszed queries from a single contract

I want to invoke 2 different orcalized queries from the same contract. I saw a few posts but none of the answer works. Is there any way we can do that? Here is my contract. I was expecting this ...
1
vote
0answers
144 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....
0
votes
0answers
104 views

Private BlockChain - Cons?

Plan to implement private chain based on PoA to overcome transaction speed and privacy issue. Q1. what is the expected TPS? any advice to increase it? Q2. Understand that we can still leverage tools ...
0
votes
1answer
259 views

Can't set gas limit for oraclize callback function higher than the default 200000

Could you please help me with the following. I am using OraclizeIt (https://github.com/oraclize/ethereum-api) to retrieve a JSON from some other service via REST. Basically the smart contract method ...
0
votes
2answers
30 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 ...
0
votes
1answer
51 views

Apparent mismatch between Oraclize CBOR and python3 CBOR encodings

I encoded a value using the Oraclize CBOR library like so: Buffer.buffer memory cborArgs; Buffer.init(cborArgs, 64); cborArgs.startArray(); cborArgs.encodeUInt(10); cborArgs....