Questions tagged [blockchain]

The Ethereum blockchain is a distributed database based on the Ethereum whitepaper specification and stores both the full transaction list and the most recent state.

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1answer
178 views

How can I show on web3j a list of all the instructors added on my blockchain?

I need to show on an html a list of all the instructors that are set up on the list pragma solidity ^0.4.18; contract Owned { address owner; function Owned() public { owner = msg.sender; } ...
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20 views

Is Egretia (EGT) is still Ethereum Token? Or It has been moved as a Coin to its own Blockchain?

Currently Egretia (EGT) is represented as a Token of Ethereum Network, but is there any changes regarding shifting from Token to Coin on its own Chain?
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619 views

Ethereum wallet/Geth incredibly slow to sync, help?

So I've noticed some people having the issue similar to mine, entitling their post as "very VERY slow to sync" and other variations of that, however they're complaining at around 100 blocks every ...
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337 views

Smart Contract - Update implementation using a Relay with delegateCall

I know that smart contracts are supposed to be immutable and that's the whole point, but to expect someone to implement a logic that never changes (no upgrade or no bugs) from day 1 is also ...
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How to solve this error [on hold]

\?\C:\Users\keval\Desktop\project\dcrowdfund\D-crowdfund\node_modules\scrypt\build\Release\scrypt.node is not a valid Win32 application. \?\C:\Users\keval\Desktop\project\dcrowdfund\D-crowdfund\...
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1answer
256 views

Where does geth store data except for the AppData\Roaming\Ethereum folder?

The AppData\Roaming\Ethereum folder on my computer weighs 5GB, but geth has reduced my disk space by a lot more than 5GB. Where else does it store data?
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1answer
29 views

cannot be able to connect to private blockchain hosted at local VM

I want to use remix IDE and want to connect web3provider which needs to be connected to private blockchain running on VM locally. My system is running on Windows 10 and I am running the VM on my local ...
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1answer
339 views

How ERC20 Token balance are recovered during Ethereum chain rolling-back

My Answer: Ok, the problem is really with Ganache ... If I use geth, everything is alright. ... ... sorry for your time ... ---------------- The Original Question -------------------- My ...
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1answer
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Code:const web3 = new Web3(window.web3.currentProvider) Error: window.web3 is undefined

I am going to connect my contract with the website.However,there was something wrong with the web3? I'm not sure. import Web3 from "web3"; const web3 = new Web3(window.web3.currentProvider); const ...
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1answer
9 views

Encrypted transaction from one account to another on Ethereum blockchain [on hold]

I have to send an encrypted transaction from one account to another in ethereum blockchain. I downloaded Ganache to create the ethereum blockchain. How do I carry out an encrypted transaction? Do i ...
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Web3 - how to add WEI and ETH values correctly

I'm working on an auction feature in my DApp and having problems correctly adding together two WEI values. The contract stores two important values: 1. A minBidIncrement variable - which I've set to ...
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2answers
553 views

How to connect peers which are on different computers in geth on private network?

I am trying to setup a private network and trying to connect peers. Currently I'm trying it on my laptop and virtual machine(VM) runing on the same laptop (both of them are connected to internet). I ...
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414 views

Help-A-Noob-With-Ethereum-Wallet-Blockchain-Download

I'm on a 2013 Macbook Pro / 16 GB ram / 512 SSD / 2.3 GHz I just transferred 3 ETH from my poloniex account to the Ethereum Wallet on my local machine. The thing is, the entire blockchain hasn't ...
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1answer
250 views

Multiple addresses initialization in constructor function

Usually we have one address initialization in constructor function. And that address becomes owner of the contract. While studying erc721 token and going through several examples online i found ceo ...
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1answer
491 views

Deploying Solidity Contract Using Web GUI and web3

Any guide or step by step Tutorial for deploying a solidity smart using a GUI and accessing the meta mask account ? Please Help
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2answers
1k views

Error: gas required exceeds allowance or always failing transaction upon function execution

Problem The transaction fails because the transaction ran out of gas instead of it failing because the require condition was not met. It works fine before the solidity update to version 0.4.24. It ...
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Why is a failed transaction included in the blockchain as a “failed transaction”

According to this highest upvoted answer, "but still include it in the blockchain as a "failed transaction"... What is meant by the term "gas"?
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3answers
253 views

Does Using Infura Breaks Decentralization?

Decentralized applications have a philosophy: they are immutable,secure and trustless applications. You can connect to Blockchain and be sure about that features. Infura is a great tool when ...
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1answer
245 views

How to connect IPC and RPC to transact fake ethers?

I have setup 2 nodes, 1 on testRPC and the other on geth(using cmd and mist). How to sync both the nodes so that I can write a crowdfunding smartcontract for the accounts in both the private nodes to ...
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1answer
22 views

Useful resources to help understand go-ethereum source code

I am new to ethereum community and I want to study the implementation of Ethereum (e.g. geth) and contribute to the go-ethereum project. However, I find the source code hard to understand by only ...
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1answer
57 views

MetaMask - RPC Error: Internal JSON-RPC error

I am getting this error when i trying to use metamask on my local for a simple transaction from one account(say A) to another (say B). code: -32603 data: {originalError: {…}} message: "Internal ...
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1answer
49 views

Network propagation delay and forks in Proof of Stake?

I am learning the fundamental of Proof of Stake (PoS), i came accross a question which i could not find answer to. Assume we have three validators (aka miners in PoW), V1, V2 and V3. Each of the ...
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4answers
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What exactly is an Ethereum client and what clients are there?

What exactly is an Ethereum client? Is it a full network node that can post transactions to the blockchain (if that is the correct lingo?) or could it also be a light JS client that connects from a ...
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2answers
50 views

accessing unpredictable numbers

I see that this has been a widely discussed topic in the past but I still don't understand why the future block hashes shouldn't be used for lottery-type games. As long as the incentive for a miner to ...
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4answers
211 views

Mist / Ethereum Wallet question

I bought a very small amount of ETH on coinbase just to try it, and I wanted to create my own wallet to get it out. However, I've been trying to get Mist working for 3 days and it is always stuck on ...
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1answer
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How to match the data in the struct?

If the Set function receives two inputs 1.["0xca35b7d915458ef540ade6068dfe2f44e8fa733c",50,"ROC","park"] 2.["0x14723a09acff6d2a60dcdf7aa4aff308fddc160c",60,"AU","school"] How can I return all the ...
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1answer
103 views

Can't connect to localhost:8545 while using ethereumjs-testrpc web3?

I am developing a simple Voting dApp by following a tutorial. In this tutorial we are using npm install ethereumjs-testrpc web3 so that we can get the fake nodes of Ethereum. For that i first ...
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1answer
22 views

About send Ethereum Classic (ETC) coin

Need guideline for send ETC coin using web3js,As per documented flow I understand we can access all methods same as ETH but I have query regarding set provider for ETC after that I can connect to ETC ...
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1answer
13 views

In ethereum network how data structured and is every data stored, is public?

Let's say, 3 companies are using ethereum network. Company A Company B Company C Company A put some data, block01 and block02. So ethereum network looks like, Genesis Block -> block01 -> block02 ...
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2answers
368 views

How many tokens are transfered actually when we are using decimals

I have a code below and when I am transferring 1,695,000,000 to a particular address, so actually 0.000000001695 are being transferred. Why is it so? Does that mean to transfer 1.695 billion tokens I ...
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50 views

Unhandled Rejection (TypeError): Election.methods.addCandidate is not a function

//solidity code function addCandidate(string memory _name) public { candidatesCount++; candidates[candidatesCount] = Candidate(candidatesCount, _name, 0); } //App....
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1answer
283 views

Ethereum Solidity smart contract code Input Output Testing

I have written a solidity based smart contract. I need to test the code on web browser and mobile app. Please suggest the steps what I should do to test and execute the code on - Web browser:- I am ...
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2answers
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Is there a way to prevent your smart contract from burning ETH, and sending it to your wallet instead?

So I am writing my own smart contract on remix.ethereum.org, and it is for a token, and in the code, I have written a simple ICO: function() public payable { if (totalSupply >= 1000) { ...
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10 views

Can we treat/launch private ethereum chain ethers as a CryptoCurrency in Market?

Warm Greetings! I have a private ethereum blockchain setup on my server with multiple nodes , Also running mining software to mine blocks and earning private ethers (no value in market). Can i ...
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1answer
20 views

How do I deposit an Ether amount to the smart contract function, namely deposit ? (Metamask version 0.20.7)

I have a problem with using the deposit () function on a smart contract. How do you use metamask 0.20.7 ? const contractInstance = web3.eth.contract(contractAbi).at(contractAddress); contractInstance....
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488 views

how to get the hash address of previous block while adding a block into blockchain?

In blockchain every block is having three things, Hash address of the previous block Hash of the all the transactions those are part of the current block Nonce, a random value which can be got ...
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1answer
21 views

Two smart contracts interact can't pass value when I using web3.js

I have two different smart contracts interaction_1 and interaction_2 I input the data(team) from remix ide. What I want to accomplish is when user input team in user_input function at interaction_1,...
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1answer
16 views

Can I call someone else's public function/contract

Still new and learning. Forgive me if this is a stupid question. Since all contracts are uploaded to the same blockchain, if I wanted, could I use someone else's public contract in my own front-end ...
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36 views

How to print the value of a Struct ?(mapping)

If the set function receives two inputs 1.["0xca35b7d915458ef540ade6068dfe2f44e8fa733c",50,"ROC","park"] 2.["0x14723a09acff6d2a60dcdf7aa4aff308fddc160c",60,"AU","school"] How do I display the ...
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1answer
236 views

ethereumjs-wallet/hdkey is no more in npm

how to generate multiple addresses from single mnemonic? var hdkey = require("ethereumjs-wallet/hdkey") var bip39 = require("bip39"); // You can generate a mnemonic seed with bip39 library var ...
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2answers
47 views

Integrate more then one user with one ethereum account

I have many users inside the organization and I want to use same ethereum account for all the users , but with different usernames, so it there anyway to do that ?
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676 views

signing a transaction on web3js with private key and broadcasting to nodes

I am having an issue with ethereum based project. I made web3 API to communicate to the blockchain. I did this two ways. both call the same function on same address: METHOD 1 (Using Unlocked ...
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1answer
390 views

Mist: how to view private key of an account

Question: How do I use Mist to extract the Raw private key of an account. The account is password protected (if that makes a difference I don't know). Elaborating: I made an account with mist that ...
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2answers
77 views

How to build the seamless bridge between two blockchain platform?

How to build the bridge between two different consensus blockchain platform? use case: 1.we need to ensure visibility of the transaction in both platforms to assure its integrity When a smart ...
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1answer
15 views

How can I find the block where a user enacted a certain event on a contract?

I'm trying to build a web3.py program to take in a given user's address, and return the amount of ETH traded since they added liquidity to a Uniswap exchange. Uniswap is a smart contract on the ...
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2answers
78 views

Check when a block is mined

Is it possible to know when a block is mined? Is there any timestamp or event/subscription?
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34 views

I Call SmartContract Token ERC20, Why Show Hashing Output ? (Web3 + Metamask + Javascript)

I do not know why with this, even though in the previous version (web3 + Metamask) can issue real data. But now used as hashing (output). I took the example in the code and output below (to get the ...
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2answers
384 views

Deploying a smart contract using DApp

I am new to the development of DApps on ethereum blockchain. I want to make a contract Management System in which users can generate their own tokens and crowdsale using my web application. I am able ...
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1answer
1k views

I sent PRL token to contract address instead of wallet address

I am wondering if i can recover the tokens. I sent PRL tokens to contract address 0x1844b21593262668B7248d0f57a220CaaBA46ab9 instead of myetherwallet address from kucoin exchange wallet. :-( Are ...
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1answer
544 views

How to get multiple values from one function contract to another

I have two contract and in first contract it contains a function which is responsible for returning two values, one of string and one of integer. function getUserData(address userAddress) public ...