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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How is Ethereum Virtual Machine (EVM) isolated (sandboxed)?

I always had this question in mind: What are the used technologies, in order to achieve the isolation of the EVM? does it just run as an isolated process in its own namespaces using the linux feature ...
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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How smart contract transactions work?

I read that smart contracts don’t have a private key, so they can’t sign a transaction. My question is: when a smart contract starts a transaction to an EOA, how are we sure that the smart contract ...
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How to deploy a DAO on Ethereum?

Want to deploy and operate a Decentralized Autonomous Organization (DAO) on Ethereum. What are my options?
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How to build a decentralised Voting Website without using any 3rd party extensions like Metamask, or IDEs like Remix? [closed]

I've gone through various Blockchain Tutorials but everywhere it's one or the other same thing. Download truffle/ganache, from 10 free testrpc account, use one, use metamask, Remix IDE etc, and Voila!...
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Ethereum as a private network is possible? [closed]

can i deploy a private network like the way it does other private blockchains with Ethereum ? and the test networks in Ethereum only work for public right or can i deploy it there ?
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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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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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Fatal: Account unlock with HTTP access is forbidden! [duplicate]

I'd been following a tutorial about How to make your own local blockchain, everything was fine until i shoould run the next script: geth --networkid 22773 --mine --minerthreads 1 --datadir "~/home/...
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Migrate Database

I want to migrate my no-SQL dB on-chain. There are two options as far as I know: Store the objects in the form of string using a simple smart contract. Create a structure to implement the dB schema. ...
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Can we pass string values to the contract which holds bytes 32 only in solidity?

My contract can hold only array of type bytes32 only. How can we store string values as well?
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Contract address is not shown in rinkeby testnet etherscan

I am using Getch with truffle framework and i created an account. I have Migrations and Election.sol. After i can migrate, i couldnt see it in etherscan website. Although truffle migrate --reset --...
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Gas required exceeds allowance truffle migrate

Hi i am trying to work truffle migrate and firstly it start to Migration.sol and then Election.sol. When start to deploy ELection.sol it throws following error. What should i write gas:270000 instead ...
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Returned value arent valid did it run out of gas?

After migration command line (truffle migrate --reset --network rinkeby), it is deploy. However i couldnt see at etherscan website when i enter the contract address. Should i see? Whatever then i ...
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Truffle migration takes too much time and dont migrate

0 Hi i am trying to migrate contract by using getch on oracle virtual box ubuntu. Although 1_initial_migration.js deploying it shows Block: 0 Seconds:16743 and it is not completed to deploy and also ...
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MetaMask blocks Web3 requests

I just set up a Block Explorer to interact with my private blockchain. The private Blockchain runs in a VM. The host system connects to the Block explorer (also on VM). When I have meta mask ...
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Are the timestamps of blocks for Ethereum only accepted when they are monotonically increasing?

Are the timestamps of blocks for Ethereum only accepted when they are monotonically increasing? If yes, why? And why other blockchains like Bitcoin and other blockchains with shorter block time can ...
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Load Smartcontract in Nodejs

I created the server based on golang. This server can load smart contract that is deployed using its address. It works on my local machine, but it does not work on EC2 instance. So I decided to ...
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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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Why am I getting a Parse Error in my smart contract after the constructor?

I'm writing a token sale smart contract & my original error was my function had the same name as the contract and I changed it to a constructor because the contract cant have the same name as the ...
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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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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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Which Protocol is suitable if I want a validated person to authenticate the block?

I want to create a system in which Every user will have some specific authorities. Like Examination will validate the block containnig Student Marks. Finance should have authority to add block ...
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How to do the Smart Contract Storage Migration using Quorum?

I wrote one smart contract without upgradable logic, now I want to update the same smart contract with some changes. Is it possible to copy the data from old contract storage to a new one?
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How to Read Construction information?? (from blockchain develpment with go)

pragma solidity ^0.5.10; contract Simple{ uint256 data; string male; string name; string id; function getdata() view public returns(uint256) { return data; } ...
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“The bigger the block size, the greater the computational power needed to mine a block” Does this make sense?

I was going through one of the papers and the authors in the paper mentioned this statement. I am not able to find the correlation as such. I do understand that Larger blocks may propagate slower ...
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Can anybody Point out the Difference between Web3.eth.sendTransaction and web3.eth.signTransaction?

Do we need to sign the transaction by web3.eth.signTransaction after initiating transaction via web3.eth.sendTransaction. for example: when I do: web3.eth.sendTransaction({ from: accs[0], ...
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Error: Keystore: Must include seedPhrase in createVault inputs. How to fix?

i'm studying blockchain development, and i'm trying to create wallet with seed words using eth-lightwallet and vuejs. But i receive this error: Keystore: Must include seedPhrase in createVault inputs, ...
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How to copy the data from a running private network to another

I have two seperately running private ethereum networks,i want to copy the data from the first private network to the second one without stopping.I have tried multiple ways but was not successful.I ...
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Can I Create Node.js API for each function in Smart Contract but sign a Transaction from frontend via Metamask.?

I am trying to develop a Dapp with nodejs backend but I cannot get accounts from Metamask which resides on my frontend. I tried to create an endpoint for each function in Smart Contract. And it seems ...
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How to find out the number of Validators of a transaction if i have its transaction hash

I want to find out how many validators have validated my transaction.My transaction has is 0x051430dc5cd84c44954e43b25f8709c9c1a1c634f384ec6dd7610f6f945732e1 can anyone tell me how many validators ...
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Data encryption

Since all data on the Blockchain is public. Presume I have multiple users submitting data which I want to hide, is there a way I can encrypt that data on the Blockchain ? Or do I have to encrypt off-...
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Get Submitted Data from Blockchain

I'm using a html code connected to my smart contract via testrpc node, where users submit temperature data. How can I view that data from the smart contract, each time I view from the contract I see ...
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node cannot be made up in private blockchain by using command line

I have created the genesis.json The genesis json content is { "config": { "chainId": 46860, "homesteadBlock": 1, "eip150Block": 2, "eip150Hash": "...
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Relationship with smart contract and block confirmation

I have known Bitcoin need 6 blocks for confirmation. However, In ethereum, It is different depend on clients By this post What number of confirmations is considered secure in Ethereum? It takes ...