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 to fix transfer in etherum

$ truffle test Using network 'development'. Compiling your contracts... Compiling ./contracts/DappToken.sol > compilation warnings encountered: /home/geet/toke_sale/contracts/DappToken.sol:39:...
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Contract is failing on approve function in Ethereum with Solidity [on hold]

My contract file is this http://prntscr.com/pvvkme. My Test file are these http://prntscr.com/pvvkme & http://prntscr.com/pvvlmg My migration file is this http://prntscr.com/pvvm5b My errors are ...
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error in remix IDE

I am facing this type of Error in 'remix IDE' while connecting it to 'web3.js@0.20.2' Error: Failed to decode output: Error: insufficient data for uint256 type (arg="", coderType="uint256", value="...
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Payana decentralized [on hold]

Message: Hello support i have a question and clarification on you, is it true that payany (DPA) company has reserve pool of 80% of there total funds will go into etherium blockchain? Because i am one ...
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web3.eth.contract not working

I have web3@0.20.2 installed using npm . when I call web3.eth.contract() it says that it is not a function and when I use new web3.eth.contract it says it is neither a constructor. This is my code &...
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IPFS file uploading issue [on hold]

I just installed IPFS version 0.4.22 on my Mac. When I try to upload/add a file in TERMINAL - using the following command: ipfs add myLogo.jpg I get this error: Error: ipfs repo needs migration ...
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How to substitute attributes instead of roles in access control coding for solidity?

Say, the role-based access control consists of two roles. But if I want to replace the roles to maybe location and time, how to go about it?
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Does Geth provide a private or public network?

I'm new to the Blockchain world, lacking experience and I'm looking for some assistance. I'm just syncing with ethereum network by using Geth and rinkeby network. by using this command: geth --...
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uncaught ReferenceError: $ is not defined at index.html:72 “ while loading webpage ”Welcome to escrow dapp" [closed]

I am getting javascript error " uncaught ReferenceError: $ is not defined at index.html:72 " while loading webpage "Welcome to escrow dapp". It points me on this line : $('#contract-form').submit(...
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Ethereum development environment for Windows 10

I am new to Ethereum and Solidity. Currently learning it from youtube videos and some blogs. So far I have been doing stuff in the remix IDE on a browser. Now I want to perform the same things on my ...
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How to write smart contract to check deployed owner is intitiating the contract or not, everytime?

I want to write a smart contract where it would check it is owner of the deployed contract is trying to instantiate the contract or not. And by doing to i want to allow only the owner to call smart ...
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How often Geth/Parity access the archive chain files? Can I store remote?

I'm running a full archive node to receive and send funds (ETH & other tokens also). The size of the blockchain is very large, so I'm thinking about storing it remotely and mount as an sshfs ...
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Consortium vs. Permissioned Blockchains

I hear these two terms interchangeably Consortium Blockchain and Permissioned Blockchain. Are they the same? If not, can you please show the difference between them. P.S. Since there exists no ...
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CI/CD principles for creating an ethereum network on Cloud

I am setting up an ethereum network on the public cloud. Are there any specific CI/CD principles specific to Ethereum which could be implemented while setting up Ethereum Network on Cloud? Also, are ...
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getPastEvents on localhost is not a function error

Now, I'm working on an Ethereum Blockchain project to transfer the ownership of stored devices by using local web3 provider at the truffle environment. Truffle v5.0.27 (core: 5.0.27) Solidity v0.5....
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Could this work? Proof of Consistency?

So, I have been doing some research on Blockchain , for my dissertation, recently and had spent a lot of time researching consensus protocols. This had led me to wondering if there is any other ways ...
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Does transaction hash in Ropsten ( testnet) deprecate ever?

I want to know whether transaction hash created in testnet stay forever or after sometime it gets deleted? Like in IPFS garbage collector deletes unpinned files after two weeks. IPFS is also ...
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Why use nodepools or backends?

I have a fundamental question about eth/blockchain infrastructure. I see several posts talking about the need for backend node infrastructure when launching a dapp/ smart contract. This infrastructure ...
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Invalid sender address, failed to deploy a transaction to the blockchain network

Description I'm trying to deploy a contract to rinkeby network, but everytime I like to deploy the contract it throwing error as invalid sender. Compile code const path = require('path'); const fs =...
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How to change push() method to simple code?

I have this code but it's static and I wanna change it dynamically. function addCandidates(){ if( own == 1 ){ candidate[0].candidate_ID[0] = 1; candidate[0].candidate_ID[1] = 2; ...
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Quorum-maker-node not starting

I have created a node in quorum-maker using my ip address but that node is not starting.If i create a node using local ip(127.0.0.1), node starts.why?
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Are there any virtual IoT simulators that facilitate the connection with Ethereum Blockchain?

I already built a smart contract for Ethereum Blockchain by using truffle; Now, I'm looking to connect my smart contract with the IoT environment. So are there any IoT simulators (platform, framework,...
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Can we connect custom Ethereum currency through java's web3j library ? If yes then how?

Im trying to create my own new currency using solidity and ethereum platform and also i want to create an Ewallet of my currency using java so that my ewallet could communicate through api .If u ...
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Why do I always get “Returned values are not valid, did it run Out of Gas”?

I'm new on Ethereum blockchain and I'm working on deploy and using smart contract using truffle on my private blockchain. I have followed exactly this guide https://www.trufflesuite.com/docs/...
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Linked contracts not running on go-ethereum

A very simple linked contracts example where A contract has a variable and B contract queries the A contract's variable is running ok on Ropsten+myetherwallet and Remix sandbox, but it fails when ...
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Why my smart contract's function always return 0?

I'm new on Ethereum. I'm trying to deploy my first smart contract in my private blockchain but my function always returns 0. I wrote the simple Smart Contract: pragma solidity^0.5.0; contract ...
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Is QTUM is a coin or a Token?

According to Etherscan Qtum is a Token, holding supply with verified smart contract. But its official site contains its own protocol and integration mechanism. Is it still a token under ETH or it has ...
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How to find out in blockchain ledger the current ownership of asset being transacted

I am new to blockchain and smart contract as well. In smart contract we can only save the current state of any transaction but if we need to know the previously expunged transactional data ie, the ...
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How simulate blockchain and smart contract in VANET?

I am a beginner in the blokchain, I am blocked how I start simulate a blockchain and smart contract in vanet. Can you help me and inform me how I have to simulate blockchain and smart contract in the ...
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validation of data integrity in block

I am learning ethreum dapps development and have developed some dapps. I was thinking about supply chain dapp which i think , is very good application of blockchain as it ensures all the history of a ...
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How Merkle Patricia Trie updates the account balance?

This is my understanding of the Merkle Patricia Trees in Ethereum so far: There are three kinds of merkle trees storing diff info - state, transaction and receipt. When a new block is added it ...
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How to transfer ERC20 token from one account to another account but paying the transaction fee from third account?

I want to transfer token from account A to account B by paying transaction fee from account C.I have tried the following logic but token transfer from contract to contract mean contract transfer token ...
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Failed to read genesis file: open genesis.json: permission denied

First of all I have to say that all this things will work on my windows machine. Today I started to do the same things on a ubuntu machine (with ssh and private key authentication). I've created a ...
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How to build an ethereum based wallet with custom UI?

I have been interested in ethereum for quite some time now and have always wanted to learn ethereum development. I decided to create my custom erc20 tokens i was able to create 2,00,000 tokens. Now i ...
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How to download the blockchain of a single ethereum contract’s address?

The blockchain required to run ethereum is several Terabytes large. This means more than 9 years would be required to download it with my connection speed. In my case, I just want to know if the ...
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Why is PoW needed to confirm transactions and add new blocks [closed]

I have read and I vaguely understand about how Proof of Work works and what does it do. But why PoW? Or more bluntly, why do we need any algorithm at all to add new blocks. What would happen if ...
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Exchange ERC20 token with other ERC20 token

I have 2 ERC20 tokens. The contract are designed as standard ERC20. Here are the 2 tokens to take as an example - AUDC --> Contract Address: (0xContractAUDC) Wallet Address: (...
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Blockchain Development [closed]

I want to build a blockchain network such that if one node updates, all the other linked nodes gets update too. Think of it as Centralized Hospital record in multiple cities, if any of the city pushes ...
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web3.exceptions.BadFunctionCallOutput: Could not decode contract function call getEvidence return data b'' for output_types ['string']

Solidity Code: function getEvidence(string memory _evidenceID) view public returns (string memory) { require(evidenceOwner[_evidenceID] == msg.sender); string memory evidenceHash = ...
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Create2 and new contract deploy at used address

Given that it seems possible, using somehow CREATE2, to deploy a new smart contract at a certain address where a different smart contract existed before to be killed... (see @smarx answer here Can ...
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Can you use a private Ethereum blockchain network to deploy an actual application for the public?

I am starting to do some research for my blockchain based project and I was wondering if it is possible that I can deploy my project on my very own private ethereum network for actual public use and ...
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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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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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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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229 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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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) { ...