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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Conceptual Question About the Fundamentals of Blockchain

there! I am learning from tutorials how to develop smart contracts. I am stuck though not in the development itself, but in the concepts - that I think are not really well explained in the tutorials I ...
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How to create a public Test-net?

I wanted to implement a public testnet on ethereum on python can anyone help me it must be proof of work as consensus method and currently i am learning hashing and how to implement proof of work but ...
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Can I get the hash of any past block using Solidity? [duplicate]

Is there a limit of blocks ago that I can get the hash of within solidity using block.blockhash()?
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How to take input in remix for 2D array in solidity?

My Contract code contract SomeTokenVesting { mapping(address => uint256[6]) public vestingAmounts; constructor() { // some code } function addSomeBeneficiaries(address[] ...
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Cannot read properties of undefined (reading 'address')

Im trying this Solidity and VueJS tutorial from MEDIUM. I even git cloned the github sourcecode, but I keep getting this error on the browser console: ERROR 1: Error initializing Drizzle. ERROR 2: ...
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How to securely decrypt game data inside smart contract

I have a problem I haven't been able to figure out, as follows: Suppose I have a game running on the blockchain (a solidity/smart contract game) where there are a limited number of plots of land that ...
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make your stablecoin decrease in value and pay dividents

is it possible to create a stablecoin and make it decrease in value and pay out dividents on a monthly basis on the ethereum network?
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How to walk down an API when making a chainlink get request?

Am trying to make a chainlink Get>Bool httpget request on the fantasy premierleague API but keep getting a false response. my code is: ''' function getGwstaus() public returns (bytes32 requestId) ...
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Ethereum/blockchain application for historic building preservation

Could I run a potential application of Ethereum past y'all and get your thoughts? I live in a town with a strong sense of community and identity due in part to a number of distinctive historic ...
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Web3js Module Not Found

I'm using latest version of node, latest version of web3js. I'm pretty new to this and trying to test out some web3 stuff. I'm trying to use the getPendingTransactions as mentioned on the web3js ...
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TypeError: Wrong argument count for function call: 0 arguments given but expected 1. token = new ERC20Basic();

When I try to compile the code on Ethereum's own site, I get the following error. Can you help me? line: 99 pragma solidity ^0.6.0; interface IERC20 { function totalSupply() external view ...
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missing ethereum in blockchain.com [closed]

I created my account on blockchain.info in Aug 2017 and my Ethereum Address was assigned 0xf83509a2E197CB3633e732Ba96A679DCe1C6d5B7 I bought 1 ETH on 20/08/2017 and converted my other BTC coins to ETH ...
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Cutting "transaction fee" other than "gas" in an ERC20 token transfer transaction

good day. I'm new to smart contracts and couldn't figure something out. I am using the following contract for ERC20 token transfer. Actually, everything works fine, there are transfers, but what I ...
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How a smart contract persists data and upgrading a smart contract code

I have finished a course on solidity and the blockchain itself and there are some concepts I don't have clear yet. Could anyone confirm these assumptions?: When we deploy a smart contract, its code ...
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How to Index Uniswap Token Price with local Indexer ( with Geth or True Blocks, Chifra)

How can I collect token price data from Uniswap with a local indexer (True Blocks) or Geth? is it even possible without running a node, or a light node? I am new to this and I don't really what to do, ...
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How to a write a subsidies contract?

I am new to solidity and Trying to wrapper my brain around it; I have being Writing this contact but, I am getting an error , cannot able to Store variable in contract. Function of contracts:- _dbs2....
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Google BigQuery Ethereum transactions: transactions_type

In the Google BigQuery transactions table, I was wondering what the values in "transaction_types" stand for - they are either 0, 1 or 2. Many thanks.
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Error: could not import signer account while build the project in golang

hi all I am getting the error while running faucet.go with the command ./build/bin/faucet now I am facing the error:- CRIT [09-15|13:11:25.287] Failed to import faucet signer account err="...
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Referencing common array in multiple mappings

Trying to understand memory in blockchain for sharing reference of array as common storage for multiple mappings. Let's say there is a need for following relationships. So there will be products keep ...
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How can I create a smart contract using another smart contract?

I want to create a smart contract which I can link to my website using web3.js and create input fields for creating a contract using the main contract and I can set the fees also which should go ...
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@ethereumjs/tx - "TypeError: Common is not a constructor"

I was trying to implement a method for signing an eip-1559 transaction using @ethereumjs/tx package. While following the steps mentioned in their documentation , I am encountering an error when trying ...
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does reorg change a order of state update?

if some of my calls to contract update state in order and reorg happen at blockchain does that alters state update order? ex: value = 0; addone() -> value = 1 // reorg happen and this update to ...
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how do u use withdraw function after deployment of smart contract?

I am a newbie here trying to understand smart contract. So when user transacts, money goes to the contract and then how do we call the withdraw function to withdraw the money? Can this done on front ...
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Getting Empty strings back - Ethereum

I am developing E-Voting system and when I enter my Data it works fine but when I retrieve my data it return my empty strings. .Sol File: // SPDX-License-Identifier: MIT pragma solidity ^0.8.7; ...
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How do royalty fees work on the OpenSea and Rarible?

Suppose the creator mints the NFT on the OpenSea platform, but the NFT is later sold on Rarible or some other platform. Creator won't get the royalty fee in this case as per OpenSea documentation. ...
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How is Metamask able to interact with Ethereum if it doesn't require running a full node?

How is Metamask able to interact with Ethereum if it, Metamask, doesn't require running a full node? Does Metamask use any third-party service for it? If so, is this the only way - to use a third-...
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etherscan value to ETH conversion - not wei or token decimal

According to etherscan API, I have 'value': '1302084648252671026' of MVI token. On etherscan.io, I have 0.034063 ETH of MVI. How to I get from the value to ETH? What is value(wei gives me a different ...
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RPC Error: execution reverted

I am Developing EVoting system as my final year project and i am encountering this error RPC Error: execution reverted Voting.sol // SPDX-License-Identifier: MIT pragma solidity ^0.8.7; contract ...
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Why do we need to confirmation blocks?

I am curious about why do we need to confirmation blocks. I mean; all nodes getting a consensus after then add this block to the chain. Right? If all nodes not in a consensus why this block added to ...
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get total transaction value for block

I have written a simply while loop to return the total transaction value of a block, however, it takes almost 30 seconds. Therefore I am looking to the community for a much faster way of retrieving ...
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How should a dapp store & query user profile data?

We are currently working on a dApp that will store user profile data and let its users query them. We haven't been able to figure out how to do that efficiently so far, and therefore we need to ask ...
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Xinfin XDC wallet

I bought some XDC through guarda. I wanted to put it in the XDC (XinFin) wallet. After transferring from to guarda to XDC wallet, I cannot locate my purchase.
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Do I need to front the cost of gas to sell a collection of NFTs

Forgive me if this has been asked before, if it has please provide any resources so I can learn more! I'm having trouble wrapping my head around the development process of creating an NFT.Say I want ...
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Is there any way to store data without fee in solidity

I wonder if there is any way to store data in smart contract which does not charge fees or can we use any external EASY data from smart contract. In my contract I have to update lots of fields on ...
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Where can i found advanced courses about blockchain security?

Where can i found advanced courses and walkthrough box like TryHackMe and HackTheBox, about blockchain security and Defi, ethical hacking with challenges todo to learn about it. Best regards
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ethereum blockchain and off-chain(cloud)

I have 2 questions regarding the DApp data Is it possible to store data on ethereum blockchain and off-chain(cloud) at the same time from DApp? Can we create a link between ethereum and off-chain ...
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How to write Test case for Internal functions in solidity which inherits the ERC721

**This is my Smart Contract code which has inherited the ERC721 and I want to write the test case for _setTokenURI ** contract ProductNFT is ERC721 { constructor () public ERC721(_tokenName,...
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If ethereum is decentralized, then how is it updated?

I regularly read about updates of Ethereum (and other crypto currencies). But if there is no central authority, then how are these updates implemented? Btw I do have programming experience and I know ...
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What's the best way to index the entire ETH blockchain?

I'm trying to get all transaction/token data given an address. Right now I'm using the etherscan API which is fine but makes me dependent on 3rd party software as well as their requests/s limits. Is ...
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Error while Install web3.py. "python setup.py egg_info": Microsoft Visual C++ 14.0 or greater is required

I am trying to install web3.py and get this error: ERROR: Command errored out with exit status 1: command: 'C:\Users\onlyd\AppData\Local\Continuum\anaconda3\python.exe' -c 'import sys, ...
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Deployment of smart contract for research. Infura, Truffle or Metamask (which is more practical)?

Truffle, Infura, Metamask which is more practical way to deploy smart contracts for research purposes? Can someone explain? Thank you.
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About IPFS client add() function

I am digging into ipfs field in order to start a NFT project so that I am working with frontend with ipfs-http-client npm package (npm i ipfs-http-client). My simple test code is like below: const { ...
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Chanlink Public CryptoGraphy

While chainlink creates a random number and more secure public cryptography algorithm, I recently came across the quantum resistive ledger concepts and resistive to a quantum computer with hash mesh ...
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Physical location of Ethereum World State Trie

First of all, allow me to admit to a mistake I made on the other sites like this one, when I asked almost the same question. I feel it is ethical to explain this. I mistakenly asked this question on ...
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1answer
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Smart Contracts developed for Ethereum can also be used in Binance Smart Chain?

I'm newcomer to blockchain and i'm starting to develop a new token, and i've seen many places telling the similarities between the two blockchains. And i read that BSC have a EVM(Ethereum Virtual ...
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How to write test case for the require function

**Contract** contract ProductNFT is ERC721{ uint public totalSupply; address public wadmin; address public brand; address public designer; ...
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publishing blocks with delay

this is rather a simple and fundamental question but nevertheless i couldn't find any solution for it and now I'm worried if it can cause real attacks to slow blockchains. imagine in a form of ...
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Need to Take a Snapshot of all addresses of a tokens on Ethereum network at a given time

So I would like to have a list of all Addresses of a particular Token on Ethereum at a given time in the past. Like a month ago. I am not a Dev, So how do i get a snapshot of the blockchain. Please ...
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how can i fetch a data from file to function using solidity contract?

imagine that I have a list of voters data and I want to send a file to the function addVotersList to add all the voters by one click rather than sending the data one by one for each voter this is the ...
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removed mined transactions consequences

I'm building a game on ethereum and one thing that really makes my life hard is understanding the removed mined transaction flow. what happens to other transactions that counted on that transaction, ...

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