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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Deploy dapp on private blockchain network

i have create a private network with 2 nodes. I have connect an account with metamask from my private network and i have created a full dapp ( contract,front-end). Now i want to deploy the whole dapp ...
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7 views

Do i need to create Checksum in blockchain? [on hold]

I'm trying to develop blockchain application, since it is newly developed do i need to create my own checksum algorithm ?
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26 views

Error while importing Libp2p package in blockchain

I have installed some js-libp2p's packages on my Ethereum Blockchain-ipfs project and I wrote some codes like below. const TCP = require('libp2p-tcp'); const MulticastDNS = require('libp2p-mdns'); ...
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20 views

Time in blockchain and HTML

I'm trying to get time once data is submitted off-chain, since only way to get on-chain is via now to get the block time. Off-chain I'm using "document.getElementById("demo").innerHTML = Date()" to ...
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1answer
14 views

No web3.min.js while download Zip file from Github

I am following a youtube tutorial to make a simple dApp. In this tutorial he is telling to get Web3 from GitHub. I downloaded the Zip of Web3 from the GitHub and i get following folders and file after ...
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16 views

How to compile solidity code in Kali Linux

I have tried to install the remix IDE for compile my codes in solidity, since for some reason the remix IDE don't open online. I executed the codes bellow and give that errors. Sorry anything ...
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13 views

Can't call contract function in Remix in Web3 provider mode, but it works in Javascript VM

A simple contract for addition, an error is reported when calling the function add in Web3 provider mode: "Gas estimation errored with the following message (see below). The transaction execution ...
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30 views

Why this error occurring when i running my dapp?

I create a dapp using Solidity,Web3Js,Javascript and Html with metamask i always getting this error when i am trying to submit my transition i am getting this error at c (inpage.js:1) at ...
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41 views

Solidity Error Address / Address Payable

I'm currently learning solidity programming to create a basic smart contract based on a 2018 tutorial where solidity was using version 4. I'm currently using truffle v5.0.21. I understand that there ...
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13 views

Problem connecting web3 via websocket to node with nginx

we are trying to connect to a geth node via WebSockets to be able to subscribe to contract events. This node is created with docker and this docker uses nginx as a proxy. We can connect easily with ...
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27 views

Solidity: TypeError: Member “unbond” not unique after argument-dependent lookup in contract super EthGatedMarket

I'm getting this error: TypeError: Member "unbond" not unique after argument-dependent lookup in contract super EthGatedMarket. super.unbond(msg.sender, gatewaySpecifier, quantity); ^----------...
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204 views

Offchain vs Sidechain vs StateChannel

What are the main differences between off-chain, sidechain and state channel? And what are the use-cases of all of these?
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21 views

how? blockchain fund transfer error .. missing funds [closed]

How is this possible on the blockchain? Sent 275.80 ether from Binance, transfer confirmed, to another exchange, block chain confirmed. Funds deposited were 0.04 ether, not 275.80 !! This was 3 weeks ...
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43 views

Three questions

I have recently become interested in crypto and after much reading on Ethereum I still have three burning questions that perhaps some of you can help with. Apologies in advance as some of these might ...
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33 views

Error: The data field must be HEX encoded data

I am trying to make a simple dApp by using a tutorial. I am using the following command ; npm install ganache-cli web3 so that we can use web3 to get fake ethereum nodes/accounts by connecting it ...
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42 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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8 views

How can I combine Quorum and Zero Knowledge Range Proofs

How can I combine Quorum and Zero Knowledge Range Proofs I have 20 years of experience at java JEE coding, and 10 years in devops as well, but no experience with blockchains, or the Go language. I ...
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7 views

What repo in loom do I fork to create my own sidechain?

I am trying to create a sidechain. I believe I need the code for the node that supports the sidechain. How many repos will I need to collect to properly start my own sidechain? Ideally a proof of ...
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12 views

Could the parity-ethereum client incorporate doing range proofs in the ethereum blockchain?

I want to be able to prove that I have stored a number that is in the range of a minimum and maximum value, (a range proof) without revealing the number, and put the value into the ethereum blockchain,...
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23 views

How to get the value from the frontend form and save value to the blockchain using +web3 1.0.0-beta.37 + reactjs

I am writing my first Dapp and want to save the value of the form to the blockchain. I am Using React and web3 js 1.0.0-beta.37 on the frontend. Also I am new to react. Following is my App.js ...
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2answers
41 views

How blocks in a blockchain are identified that store concerned policy?

I am working on blockchain. My project is to store Role based access control policies(user-role assignment and role-permission assignment) in blockchain. Policies are written in 2 dimensional array (...
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1answer
16 views

What does it mean that Solidity can encode arbitrary state transition functions?

From Ethereum White Paper: "What Ethereum intends to provide is a blockchain with a built-in fully fledged Turing-complete programming language that can be used to create "contracts" that can ...
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1answer
30 views

plug our own consensus in any one of ethereum client? [duplicate]

Actually i try to add new consensus and will through modifying some consensus to see its effect on transaction throughput. so what platform should i use that provide me this facility or should i use ...
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1answer
28 views

What is the difference between create and newAccount in web3js?

There are two ways to create account one is web3.eth.accounts.create() and web3.eth.personal.newAccount(); function, When I use newAccount() function account is created in my local geth client but ...
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24 views

How to handle password for unlock Account in web3?

In web3 there is function web3.eth.personal.unlockAccount(address [, callback]) to unlock the account so whenever we call the smart contract function we need to unlock the account in geth client ...
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19 views

Where I can find the response in the blockchain (transaction inputs) or storage file in smart contract (resultat of transaction)?

when a user sends a tarnsaction to define the access control of a resource to a device s1,then it will be executed by smart contract and the result of the transaction is stored in the storage file of ...
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34 views

How to know if the token is ERC20 or ERC233?

as I stated on the title because I am very confuse on how to know if the token is ERC20 or ERC233. I bought Thore Cash on Mercatox and I didnt know if it is ERC20 or ERC233 but they said they ...
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2answers
38 views

How the blockchain accepts this smart contract?

When an agent deploy a smart contract, how blockchain accepts this smart contract and sends an address of smart contract to agent. 1-How the blockchain accepts this smart contract? 2-who accepts the ...
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13 views

Want to understand token migration

Can anyone please explain the process of Token migration from one network to another network, Like omesi go and tron has done. they first lauch there own ERC20 token over ethereum and later migrated ...
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1answer
21 views

What is deployed smart contract address in solidity?

In remix IDE when we deployed the contract there is address on it. What is that address and what that address is used for? Like Ethereum account address is use for transaction and identify the user ...
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1answer
24 views

Getting the transaction hash on function call

I am new to Solidity, Web3, and Ethereum. I am trying to build a web application through which users can upload a file to IPFS, then store the IPFS hash in the blockchain. I am using the React truffle ...
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1answer
30 views

Does nonce same for all node?

Suppose in blockchain network we have 5 nodes and we have new transaction done by first node of network, so now rest of 4 node will mine the transaction to commit it in blockchain network, will the ...
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19 views

How merkle tree is used to verify transaction in blockchain

May any one give example how merkle tree is used in blockchain to verify the transaction? I confused because validation of data in ethereum is done through the proof of work where you find the nonce(...
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3answers
43 views

How data is secured on ethereum network?

Blockchain is distributed decentralized database and same data is present on every node on network so now anybody on the network can see my data, so how it is secured over blockchain network?
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19 views

How to prepare for blockchain interview?

I am learning blockchain and want to pursue my career on blockchain, so what will be the best way to do that? What certification I must do and what think I should cover? appreciate all your career ...
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1answer
28 views

What is difference between geth, myEtherWallet and etherscan

I am new to blockchain technology and learning it, there are many terms of blockchain which confused me like geth client, meta mask, etherscan and myEtherWaller. I used geth it's a ethereum client to ...
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1answer
33 views

How to pass a document as function argument(upload document)

I am working on a project in solidity where I want to generate a SHA256 hash value for the document. So which means when I pass a file to a function the function should return the hash value. can ...
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12 views

Parity synced at not existing block 4839212

I have problem with parity, cant get synchronization in archive mode to end, anything, changing arguments, max-, min-, snapshot-peers, parity verisions do not help. I have blockchain in archive mode ...
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1answer
24 views

Automating user data storage on a blockchain

I have a smart contract that contains a function to store data onto the blockchain. The function stores two integer variables to the blockchain. Now, I can manually store the values from the remix-ide ...
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1answer
29 views

How to open metamask erc20 transfer window using web3 apis?

In my frontend I have 'withdraw' and 'deposit' buttons. I want to display the metamask screen that comes after clicking on the deposit and send buttons (of metamask) when the user clicks on the ...
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1answer
11 views

If i pay some service on certain dapp, does this tx can be reverted because of confirmation?

I paid and got service from dapp. does dapp wait until enough confirmation is settled? or not, is it possible that tx can be reverted?
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24 views

where is data store in blockchain? [duplicate]

for example we have contract like this: contract Sample { string public name = "Moore ath John Yuur Gha"; function set(string memory _name) public { name = _name; } ...
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1answer
14 views

How smart contract execute when receiving two transaction in the same time?

When a smart contract receives two transaction by different users, what is the transaction that the smart contract will deal at first ?
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1answer
22 views

How does Ethereum ensure that “users can own their data, and your apps don’t spy and steal from you”? [closed]

What features in ehtereum would ensure that the Dapp would never spy on you or steal your data?
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1answer
13 views

When is chain data (length) compared between nodes? Is there any way to control this?

I am trying to use an ethereum blockchain in a multiagent network. I would like to control when information is exchanged between nodes to keep the network synchronous, so I am trying to figure out how ...
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2answers
17 views

Decrease the time between new blocks in Ethereum Development

I'm trying to create a DAPP (with docker-compose) which will require many transactions, and I am currently experiencing nonce problems with my Transaction Manager. However, I'm not looking for help ...
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19 views

How can I store the hash of a set of data in the ethereum and make the chain validated always?

I am working on a University Management System and I want to develop the system using Centralized Database like Mysql and to keep the data safe I want to use blockchain to store the hash of the data ...
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1answer
56 views

how execute smart contract step by step?

I have a few problems understanding the step of execution of transaction in smart contract. 1-When a user send a transaction to smart contract, this smart contract is not executed immediately instead ...
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53 views

How to decode SHA256 hash value and retrieve data in Solidity

I am working on a project in solidity where i am encode a string to SHA256 hash value, and now i want to decode SHA256 hash value and retrieve the actual data. please help hoe to do it. Below is the ...
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33 views

Store data on ethereum blockchain from a text file

I have a simple smart contract running over a local Ethereum node. It has two functions: one for sending data and another for retrieving it back. I have a text file and want to send data from it to ...