Questions tagged [blockchain]

A blockchain is an open, distributed ledger that can record transactions between two parties in a verifiable and permanent way. The ledger itself can also be programmed to trigger transactions automatically.

A blockchain – originally block chain – is a distributed ledger that is used to maintain a continuously growing list of records, called blocks. Each block contains a timestamp and a link to a previous block. A blockchain is typically managed by a peer-to-peer network collectively adhering to a protocol for validating new blocks. By design, blockchains are inherently resistant to modification of the data. Once recorded, the data in any given block cannot be altered retroactively without the alteration of all subsequent blocks and the collusion of the network. Functionally, a blockchain can serve as "an open, distributed ledger that can record transactions between two parties in a verifiable and permanent way." The ledger itself can also be programmed to trigger transactions automatically.

Blockchains are secure by design and are an example of a distributed computing system with high Byzantine fault tolerance. Decentralized consensus can therefore be achieved with a blockchain. This makes blockchains potentially suitable for the recording of events, medical records, and other records management activities, identity management, transaction processing, and documenting provenance.

Definition taken from Wikipedia - Blockchain

One of the most well-known use-cases is cryptocurrencies, but can be used for distributed agreement on other things.

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Metamask automation with Selenium webdriver

I'm trying to get to a Dapp that needs Metamask extension to access it. I added it through chrome extension. I know how to add the extension to the chrome instance in selenium but I don't know how to add a password etc..Could anyone download…
gabe
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How to send an ERC20 token with web3js

I'm currently using the 0.2x.x version of the Web3 JavaScript API. I deployed my custom ERC20 token by creating smart contract in solidity (on REMIX IDE). I installed the MetaMask and had a test on https://wallet.ethereum.org/ to send some custom…
rachel_hong
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How to extract all used hash160 addresses from Bitcoin blockchain

I have all 150GB Bitcoin blocks now what? How to open them and read them in Python? I need to extract all used hash160 so far I tried to open them with Berkeley DB but no success it seems these files aren't Berkeley DB and what is the difference…
John Kotkin
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Ethereum Solidity - Does require() use any gas?

Google has failed to give me an concrete answer, does using the require() function in Solidity use up any gas? Even if the statement in the function is evaluated as true?
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How does "Coffee with Blockchain" match growers to buyers?

In the "Coffee with Blockchain" app produced by IBM it performs price matching between Growers and Buyers. I'm wondering how that matching would be implemented (either in the example app or in an actual implementation). Example of the app can be…
Rob Olmos
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Is there any way to initiate a disconnect request to the Metamask wallet?

I'm building a decentralized application where users can connect their cryptocurrency wallet (Metamask) to my website. They can initiate a connection request by clicking a button. On success, the wallet is connected and my website can interact with…
vladwho
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How to watch for the bitcoin transactions over blockchain via nodejs?

I am using this bitcore npm package. https://bitcore.io/api/lib And i want to monitor all the transactions over the blockchain, and read the input address, output address and amount associated with that transaction. But i am unable to find the…
codeofnode
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ERROR: manifest for hyperledger/fabric-orderer:latest not found

I am trying to start up network using following command ./network_setup.sh up channel After running this command I am receiving this errro ERROR: manifest for hyperledger/fabric-orderer:latest not found How I can remove this error?please help me
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Error: The method eth_sendTransaction does not exist/is not available

Showing an error while calling solidity contract, which is deployed already in ropsten-infura. I'm using web3(@0.19.1) for calling contract. Anybody faced the same issue?
Aditya V
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Is blockchain a decentralised database?

I understand bitcoin uses blockchain technology to maintain a decentralised ledger of all transactions. I have also read many posts eluding to future applications of blockchain technology, none of which have been very clear to me. Is blockchain…
Dercni
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Are blocks mined in HyperLedger Fabric?

I have been reading the documentation on how HyperLedger Fabric's project is implementing a open source BlockChain solution: https://github.com/hyperledger/fabric/blob/master/docs/protocol-spec.md I have seen that PBFT consensus algorithm is used,…
Marc Cayuela
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`Property 'ethereum' does not exist on type 'Window & typeof globalThis'` error in React

I am getting the Property 'ethereum' does not exist on type 'Window & typeof globalThis' error in React. This is the line generating the issue: import { ethers } from 'ethers' const provider = new…
Boris
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Error HH604: Error running JSON-RPC server: error:0308010C:digital envelope routines::unsupported

I am setting up hardhat in Linux. I have set up the react app first using these commands. npx create-react-app react-dapp cd react-dapp Then I have installed some hardhat dependencies using this command. npm install ethers hardhat…
enstazao
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how to sign bitcoin psbt with ledger?

I'm trying to sign a Psbt transaction from bitcoinjs-lib following what I found here: https://github.com/helperbit/helperbit-wallet/blob/master/app/components/dashboard.wallet/bitcoin.service/ledger.ts I've checked that the compressed publicKey…
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Hyperledger Fabric GOSSIP_BOOTSTRAP & GOSSIP_EXTERNALENDPOINTS

I was looking into the docker configuration files and found two parameters in peer environment as shown below: environment: - CORE_PEER_ID=peer0.org1.example.com - CORE_PEER_ADDRESS=peer0.org1.example.com:7051 -…
Akshay Sood
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