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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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Total number of state entries

I am syncing my ethereum blockchain using the default syncmode. I want to know how many total state entries are there because currently the highest block is 6544578 and the number of pulled states i.e....
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not able to test smart contract

I am getting this error when testing my smart contract. sometimes I am getting this error and sometimes its working fine "before all" hook: prepare suite: Uncaught Error: VM Exception while ...
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1answer
13 views

Is it available to have an application that is managed by single Entity?

If For example Entity A wants to build a smart contract that manage a group of devices. But since each device uses pseudonym and he may change it later, is there any way to build the contract such ...
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Not able to Get the response from the function call from Node Js Service Using Web3@1.0.0-beta.36

I am deploying two contracts A and B using Web3(1.0) and solc. My Solidity file looks something like this: pragma solidity ^0.4.21; contract A { uint public value; constructor(uint newValue) ...
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24 views

Blockchain Transaction similarities [duplicate]

I have a theoretical question about blockchain transactions. Imran Bashir describes a blockchain transaction as a transfer of value from one address to another. Futhermore in Bitcoin you have ...
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1answer
39 views

Get time when the transaction was included in your node

Is there any way to obtain the time when you have received a transaction? I would like to know when is a Smart contract included in my node. (local testnet)
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How to develop my own Api for blockchain [closed]

I want to build my own api to interact with blockchain. Let suppose for ethereum. Kindly guide me hoe can i develop my own api. If there's any document or blog about this, do share the link.
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1answer
20 views

Ethereum propagation delay

I have a very beginner level question. Suppose I have a list containing the IP address of different machines and I want to share them via ethereum blockchain and suppose that the list is very large as ...
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1answer
22 views

How can I get the records of invalid blocks once have been mined?

As we all know, an invalid block will be ignored and won't be propagated when a verifier finds its invalidity. However, if there is a need to get the records of all invalid blocks once have been mined ...
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1answer
23 views

Quorum 7nodes example unable to attach to geth node 1,2,4,5,6,7 but node 3 is working

Quorum 7nodes example all of sudden gave fatal error unable to attach to remote geth. Problem: can't attach to geth node Every time I import metamask account to geth node (using personal.importRawKey(...
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2answers
19 views

Proper way to design a descentralized game

Let's say I'm designing a multiplayer game, where players can fight each other in different battles. As a result of each battle, players get a punctuation. Suppose I'm using a sidechain. Which should ...
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25 views

IPFS. Add a directory recursively with an HTTP api

Is there an HTTP api equivalent of doing: ipfs add -r resources/public where resources/public is a directory with a static website (index.html in the root, css, js etc). Doing: curl -F file=...
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1answer
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Can we transfer ethers using a EOS smart contract

Suppose we want to transfer ether from our EOS smart contract. I know atomic swaps is not possible between ether and EOS blockchain, may be in the future but not now. Is there any other ways round to ...
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1answer
20 views

Ethereum gas limit issue while sending transaction from web3 client (private network)

I have setup a private Ethereum system using geth. And am running a client that uses a web3.js file to connect to the Ethereum system. While trying to send a transaction or call some contract function,...
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1answer
18 views

Should I use Node.js server along with ethereum smart contracts to make Dapps?

I want to make a Dapp using ethereum. So, should I use a Node.js server and a database to store some user's data and store rest of the data on the smart contract that needs to be decentralized or ...
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ERROR[10-06|12:16:29.143] Section processing failed

I am to sync ethereum blockchain on Ubuntu 18.04, 64 bit using command **geth --datadir "/home/maham/Ethereum/EthereumMainNet" --cache 6144** After nearly 11 hours of syncing it stopped with the ...
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Is there a way to get back our lost/hacked/forgotten private key? [duplicate]

Now a days,if I am not wrong, everything is being clubbed with the private key and it is the user's responsibility to protect and securely keep his/her private key? So what if the user loses/forgets ...
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What are some fullnode health indicators in geth? (mgasps etc.)

I run a few ETH fullnodes using the Geth implementation, and I'm curious about some of the metrics, specifically mgas, mgasps and how they reflect the health state of the node. Here is the output of ...
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2answers
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How can I store and read data from Etherum blockchain? [closed]

I'm doing a project and I want to store some basic information on Etherum, for example: Name, ID, Height, Weight. How can I store this on the blockchain and after that be availble to read it. I read ...
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1answer
26 views

Retrieving transaction hash in all blocks after fast sync

I have set up an ethereum node using fast syncmode. I want to retrieve all the transaction hashes and the recipient between a range of blocks, let's say 0 - 13000. Will I be able to retrieve the ...
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3answers
107 views

Maximum known Ethereum fork length

What is the maximum known Ethereum fork length? What is the maximum Ethereum fork length in theory? Edit: please read fork length as maximum number of uncle blocks.
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1answer
20 views

Metamask transaction pending? [closed]

Transaction send through metamask with all parameter correct is not included in block in private network.
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3answers
59 views

What are the main differences between blockchains & distributed ledger technology from a technical perspective?

Is there any solid justification that every blockchain is a distributed ledger, but not every distributed ledger is a blockchain?. What are the main differences between blockchains & distributed ...
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intrinsic gas too low on contract deployment

My question is about the intrinsic gas too low error when deploying a contract I've calculated the gasprice with: https://www.ethgasstation.info/calculatorTxV.php and my gaslimit is 5 milion. Could ...
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2answers
29 views

Get contract information from transaction information?

This might be a simple question. Let's say I have the transaction hash: { blockNumber: "6214286", timeStamp: "1535248365", hash: "...
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2answers
31 views

how to reach consensus berween only 2 peers?

Can consensus take place between only 2 peers? Scenario: I am a patient who is visiting a doctor and all the communication/transaction between the both of us happen via a blockchain based app. So ...
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0answers
29 views

Factom vs. Ethereum blockchain

I'm very familiar working with ehthereum blockchain including writing smart contract, setting up nodes and writing decentralized applications. Is it correct to say that you can do all of it with ...
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1answer
20 views

How to read previous blocks data?

I'm new to block chain technology. I'm trying to store and read blocks using testRPC along web3.js. I'm able to get the latest block data but not able to fetch previous blocks data. Please some one ...
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0answers
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Why is my private ethereum network stuck at “Recalculated downloader QoS values” while trying to mine?

I'm using Mac OS High Sierra version 10.13.6 My customgenesis.json file is this. {"config": { "chainId": 15, "homesteadBlock": 0, "eip155Block": 0, "eip158Block": 0 },"nonce": "0x0000000000000042","...
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4answers
811 views

Why are contracts in Ethereum Blockchain called as 'Smart Contracts'?

We write smart contracts in ethereum blockchain. How did contracts get its name as Smart Contracts? Why are they called as Smart Contracts?
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3answers
54 views

Reading from the Ethereum Blockchain [closed]

I came across this statement online in one of the articles "In order to read, you need to verify the chain". I am not able to comprehend this statement. Does that mean I should always run a node to ...
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1answer
24 views

Error while running web3 instance

I have a 2 node Ethereum system already setup. I am trying to have a web3 client talking to it. I installed web3 on a client machine and it gave no errors. However, I try to setup index.js and do ...
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0answers
32 views

ReferenceError: beforeEach is not defined

my question is about run a js file from cmd and node i have a js code like this : const assert = require('assert'); const ganache = require('ganache-cli'); const Web3 = require('web3'); ...
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2answers
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ethereum smart contract security check [closed]

How to prevent smart contract from the vulnerabilities? what are all the security measurements we need to consider before publishing our smart contract? Regards Mani
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1answer
27 views

How calldata is stored in memory?

when I execute this: bytes8 h = 0x000008dfe2f440000733c; t.call.gas(0x7e0b0)(bytes4(keccak256("enter(bytes8)")),0x8dfe2f440000733c0000000,h); the calldata is : 0: ...
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1answer
51 views

what are the diffrences between <address>.call and <address>.<function name>?

contract GatekeeperOne { address public entrant; modifier gateOne() { require(msg.sender != tx.origin); _; } modifier gateTwo() { require(msg.gas % 8191 == 0); _; } ...
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1answer
22 views

basic ethereum setup help

what I want to do: 1. Install ethereum on multiple nodes in a network. I have some Linux machines for this purpose already. 2. I want to have a client (let's call it myApp.exe). myApp.exe gets user ...
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2answers
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Is there a block property that is determined after the block is published?

I wanted to know if is there a block property in ethereum that (is not determined) no one knows (even the miner of that block) before publishing it to the network?
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miner.start(1) triggers but not starting the mining

I am creating my own private ethereum blockchain. sudo geth --rpcapi eth,web3,personal --rpc --networkid=15 Above command gives the below logs. INFO [09-18|10:16:42.151] Maximum peer count ...
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1answer
35 views

GETH Error on personal_sendTransaction/eth_sendTransaction

Been trying to use personal_sendTransaction / eth_sendTransaction for days but I cannot get pass this error. I have tried different combination of gas/gasprice/value but I cannot make it work. PS. ...
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1answer
39 views

mint method usage in ERC721 token implementation

What does the internal method call _mint(msg.sender, tokenId) really do in the background when used with ERC721 token implementation?
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1answer
8 views

how do I make users sign different strings with their private key separatelly

Here is the the scenario. Users come to my website and register(by using email and password). Then they login. After that, They add a new item(which has name and quantity fields). After Clicking ...
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0answers
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how to get public key from metamask? [duplicate]

I'm creating a dapp. and I need my users on my website to provide public keys. As I am lazy to write a script which generates public/private keys automatically, I want to suggest an idea that they use ...
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0answers
24 views

Launch same Dapp from different nodes in a local tesnet

I have two nodes running on my computer, creating a local testnet. When I deploy a contract through truffle, I add into the truffle.js one of the ports of one of the nodes, from where I want to deploy ...
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2answers
27 views

Block archived event inside blockchain

I want to write a gambling smart contract, that will be based on time (on block number in the ethereum blockchain). What is the best way to do some work when current network block will archive some ...
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1answer
17 views

Transaction successful but ether not transferred to destination account

I am following this article and everything works expected but ether is not getting transferred to the to account.Please find the logs below. eth.sendTransaction({from:eth.accounts[0], to:eth.accounts[...
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4answers
41 views

how does myether wallet works (website)

I want to create a website where my users can register and login but not using any kind of database. I want to use public/private key. Let's take https://www.myetherwallet.com/. It says that It doesn'...
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0answers
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web3-eth-accounts.js is not installed

I have seen plenty of questions related to that but I cannot find a concrete solution. I am trying to build this lib but I always get errors when I try to build it, so I cannot get the dist/web3-eth-...
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0answers
34 views

Implement blockchain into our reward system

Our company(e-commerce) is planning to integrate blockchain technology into our loyalty program. However, I am still doing research on how to make this work as we don't have tech. guys that can build ...
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1answer
31 views

Problem creating my own wallet with multiple accounts

I have a local blockchain where I have deployed a contract. I want to interact with it sending multiple responses at the same time. For this propose, I cannot use Metamask to confirm each transaction. ...