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.

0
votes
1answer
22 views

Where to store data when creating a blockchain based solution?

I have a question regarding the storage of data when creating a Dapp. For example i create a real estate website on ethereum blockchain where people will buy or sell properties on the basis of tokens ...
0
votes
1answer
24 views

Calling a function from another contract is not working. But calling the function from deployed contract is working

I have a problem with calling a function from another contract. I don't know why it is not working. Contract DateTime(https://github.com/pipermerriam/ethereum-datetime) is a util for converting ...
1
vote
3answers
20 views

How can i send data to Contract's function with sendTransaction?

i hava contract like this pragma solidity ^0.5.0; contract Sample { string public name = "sample"; function set(string memory _name) public { name = _name; } function get() ...
0
votes
1answer
38 views

How does Ethereum calculate balance for a new transaction if there are already unconfirmed transactions in the mempool?

Whenever a new transaction is made, it is added to the mempool and a miner will take these transactions from the pool and try to generate a block which contains this transaction. However, before ...
1
vote
1answer
29 views

Static difficulty in 1.8.27 for local network

I am having trouble getting geth 1.8.27 to have a static difficulty on a private network. I followed the instructions from here. But when I test it, the difficulty still increases. I tried again, ...
0
votes
0answers
29 views

How to auto-execute smart contract's function by Aion or other method in the private chain?

I was a little bit confused about Aion scheduling system, because I want to do it on the private chain, in the example https://github.com/ETH-Pantheon/Aion, they have both smart contract Aion and ...
0
votes
1answer
32 views

How to connect with Metamask and Smart contract?

I am ready with my frontend design. I have only 3 files HTML, CSS, and JAVASCRIPT. So, I didn't create any project or DAPP to have other files. Now next step is to connect with metamask and smart ...
1
vote
1answer
87 views

My Solidity files are not compiling and I am getting constant error

I'm new to blockchain and I'm following a tutorial. However, I'm getting problem compiling my first contract on Truffle. Here's my code : pragma solidity ^ 0.5.2; contract ApprovalContract { ...
1
vote
0answers
9 views

I am sending some ether from account[0] to account[1] using geth console. But the amount is not getting added to the receiving account

I tried to mine the transaction using miner.start() command, still account balance remains the same > miner.start(8) I0428 16:27:15.927553 miner/miner.go:136] Starting mining operation (CPU=8 TOT=...
0
votes
0answers
46 views

How can I display the data returned from the solidity function?

Here is a js file that will try to get the list of departments entered into the system. I wanted to display all the department's name in a html page. But nothing is displaying. Below code is the js ...
1
vote
1answer
49 views

Access deployed smart contract using web3.js

I am new to Etherium smart contracts. I have created a smart contract and deployed it on https://kovan.etherscan.io. Now I am trying to access this contract from node js. below is my code but I am not ...
1
vote
0answers
35 views

Parity syncing in archive mode stuck at block 4839206

I am running Parity inside docker in pod in Kubernets on Google Cloud. The pod is using disk with 2700 GB for storing Ethereum blockchain, and currently disk has about 2100 GB free. Unfortunately for ...
0
votes
1answer
23 views

How to show the time when the blockchain contract called? [duplicate]

I want to show the time when blockchain contract called. I am currently saving the time in the blockchain using a method like this function userCheckIn(uint placeid) public { userCount++; ...
0
votes
2answers
74 views

How can the smart contract auto execute the function in the private chain?

I know currently, we can use the Ethereum Alarm Clock and Aion scheduling system to execute the function automatically, but according to what I know, it only can work in Main Net and Test Net(Rposten)....
0
votes
1answer
55 views

ganache-cli: how to persist new created accounts

I start my service by: ganache-cli -d --gasPrice 0 -q --db=./db This persists my 10 defaults created accounts, but when I create new accounts using Web3: web3.eth.personal.newAccount('password') ...
1
vote
1answer
16 views

Can anyone with part of the chain (e.g. a light node) read unencrypted transaction data?

I need clarification on the fact that "the blockchain is public and anyone can read it". Given a node which is storing only, say, 1 block from the blockchain, can that node read the transaction data ...
1
vote
1answer
26 views

Can Qorum Blockchain supports partail transaction encryption?

My use case is that we need to protect sensitive data in the transaction in blockchain. But we want to open other data in the same transaction to the public, Can Quorum support the above mentioned ...
0
votes
1answer
37 views

How to send ERC20 Token?

I try to send Token based on Erc20. and I can send Ether and something function but i dont know how to use transfer function in javascript like that. function transfer(address _to, uint256 _value) ...
1
vote
1answer
22 views

Listen smart contract event

I use parity --light geth --syncmode "light" I would like to listen smart contract Event. Do I need to download all blockchain on local PC or light mode will be enough?
0
votes
0answers
20 views

what is the standard server configuration for hosting own kovan validator node?

What is the recommended hardware specifications ( CPU, RAM, Network ) to host my own validation node for kovan testnet and what is the average data transfer out from validation node?
0
votes
1answer
22 views

Stop Data mining on Private Blockchain running on Etherrum platform

We have setup a private blockchain platform using Ethereum and we are using Java based UI layer for it. Can we stop mining process as it is taking lots of time and making the transactions slow?
1
vote
3answers
150 views

How much does it cost to develop and run dApp on Ethereum or Hyperledger fabric?

When we develop and run a non-decentralized application it causes costs for using cloud server. How much does it cost to develop and run dApp on Ethereum or Hyperledger fabric? Which one is cheaper?
0
votes
1answer
23 views

Does a PoA based permissioned blockchain relies on cryptocurrency as tokens?

I am studying different categories of blockchain. Since the validator nodes are pre defined in the PoA based blockchain, and also mining is not required to determine the next valid block. Is it ...
0
votes
1answer
20 views

Are the terms consensus mechanism and consensus algorithm the same?

I have seen that the terms consensus mechanism and consensus algorithm are used interchangeably sometimes. Are they really the same or there is a subtlety to it?
3
votes
1answer
65 views

When is a new block created?

I am currently reading an interesting book about solidity, and I'm reading about block creation. This gives a good overview: The book mentions that the maximum size of a block is determined by the ...
1
vote
3answers
126 views

Can't compile old solidity contracts(version 0.4.17)

I'm new with blockchain development. I'm working on an old project which use solidity 0.4.17 and truffle ^4.0.0-beta.2; These versions were in the package.json file of the project. When I installed ...
0
votes
0answers
7 views

How are the initial authoritative nodes determined in the PoA consensus protocol?

I am studying the different consensus protocols available. The Proof of Authority model claims to have a set of trusted nodes who are accountable for the validation and verification steps. My ...
1
vote
1answer
27 views

Is mining specific to unpermissioned blockchain?

I was studying the differences between permissioned vs. unpermissioned blockchain and came across this: https://www.youtube.com/watch?v=llCjL1up65M Here it mentions that mining is not required for ...
1
vote
1answer
10 views

How do I list the running nodes with geth?

Is there a way to list the all nodes on my computer with geth command line, and maybe even see some status for them? (I'm new to go-ethereum, apologies if this is a noob question, but I cannot quite ...
1
vote
1answer
15 views

Can I get the timestamp for a transaction added to mempool?

Can I get the time stamp on when a transaction was added to the mempool and when it was successfully added to a block? Is there an API to do this?
0
votes
2answers
45 views

How the “data” field of transaction is saved in the Ethereum blockchain? [closed]

as I imagine there are 2 options: in pseudo language: 1) block.add(tx.data); block.calculate_hash_for_blockchain(); 2) block.add(some_hash_function(tx.data)); block.calculate_hash_for_blockchain(); ...
0
votes
0answers
27 views

Unable to Synchronize raspberry pi node my private network

I have created a private network with 3 nodes - two nodes in computer and one in raspberry pi I connected computer and raspberry pi to same network through LAN computer ip: 192.168.122.1 pi ip ...
0
votes
1answer
37 views

Network propagation delay and forks in Proof of Stake?

I am learning the fundamental of Proof of Stake (PoS), i came accross a question which i could not find answer to. Assume we have three validators (aka miners in PoW), V1, V2 and V3. Each of the ...
0
votes
0answers
68 views

Getting an VM Exception while processing transaction: revert

Post trying to initialize a task using the initTask function, I keep getting a revert exception. I've tried to remove the condition (msg.value >= _rewardUnit*_rewardNum) from the function and ...
0
votes
1answer
25 views

how to generate multiple ethereum addres using Hd wallet?

const mnemonic= 'clown shiver beach wheel this mixture emotion illness fatigue amateur talent bitter' console.log(0x${hdwallet.derive(m/44'/60'/0'/0/0).getAddress().toString('hex')}) const seed = ...
0
votes
0answers
20 views

Send Data into BlockChain Network using w3?

HI I want to store my bank information on ethereum network using w3. can anyone help me to send my data //Bank.sol pragma solidity >=0.4.21 <0.6.0; contract Bank { struct User {...
0
votes
1answer
101 views

ethereumjs-wallet/hdkey is no more in npm

how to generate multiple addresses from single mnemonic? var hdkey = require("ethereumjs-wallet/hdkey") var bip39 = require("bip39"); // You can generate a mnemonic seed with bip39 library var ...
0
votes
1answer
24 views

how can a signature for a document on a blockchain be revoked?

I am trying to do document verification through blockchain. The way I'm trying to do this is by digitally signing a document, and storing its hash on the blockchain. Now I'm trying to create a feature ...
3
votes
1answer
309 views

Infinite loop in a view

How is ethereum network protected against infinite loops in views? In normal transaction you have to pay a gass, so it would be too expensive for you, but calls to views are for free. For example ...
0
votes
1answer
24 views

Import and polymorphism is one contract or more?

If I have this contract: contract HelloWorld{ ... } and this one import "./HelloWorld.sol"; contract HelloUniverse is HelloWorld{ ... } and I deploy it, will it create 2 different contract and 2 ...
0
votes
1answer
9 views

Adding Recent EIP's to Custom Blockchain

I have a custom blockchain running on Parity 2.3.8. My question is do the recent EIP additions (https://coinswitch.co/news/ethereum-hard-fork-jan-19-know-everything-about-3-upcoming-eth-hard-forks) ...
0
votes
0answers
19 views

Error while connecting from Remix via rpc to local blockchain

geth --datadir ./accnt1 --port 30306 --networkid 2018 --rpc --rpcport 8545 --rpccorsdomain=”*” --nodiscover --rpcapi “db,personal,eth,net,web3,debug” --rpcaddr="127.0.0.1" --rpcport 8545 console ...
1
vote
1answer
37 views

what is the role of merkle tree in ethereum? [duplicate]

I know the functionality of merkle tree, it makes a root hash from a group of data.My question is how merkle tree is act in ethereum blockchain,precisesly in the place of transaction hash,block hash,...
6
votes
1answer
1k views

My friend sent me a screenshot of a transaction hash, but when I search for it I find divergent data. What happened?

This is the transaction hash: 0x90e923ee01d9dfeb95ee176819eeec67d247fc6cb009c8cdc4d8ae1939e5ecc6 And this is the screenshot my friend sent me: If you check the hash in Etherscan, some informations ...
1
vote
1answer
147 views

could not be able to change my setmessage because (Transaction has been reverted by the EVM:

I am working on react. As I have deployed my contract onto a specific address which have a following code: pragma solidity ^0.4.17; contract Lottery{ address public manager; address[] ...
1
vote
1answer
35 views

Is there a smart contract recording all block hashes on in the ethereum blockchain, as they come in?

I'm wondering whether anyone has already made a contract and corresponding off-chain service which, once every 30 minutes or so, triggers the contract to record all the block hashes which have gone by ...
1
vote
1answer
23 views

I am trying to build a land registry of land titles on the blockchain, [closed]

Good Day. I am trying to build a land registry of land titles on the blockchain, with the intention of being able to sell such title to someone else. Therefore, the title eventually has to be ...
0
votes
0answers
52 views

Smart contract migration through Proxy delegate pattern in solidity 0.5

I am trying to do smart contract migration in solidity 0.5 using the proxy delegate pattern. When I write the integration test in javascript how should i make a delegate call using the proxy contract ...
0
votes
1answer
15 views

How to get parameters of an object from array using loop

I am using a loop to retrieve an object from array. Then get its details and compare it with other string. But it gives error Type bytes32 is not implicitly convertible to expected type struct ...
0
votes
2answers
40 views

Encryption and Decryption when transmitting data

If I was sending data to a smart contract, do I need to encrypt it before transmitting and decrypt it in the smart contract? Or is this done automatically?