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.

385 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
1
vote
0answers
201 views

Can't open ethereum wallet when blockchain is on my SSD

After a lot of searching I found how to set the datadir path to download the blockchain on my SSD instead of my :C/ drive since that's almost full and now that it's downloading the blockchain i would ...
1
vote
1answer
129 views

iOS node not syncing with private BKC

I use the Geth framework and Swift 4 to boot a node inside an iOS 11.0 app. This node connects to my local BKC (to 4 nodes to be precise). Here are some tests I made : if I start 3 computer nodes ...
1
vote
0answers
99 views

Setting balance to an account

After i created a wallet for a user i want to modify his balance, how could i do that without setting the account address' balance in the genesis, I'm using quorum blockchain with web3j. Thank you!
1
vote
1answer
65 views

liaison entre web3 et nodejs [using web3js and nodjs]

Bonjour, j'ai développé une app avec nodejs et je voulais la transférer vers une dapp en intégrant le web3 librairie. En effet j'ai crée les smart contract il le me reste juste la façon de faire la ...
1
vote
0answers
115 views

How to test forked block on local machine?

Read this article How can I reliably induce a blockchain fork for testing purposes?. Example from that thread is outdated, and need to be refreshed. First my step is create initial chaindata from ...
1
vote
0answers
26 views

Use-Case: building a small test-network, did I got it right?

I've to implement a simple use case and I'm not really sure if I understood everything correctly. What I'm trying to do is to build up a network with a few Raspberry-Pi's, running as full-nodes. ...
1
vote
0answers
179 views

How to configure Azure STRATO Blockchain LTS with Visual Studio?

I'm learning all about Blockchain but I wanted to make an example of smart contract, i followed this tutorial, but I can't find much about how to integrate Azure Strato Blockchain with my application ...
1
vote
0answers
217 views

Ethereum raw data files folder

Where is the folder on Mac OSX where Ethereum put raw blockchain data? I find only *.ldb files, but as I understand it is only the index of full database. For example, in Bitcoin there is blk*.dat ...
1
vote
2answers
354 views

Smart Contract - Update implementation using a Relay with delegateCall

I know that smart contracts are supposed to be immutable and that's the whole point, but to expect someone to implement a logic that never changes (no upgrade or no bugs) from day 1 is also ...
1
vote
0answers
246 views

Parity scheduled transaction stuck at submitting

I scheduled a transaction for the BAT token after block 3798640. It remained pending before the block for hours, then submitted about an hour ago, see Tx local viewer screenshot. Anyone know if this ...
1
vote
0answers
245 views

Is there any benchmark about the speed of blocks search engines?

I want to know the performance of search engines such as blockchain.info, smartbit or blockr.io I know that they are very speed but I want a real benchmark that gives the actual speed (in seconds or ...
1
vote
0answers
105 views

What is a sealer and what is the difference between Ethhash, NoProof and BasicAuthority sealers?

Default sealer in cpp-ethereum is NoProof: https://github.com/ethereum/cpp-ethereum/blob/43bae2c78e2a968ef4eb37bec2da4d9b85fa2392/libethcore/ChainOperationParams.h#L73 But I don't understand what is ...
1
vote
0answers
201 views

Ethereum usage for financial transaction

I am new to ethereum blockchain, and i have following scenario of simple money exchange to be implemented: Consider three account Sender(USD), Receiver(EURO) and Provider. Where provider is account ...
1
vote
0answers
276 views

private Ethereum Network Uncle Mining: blockchain forked from a node even that node still connected to the network

I have a private Ethereum Network. It was working without any problems when I had a single miner. But when number of miners increase, I am faced with the following problem: The way I have started my ...
1
vote
0answers
727 views

How to continue to watch the `Events` from the point `geth` was closed?

I have a private Ethereum network. The bootnode(main node)'s goal is to watch Events and if a new Event is generated than trigger a contract's function that I want to run. The key point is triggered ...
1
vote
0answers
1k views

Is my address valid?

I'm using Blockcypher's API (https://dev.blockcypher.com/eth/#generate-address-endpoint )to generate Ethereum addresses. One such address that has been generated is :- Public Address (...
1
vote
0answers
57 views

What do the progress bars on the Alethzero “blockchain download” window mean?

I'm exploring Alethzero. What do the progress bars in the "blockchain download" window mean? I'm seeing this: I'm assuming this relates to the progress in dowloading the blockchain but I can't work ...
1
vote
0answers
269 views

How is transaction finality correlated with transacted amount?

It was argued by Vitalik Buterin that transaction security can be a function of the amount the transaction carries. This is because of the economics of attacks. How many block confirmations would you ...
1
vote
1answer
157 views

Can someone download and run a local version of my contract?

Say I have a smart contract the preforms a specific function and is used in a decryption process off-chain. Would it be possible for Molly to download the entire contract and run it on their own local ...
1
vote
1answer
614 views

problem when deploy smart contract in Quorum using web3j

I'm using web3J when i try to deploy contract i get Error processing transaction request: Non-200 status code: &{Status:400 Bad Request StatusCode:400 Proto:HTTP/1.1 ProtoMajor:1 ProtoMinor:1 ...
0
votes
1answer
19 views

Error: Returned error: gas required exceeds allowance (89459648255865) or always failing transaction

I am running a contract on a private network in geth, and using web3js. I have the following error when I run a transaction: web3.min.js:1 Uncaught (in promise) Error: Returned error: gas required ...
0
votes
0answers
11 views

Connect to any ethereum node remotely

Is it possible to connect to any synced ethereum node remotely and query their blockchain? Also, if the former is possible then are there any known remote nodes that offer this functionality for free? ...
0
votes
0answers
20 views

Is it possible to use ganache blockchain when I deploy my web app in heroku? or should I deploy the contract first to a test network?

const web3 = new Web3( new Web3.providers.HttpProvider( "https://kovan.infura.io/v3/INFURA_KEY" ) ); const abi = JSON.parse( '[ { "constant": false, "inputs": [ { "internalType": "string", "...
0
votes
2answers
16 views

solidity declarationerror identifier not found or not unique for voting

I have this code for a voting system but when I compile it give me error in here ( boolean if_voted; ) can any one help me please. thank you this is the code : pragma solidity >=0.4.22 <0.7....
0
votes
1answer
14 views

Question about transaction confirmation

My question is that when a miner broadcast some transactions and other nodes don't think these transactions are valid, what will happen? Fork?
0
votes
0answers
21 views

Error: VM Exception while processing transaction: revert at PromiEvent When calling variable function from the deployed contract variable

I am new to blockchain and development and learning from the dapp university tutorial. I have created a contract Todolist.sol pragma solidity ^0.5.0; contract TodoList{ uint public ...
0
votes
0answers
16 views

PORT ERROR!! Set up a Private Ethereum instance with Geth on MacOS

Hello I am trying to set up a private ethereum instance with geth on MacOS I have a startnode.sh file using ATOM But every time I try to start the node with "./startnode.sh", the http access account ...
0
votes
0answers
17 views

How to pass a selected radio button value in reactjs to ethereum blockchain

I am new to react and ethereum. I am working on voting dApp where I want to pass the selected candidate with a radio button in react to the blockchain. How do i go about it? here is my code. I have ...
0
votes
0answers
16 views

How to create blockchain nodes locally

For educational purposes I am implementing a blockchain from scratch without the use of any frameworks. How would I go about testing my blockchain using multiple nodes when I only have access to one ...
0
votes
0answers
24 views

Migrating 2 contracts in one Contract.sol script using 'truffle migrate'

I have 2 contracts in 1 .sol file and when I run 'truffle migrate', it tells me that it has deployed 1 of the contracts and given me an additional error: Blockquote Invalid number of parameters ...
0
votes
1answer
64 views

Store and Display the Json file in Blockchain

I have stored my data on firebase, and taken as a JSON file, the JSON should be separated and display into the webpage through the Ethereum blockchain, for example: { product: "Shoes", prize: "85"...
0
votes
0answers
30 views

Retrieving the first and latest transaction date of a contract

Etherscan offers a time series of ethereum transaction of a contract address. Is there a way to retrieve this data? For example the duration mentioned here https://etherscan.io/address/...
0
votes
0answers
47 views

Api to get total transfer count of an ERC-721 Token

I want to retrieve the total number of an erc 721 token's transfers/ transactions. I couldn't scrape the transfers value from etherscan as well e.g. given here https://etherscan.io/token/...
0
votes
0answers
77 views

Unable to Unlock Account Even After specifying allow-insecure-unlock

Software: Ubuntu on VirtualBox Update, tried putting two dashes, on allow-insecure-unlock, doesn't work solidity@solidity:~$ geth attach http://127.0.0.1:8545 --allow-insecure-unlock Incorrect Usage:...
0
votes
0answers
39 views

blockchain solidity tracking system

I am trying to make a code in solidity to add items to a blockchain which contains items and their tracking history (like when trace your order online for an item) (which at first are located in "...
0
votes
1answer
18 views

How to substitute attributes instead of roles in access control coding for solidity?

Say, the role-based access control consists of two roles. But if I want to replace the roles to maybe location and time, how to go about it?
0
votes
0answers
8 views

CI/CD principles for creating an ethereum network on Cloud

I am setting up an ethereum network on the public cloud. Are there any specific CI/CD principles specific to Ethereum which could be implemented while setting up Ethereum Network on Cloud? Also, are ...
0
votes
1answer
47 views

getPastEvents on localhost is not a function error

Now, I'm working on an Ethereum Blockchain project to transfer the ownership of stored devices by using local web3 provider at the truffle environment. Truffle v5.0.27 (core: 5.0.27) Solidity v0.5....
0
votes
0answers
18 views

Can we connect custom Ethereum currency through java's web3j library ? If yes then how?

Im trying to create my own new currency using solidity and ethereum platform and also i want to create an Ewallet of my currency using java so that my ewallet could communicate through api .If u ...
0
votes
1answer
37 views

Why do I always get “Returned values are not valid, did it run Out of Gas”?

I'm new on Ethereum blockchain and I'm working on deploy and using smart contract using truffle on my private blockchain. I have followed exactly this guide https://www.trufflesuite.com/docs/...
0
votes
0answers
21 views

How to find out in blockchain ledger the current ownership of asset being transacted

I am new to blockchain and smart contract as well. In smart contract we can only save the current state of any transaction but if we need to know the previously expunged transactional data ie, the ...
0
votes
0answers
36 views

How simulate blockchain and smart contract in VANET?

I am a beginner in the blokchain, I am blocked how I start simulate a blockchain and smart contract in vanet. Can you help me and inform me how I have to simulate blockchain and smart contract in the ...
0
votes
2answers
31 views

validation of data integrity in block

I am learning ethreum dapps development and have developed some dapps. I was thinking about supply chain dapp which i think , is very good application of blockchain as it ensures all the history of a ...
0
votes
0answers
31 views

How Merkle Patricia Trie updates the account balance?

This is my understanding of the Merkle Patricia Trees in Ethereum so far: There are three kinds of merkle trees storing diff info - state, transaction and receipt. When a new block is added it ...
0
votes
0answers
39 views

How to transfer ERC20 token from one account to another account but paying the transaction fee from third account?

I want to transfer token from account A to account B by paying transaction fee from account C.I have tried the following logic but token transfer from contract to contract mean contract transfer token ...
0
votes
0answers
26 views

How to build an ethereum based wallet with custom UI?

I have been interested in ethereum for quite some time now and have always wanted to learn ethereum development. I decided to create my custom erc20 tokens i was able to create 2,00,000 tokens. Now i ...
0
votes
0answers
161 views

web3.exceptions.BadFunctionCallOutput: Could not decode contract function call getEvidence return data b'' for output_types ['string']

Solidity Code: function getEvidence(string memory _evidenceID) view public returns (string memory) { require(evidenceOwner[_evidenceID] == msg.sender); string memory evidenceHash = ...
0
votes
0answers
13 views

Can we treat/launch private ethereum chain ethers as a CryptoCurrency in Market?

Warm Greetings! I have a private ethereum blockchain setup on my server with multiple nodes , Also running mining software to mine blocks and earning private ethers (no value in market). Can i ...
0
votes
1answer
118 views

How do I deposit an Ether amount to the smart contract function, namely deposit ? (Metamask version 0.20.7)

I have a problem with using the deposit () function on a smart contract. How do you use metamask 0.20.7 ? const contractInstance = web3.eth.contract(contractAbi).at(contractAddress); contractInstance....
0
votes
1answer
29 views

Two smart contracts interact can't pass value when I using web3.js

I have two different smart contracts interaction_1 and interaction_2 I input the data(team) from remix ide. What I want to accomplish is when user input team in user_input function at interaction_1,...

1
4
5
6 7 8