All Questions

I'm getting an error when trying to connect to ropsten from Terminal, using the following command: truffle console --network ropsten Here's the error: truffle(develop)> truffle console --network ...

Can you recommend some php script to sign transaction.Thanks.I want to find some php script to sign transaction and without using web3.

While reading the transactions sections of EVM documentation many questions raised in my head: If the target account is not set (the transaction does not have a recipient or the recipient is set ...

I'm new at ethereum, new at blockchain development at all, and am wondering how can I validate simple money transfer from one address to another? I'm querying the blockchain with etherscan and have ...

Can someone suggest me how to use estimateGas for function calls like below: await (MyContract.methods.addDoc(id,sha256hash).send({from: coinbase[0],gas: 1000000})

friends My application having the needs to detect newest transaction from a EOA, and I am going to use https://etherscan.io's API. To reduce transaction scanning, I decides to recording the last ...

I can see from this site - https://etherscan.io/chart/gasused - the amount of gas used on the Ethereum network daily. What I cannot work out is how much ETH that corresponds to. Is there some other ...

web3.eth.getBlock(12345).then(res => { connection.query(`INSERT INTO blockdata(bnumber,btimestamp) VALUES ("${res.number}","${res.timestamp}");`) }); I got timestamp already. I wanna insert data ...

What is the standard length of words in the mnemonic phrase for various ethereum wallets ? I need to know this in order to decide what should be the choices given to the user while creating a ethereum ...

This is about the parameters that we need to provide at the time of source code verification on Etherscan. I have a bit idea about it but i am looking for some deep and clear explanation. So my ...

I am new in solidity and trying some small code however I am getting error which I could not find. I am trying below code pragma solidity >=0.4.0 <0.6.0; contract property { uint public ...

I am trying to create asset based transfer Smart contract by solidity language. i'm using ethereum. functions are Create assets (land_id, land_size, land_price) with a ownership of contract owner. ...

I am having a Mainnet on Azure VM which was syncing the network as expected, but mean while after adding Ropsten network syncing on the same VM simultaneously I'm facing problem with Mainnet sync ...

Iam using Android studio with webj3 API to use smart contract deployed in the local machine using Ganache and Truffle Security.removeProvider(BouncyCastleProvider.PROVIDER_NAME); Security....

Complete newbie here so thanks in advance for tolerating the ignorance that follows. Working on creating a little card game to learn solidity and have reached the part where I need to assign metadata ...

Is it possible to include in a payable function a message such as "Transaction rejected - Company not registered" which is displayed when a transaction is rejected? My code is as per below: ...

function compare(string memory input, uint _y) public returns (uint){ bytes32 hashedinput = keccak256(input); } Error: Invalid type for argument in function call. Invalid implicit conversion from ...

After making all the client side scripts inside a folder which are needed for my website (in dist folder) checked with ipfs swarm peers : shows many results then adding the files with ipfs add -r ...

I am following this tutorial to setup a Quorum cluster: https://medium.com/@shizekun/how-to-set-up-a-quorum-private-chain-with-raft-consensus-and-dynamic-membership-bf826f3927e5 But unfortunately I ...

Is there a way to send ether from several input addresses in one transaction WITHOUT the use of smart contracts? I wish that different transactions could not be linked to each other. A similar ...

I might be wrong in some of the facts that I state here, so please correct me if necessary. My understanding: Private key - 256 bits Public key - 256 bits Public address - the last 160 bits of a ...

It seems that when using the latest solidity-coverage (0.5.11), truffle (5.0.0-next.25) ganache-cli (6.2.4-beta.1) and solc (0.5.0) additional events / logs are emitted during tests which make the ...

Does anyone knows apps that use the concept of proof-of-stake of ERC20 tokens? For example, applications like STEEM, that uses and its STEEM POWER. "STEEM Power is what gives you influence on Steemit....

I start ethereum with command: geth --syncmode fast --cache 256 and I find my files in ~/.ethereum/geth/chaindata are like: 000390.ldb 000392.ldb 000420.ldb 000484.ldb They are not one after one. ...

I recently upgraded Web3JS and Solc. Now every time I pass a zero address to a Solidity contact method the transaction reverts with an "invalid address" message. This message appears to be coming ...

I was wondering why is the eternal storage approach (first code snippet) still used? I know it's meant to make contracts upgradable but it seems too expensive to me. contract Storage { mapping(...

I had a MetaMask account with password. Had used password to connect to DDex exchange for Ethereum connectivity, transactions, and token balance checks. Recently, I deactivated MetaMask from one of ...

Metamask (or other browser plug-in) helps a lot the user to submit transactions using his personal account since it manages his private keys. When interacting with an dapp front-end, web3 will ...

If want to integrate ERC20 token to integrate as paymen to a website. how can?

As above, is ApproveAndCall also vulnerable to double withdrawal attack? https://www.reddit.com/r/ethereum/comments/6uckdx/reminder_about_problems_of_most_erc20_tokens/

I saw a Solidity smart contract where some variables were declared with the type address and some were declared with the type address payable. What are the differences between the two? Do they store ...

I was wondering... Will Constantinople hard fork surely replace the current fork? Is there any chance that the Constantinople fork and the current one will co-exist? If so, any replay attack ...

I'm working with oraclize and Solidity and I need to get a URL of the API to query, usually "json().XX". The expected format is a JSON object with 2 fields or string like so: { "portfolioValue": 100....

I have the following code for a simple gambling game. The code works fine except for getPlayers function pragma solidity >=0.4.22 <0.6.0; contract Lottery { address payable public manager; ...

I have problem that if I created ethereum token and I want to use it in real project . especially in payment gateway . How can integrate ethereum token as payment in ecommerce website and how can ...

Basically I have a dapp that gets the web3 object from window.web3 (the injected from metamask). When i disable de extention from chrome (not removing, just disabling) the web3 invocations are ...

Can some body please guide me how to install Oyente on Windows 10? I have found Oyente for Linux but not for windows on github. Some body please guide me. Zulfi.

I am trying to compile the following contract on Remix IDE (online): pragma solidity ^0.4.24; contract ProofofExistence{ event ProofCreated( uint256 indexed id, bytes32 documentHash);/...

I have followed the truffle petshop tutorial and it runs in my local machine, I have a shared hosting account and i would like to upload and test this Dapp on my server to start to modify it. The ...

I am working on my first end to end ethereum project. A problem that I am stuck on is that I have installed 'truffle-contract', but when I run my server and open the project in the Chrome browser, the ...

My understanding of the DAO hack is that Ethereum was hard forked so that those who lost funds could have them retrieved. If the hacked funds were immediately converted to bitcoin, would this still ...

I'm trying to make a frontend of calling a function with an address attached: function getAvailableAllocation(address _addr) constant returns (uint ethAvailableAllocation) { return ...

I am using Oraclize for generating random number for my smart contract. I write unit test for testing oraclize things so I use ethereum-bridge written by Oraclize. Here is my problem: First: my smart ...

How can I define in truffle the ipc connection to the node? Currently I am using in truffle.js host/port fields, which are used to create a HttpProvider. module.exports = { networks: { dev: { ...

am using geth VRSION: 1.8.20-stable-24d727b6 and ethereum wallet Ethereum-Wallet-linux64-0-9-3 and i am using Ubuntu 18.04.1 LTS in the geth console i started the miner but either is not ...

whenever I want to run this code I get this error "Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending? VM ...

I have created contract on Ropston TestNet which will send any already created tokens. Unfortunately its giving me error Transaction Details Available at: https://ropsten.etherscan.io/tx/...

i am using geth VRSION: 1.8.20-stable-24d727b6 and ethereum wallet Ethereum-Wallet-linux64-0-9-3 and i am using Ubuntu 18.04.1 LTS and on wallet startup wallet is showing the error message here ...

I'm making a React frontend for an open-source blockchain protocol for tokenized hedge funds. So the question is how to provide the payable function that requires some other value attached (n this ...

I have a small contract pragma solidity ^0.4.17; contract A10test{ mapping(uint=>string) public data; uint public revisionNo=0; function setdata(string _data) public { data[revisionNo] = ...