All Questions

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0answers
1 view

Ethereum mining on the Hades Canyon NUC8i7HVK

Has anybody successfully used the GPU on the NUC8i7HVK to mine Ethereum. If so I'm looking for a way to do this. Thanks.
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0answers
5 views

ETH 2.0 but I have yet to claim my ETH from presale

Had to deal with life and lost track of ETH after the crash. I have yet to claim my ETH presale and wanted to know with all the forks and now ETH 2.0, can someone go over the best way to claim my ETH ...
0
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0answers
4 views

cannot read property score of undefined

Okay so i was setting up a frontend for a game server and i changed the table it uses in users.js after i restarted the web server and tried to login it gave me this error "(node:9347) ...
0
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0answers
9 views

How to check whether a contract has certain function?

How to check whether a contract has a function with certain name (with web3js)?
1
vote
0answers
8 views

DeclarationError:Identifier not found or not unique

pragma solidity >=0.4.22 < 0.6.0; pragma experimental ABIEncoderV2; contract BloodDonationProcess { struct LongTermInformation { bool allergies; bool diabetes; bool ...
0
votes
1answer
12 views

Where I can find the response in the blockchain (transaction inputs) or storage file in smart contract (resultat of transaction)?

when a user sends a tarnsaction to define the access control of a resource to a device s1,then it will be executed by smart contract and the result of the transaction is stored in the storage file of ...
0
votes
1answer
10 views

Gas limit and transaction fee in clique POA chain

I set a private POA private chain using default setting of Puppeth tool. The gaslimit in genesis.json is: "gasLimit": "0x47b760" The decimal number of gasLimit is 4700000 then I start node by ...
1
vote
0answers
20 views

How to know if the token is ERC20 or ERC233?

as I stated on the title because I am very confuse on how to know if the token is ERC20 or ERC233. I bought Thore Cash on Mercatox and I didnt know if it is ERC20 or ERC233 but they said they ...
0
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2answers
29 views

How the blockchain accepts this smart contract?

When an agent deploy a smart contract, how blockchain accepts this smart contract and sends an address of smart contract to agent. 1-How the blockchain accepts this smart contract? 2-who accepts the ...
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0answers
14 views

DeclarationError: Undeclared Identifier. Did you mean “_data”? data = _data ^__^. All i want is to create a cryptocurrency

pragma solidity ^0.5.1; contract owner { address public owner; function owned() public { owner = msg.sender; } function set( string memory _data) public { data = ...
1
vote
1answer
19 views

Encryption in Solidity - and yes of course the plaintext will be visible

I am using Solidity to write an Ethereum smart contract. I have a specific use case that requires a piece of data to be encrypted on the chain, despite the fact that both the plaintext and the ...
-1
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0answers
9 views

compile and deploy truffle

could anyone help me with it tried to compile and deploy as you see in the picter. module.exports = { networks: { development: { host: "127.0.0.1", port: 8545, network_id: "*" // Match any ...
0
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0answers
14 views

invalid genesis file: invalid character ',' after object key

I am trying to created ethereum private network. platform - Windows , geth 1.8.27-stable I created C:\myeth\genesis.json. genesis.json { "config": { "chainId": 0, "...
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0answers
15 views

How to use the address.transfer(amount)?

Using this smart contract, I want to transfer from one account to another. Here is my simple smart contract : pragma solidity ^0.5.0; contract Subtract { address payable public minter; uint ...
0
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0answers
4 views

Pass a list of structs as a contract function parameter in web3py

I am using web3py version 4.9.2 and wanted to find out if there is any way to call a contract function with an array of structs as enabled by the new ABIEncoderV2 functionality? The relevant solidity ...
0
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0answers
19 views

How to configure miners in ethereum blockchain network?

There could be many nodes on blockchain network let say 10 nodes, so it's not necessary that all should mine the block to commit it. Is there any configuration of miner? Or how we decide it? Edit: ...
0
votes
1answer
11 views

Is there any library for estimates timestamp of future block?

I am in need of a library that estimates a date or some sort of timestamp when fed with a future block number (on mainnet or any major testnet). For instance, https://etherscan.io/block/countdown/...
0
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0answers
14 views

I can't find my address from MEW when i want to connect my ledger nano s

I have been holding for 6 or 7 months now and when I went to check myetherwallet today, I was unable to find my wallets with all my ETH and my ERC-20 tokens. I plugged in my ledger like I always did, ...
0
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0answers
5 views

Trouble with Parity in android project

Android-studio does not recognise Parity.How can i import it to my project?
0
votes
1answer
11 views

How to create a wallet file for existing account&

I found this way of creating a new ethereum account with web3j.But what if i want to create a wallet file for already registered account?i need this because most of the web3j functions require a ...
0
votes
1answer
14 views

How to modify geth node configuration after launch

Is it possible to modify geth configuration when the node is running? For instance, open a port, add more parameter flag to control geth node functions. I think maybe there are two ways: One is stop ...
-1
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0answers
12 views

I have a question on ZepKit

The ERC20 is implemented referring to the following article. https://blog.zeppelinos.org/getting-started-with-zepkit/ I confirmed Wallet.sol at the console of truffle. Why are the arguments of ...
0
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1answer
11 views

3 level ether transfer

contract foster{ vulnerable v = new vulnerable(); attacker a = new attacker(address(v)); constructor() public payable{ // a.deposit(address(v)); // transferring 3 ethers to ...
0
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0answers
8 views

How Transaction, account balance is retrieved from blockchain

As I understand, information is stored in terms of hashes in blockchain and these hashes are verifiable and irreversible - as in the information stored in hashes cant be retrieved / How information ...
0
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0answers
21 views

issue while deployment

Here is my smart contract on auctions: The file name is AuctionBox.sol pragma solidity 0.5.0; import "/Users/ri/auction12/contracts/Math.sol"; contract AuctionBox{ Auction[] public ...
0
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0answers
15 views

Unable to run the code

I need help. I was trying to create a smart contract and I checked this website (https://medium.com/openberry/ethereum-solidity-vue-js-tutorial-simple-auction-dapp-within-10-minutes-76ba48156b2?fbclid=...
1
vote
0answers
9 views

Trouble with personalUnlockAccount,web3j

I am creating android dapp for votings I am trying to check if user's credentials are right,so i use object of PersonalUnlockAccount class and function accountUnlocked().So the problem is that when i ...
0
votes
0answers
16 views

How to handle floating point number in Solidity?

I read that there is no support for floating point number in solidity, So how we can handle it. If I want to store 12.23 or something like that.
0
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0answers
9 views

Testing a Smart Contract on two different devices at the same time

So the goal is to have two computers each owning one account or just different addresses on MetaMask for example and connecting them to the same Smart Contract that is deployed on Rinkeby. Now how ...
0
votes
1answer
18 views

How to deploy Smart Contracts With Web3 Using Async/Await?

This is my Javascript code. I keep getting an error that states Error: No privateKey given to the TransactionSigner. at TransactionSigner._callee$ (/Users/payton/WebstormProjects/Esgro_DAPP/...
0
votes
1answer
13 views

Web3.js to decode encrypted data using my private key

It's very similar to this question: How to decrypt an encrypted message using metamask? who was put one year ago. As user, I would like to store data safely on the blockchain, data that I want to ...
0
votes
1answer
13 views

Smart contract breaches

I am new to solidity and smart contracts. I wanted to know that can a smart contract be broken? what if I have my own smart contract made for demo and I want to break it in terms of security? How do I ...
0
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0answers
6 views

Execute `transferFrom` after executing `approve` on erc20

I can not withdraw from adress specified by approve. truffle(development)> erc20.approve("0x9e26730bf972d6ae8840b8f6003a61f57e25ff92", 1).then(b=>res=b) { tx: '...
0
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0answers
15 views

Web3 Websocket Connection To Infura Rinkeby Ropsten

This is my Javascript code. I keep getting an error that states (node:30062) UnhandledPromiseRejectionWarning: TypeError: privateKey.startsWith is not a function I am using node 12.1.0 & ...
0
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0answers
2 views

is it possible to do data replication from on-premise sql server to cosmos db

do we have the concept of data replication from on-premise sqlserver to cosmos db, if yes what are the steps to do mapping in the non relational db structure?I tried in searching in net,but i couldn't ...
2
votes
1answer
13 views

How to create a private ethereum network

I want to understand how to create a private blockchain using ethereum and create a minable coin. Also, I want to know if I can modify the consensus algorithm that runs on every node? There are ...
0
votes
1answer
8 views

Why did cryptokitties congest ethereum network when it has resizable block size?

So I am wondering how come eth network got congested when block size is resizable and it can take more trx if needed? I am reading some info that it can do that but miners don't want to do it as it ...
0
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0answers
17 views

how much structure variable does solidity support?

Error: "UnimplementedFeatureError: Variable inaccessible, too deep inside stack" code: contract create{ struct s{ string s1; string s2; string s3; string s4; ...
0
votes
1answer
16 views

I have msg.sender issue

Lets suppose here are user A and smartcontract B and C(sort of regular dapp). A has no token but little ETH for gas, but B has enough tokens(Erc20). A send TX to B B send call to C C receive tokens ...
0
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0answers
10 views

Want to understand token migration

Can anyone please explain the process of Token migration from one network to another network, Like omesi go and tron has done. they first lauch there own ERC20 token over ethereum and later migrated ...
0
votes
1answer
8 views

org.web3j.protocol.exceptions.TransactionException: Transaction receipt was not generated after 600 seconds for transaction

I am sending a transaction through this code public String transferEthByPk(String amount, String toAddress, String privateKey, Web3j web3j) { BigDecimal value = new BigDecimal(amount); ...
-1
votes
0answers
19 views

Why we buy Bitcoin or other cryptography with real money? [on hold]

In real world we don't purchase money with money, we get money by earning it, by doing some professional work and money is the reward of that work. Then we use money to purchase some things like (food,...
1
vote
1answer
10 views

Web3-eth-debug “Debug is not a constructor”

I use nodejs to execute a javascript that interacts with my local instance of Ganache. I would like to use the web3-eth-debug module to get information about my transactions. However after installing ...
1
vote
0answers
17 views

How to obtain the msg.sender in truffle console?

Here is my code snippet to return the msg.sender: function showSender() public view returns (address) { return (msg.sender); } But when I try to call this function using this: Coin....
0
votes
1answer
15 views

Sending the bool to ```function() payable``` in another contract

I am trying to create a pair of contracts, let's say C1 and C2. I want to add an if...else in payable function function() public payable{} of C2, which works on the bool value returned by contract C1, ...
0
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0answers
23 views

Can value of a public variable in Solidity be called and returned by web3?

How to get value of a public variable in Solidity be called and returned by web3?
0
votes
1answer
12 views

Cannot call function even though it is present in the jsonInteface

I have a simple contract with a simple test-function: pragma solidity ^0.5.0; contract TestContract{ uint public a; uint public b; constructor(uint _a, uint _b) public { a = _a; b = _b; } ...
0
votes
0answers
24 views

Hoiw to convert string to address with web3

I am getting address value with html input as string value how do we convert the string to address for parsing with truffle-contract. Here's the method I am using: registerAirline : async() => {...
0
votes
0answers
15 views

What are blockchain interview quesetions? [on hold]

What are some best blockchain, ethereum and smart contract interview question that I must know ?
0
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1answer
11 views

How to view or transfer initial ethereum smart contract balance?

I created a new smart contract token with initial supply and deployed it via MetaMask. Then I added this token into MetaMask but token balance is Zero. Now, My question is when we create a new ...

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