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Cryptocurrency Development Ethereum

So can I simply send ether to a contract as if it’s a regular wallet, even without payable function?

Are contracts really that different? I guess in theory every contract should have a private key somewhere + it should be possible to send ether to it? Unless geth/parity and other parts of the evm don’t have functions specifically checking if every blockchain transfer is wallet vs contract and hence rejecting ether if it’s send […]

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Cryptocurrency Development Ethereum

DAPP Send Button should show ENS in Metamask

My DAPP has a “Buy” Button. On clicking this button, after some checks, Metamask (if that is the wallet that the user is using) will open up and show a transaction of sending XX ETH from his wallet to an address. Is it possible that Metamask shows the ENS address in the pop-up rather than […]

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Cryptocurrency Development Ethereum

Get contract data if all I have is a contract address

I have the address of a smart contract and I need to get the data residing in that address. I seem to have been struck at this for a while now and I want all this inside a smart contract. pragma solidity ^0.4.8; contract myContract { address[] public childContracts; function newContracts(uint _id,string _name) public returns(address […]

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Cryptocurrency Development Ethereum

REMIX debugger invalid opcode before JUMP

I am testing simple ERC20 token creation with the following in remix: pragma solidity ^0.5.0; import “https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.4.0/contracts/token/ERC20/ERC20.sol”; import “https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.4.0/contracts/token/ERC20/ERC20Detailed.sol”; contract TestToken is ERC20, ERC20Detailed { constructor () public ERC20Detailed(“TestToken”, “TKN”, 18) { _mint(msg.sender, 1000000 * (10 ** uint256(decimals()))); } } I launch the contract and debug, but prior to every JUMP opcode, i receive an […]

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Bitcoin Cryptocurrency Development

Create hashes with at least a user-selected number of leading zeroes

The main program consists of a simple menu with two options: • Try to find nonces that can create hashes with at least a user-selected number of leading zeroes • Quit When the user chooses to start generating hashes, those calculations will continue until the user presses ctrl+c. • Once the user does press ctrl+c, […]

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Cryptocurrency Development Ethereum

Creating ethereum account during user registration

There is a site with simple registration and user login. How can I create a new ethereum account for each new user and store the keys of these accounts in my database

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Cryptocurrency Development Ethereum

Insufficients funds to Deploy Contract on Test Network

Here are my files on github, https://github.com/ArtieLadie/gas_limit https://github.com/ArtieLadie/gas_limit/blob/master/deploy.js sets gas limit here, async function deployContract(web3, contract, sender) { let Voter = new web3.eth.Contract(contract.abi); let bytecode = ‘0x’ + contract.evm.bytecode.object; let gasEstimate = await web3.eth.estimateGas({data: bytecode}); This is the account I am using to deploy contract. It has 18 ether. https://rinkeby.etherscan.io/address/0xf8f07fc5301d4644ab33f59496a03363233b8f79 When I deploy contract, I […]

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Bitcoin Cryptocurrency Development

Wallet validation methods (centralized, SPV, etc.) – please clarify for Ledger and in general

1) ledger: https://bitcoin.org/en/wallets/hardware/ledgernanos/ Variable validation – Payment validation features are provided by the software wallet you use with this device. 2) wasabi: https://bitcoin.org/en/wallets/desktop/windows/wasabi/ Centralized validation – This wallet relies on a centralized service by default. This means a third party must be trusted to not hide or simulate payments. 3) Simplified validation (SPV) – This […]

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Cryptocurrency Development Ethereum

What is the role of uncle blocks in improving the transactions throughput?

Here, it is said that the transactions of uncle blocks are not included in the main chain. Then, what is the reason of making the block creation time shorter in Ethereum (15 seconds instead of Bitcoin’s 10 minutes) which leads to have so many forks? If the reason of shorter block creation time is improving […]

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Cryptocurrency Development Ethereum

Transaction unsucessful on localhost but sucessful via remix [on hold]

Contract pragma solidity ^0.5.0; import ‘./Patient.sol’; contract Doctor{ uint public doctorCount = 0; uint public treatCount = 0; bytes32 public p_id=0; uint public key=0; address addressP; uint[]p; mapping(uint => Info) public info; mapping(uint => PatientList) public patientlist; bytes32[] waitlist; // mapping(uint=> WaitList) waitlist; // struct WaitList{ // bytes32[] wait; // } struct PatientList{ uint pid; […]