Security

Selfdestruct: force another contract to receive your ethers.

Apr 1, 2022 · 1 min read · receive fallback selfdestruct ·

Insert Lead paragraph here. "Smart Contract receive ethers ONLY when contract provide fallback() or receive() function. " Is this statement true or not? [ ] true [ ] false 1pragma solidity ^0.8.0; 23// SPDX-License-Identifier: MIT 4contract MyContract { 5receive() external payable {} 6fallback() external …

Beware of using tx.origin to verify user

Mar 30, 2022 · 3 min read · Phishing ·

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According to Solidity doc, msg.sender (address): sender of the message (current call) tx.origin (address): sender of the transaction (full call chain) tx.origin means the first account that initial transaction. However, the msg.sender is exactly the account that triggers the function. Example Let's take a look at …

Don't use Blockhash as a source of randomness

Mar 21, 2022 · 2 min read · randomness ·

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Random is important in blockchain games. However, there is no true random number on solidity. The best practice is to use Chainlink VRF. This article will show you how to attack a CoinFlip contract. The following code is the CoinFlip contract, which was rewritten from Ethernaut. 1// SPDX-License-Identifier: MIT 2pragma …