Global Journal of Computer Science and Technology, D: Neural & Artificial Intelligence, Volume 23 Issue 2

1. The contract ‘SimpleBank’ allows users to deposit and withdraw Ether (the native currency of the Ethereum blockchain). 2. The ‘balances’ mapping stores the balance of each account. When an account deposits Ether, its balance is increased; when it withdraws, the balance is decreased. 3. The ‘deposit’ function allows users to deposit funds into their account. 4. The ‘withdraw’ function allows users to withdraws a specified amount of funds from their account. It first checks whether the user has enough balance to withdraw the requested amount before transferring the funds. Integer Overflow The ‘balances’ mapping uses the ‘uint256’ data type, which has a maximum value of 2^256 - 1. If a user deposits a large enough amount, it could cause an integer overflow when adding to their current balance. This would wrap the balance back to zero and effectively allow the user to withdraw the entire contract balance. For example, if an account with a balance of ‘balances [msg.sender] = 2^256 - 2’ tries to deposit 3, the balance will become 1 (due to overflow) instead of the expected value of ‘2^256 - 2 + 3’. Integer Underflow The ‘balances’ mapping is using the ‘uint256’ data type, which cannot represent negative values. If a user tries to withdraw more funds than they have, it could cause an integer underflow. In Solidity, underflow on a ‘uint256’ wraps the value to its maximum value (2^256 - 1). For example, if an account with a balance of ‘balances [msg.sender] = 100’ tries to withdraw 200, the ‘require’ statement will pass because ‘amount <= balances [msg.sender]’ evaluates to ‘false’ (since 200 is not less than or equal to 100), and the subtraction operation ‘balances [msg.sender] -= amount’ will wrap around to the maximum value of ‘uint25’, i.e., ‘2^256 - 1’. Prevention To mitigate these vulnerabilities, you can use safe math libraries like OpenZeppelin's SafeMath or, starting from Solidity version 0.8.0, use the built-in ‘checked’ arithmetic operations (e.g., ‘a + b’, ‘a - b’, ‘a * b’, and ‘a / b’) which automatically revert on overflow/underflow. iii. Denial of Service (DoS) attack DoS attacks directed at smart contracts represent a significant security threat. In these attacks, malicious individuals aim to disrupt the regular operation of the smart contract intentionally. The main goal is to render the smart contract unavailable to legitimate users, either temporarily or permanently. Such attacks can cause severe consequences, including the disruption of critical functionalities, suspension of contract execution, and depletion of resources. Ultimately, this leads to financial losses and disturbances in decentralized applications, making it a serious concern for the blockchain community. iv. Access Control Vulnerabilities Access control vulnerabilities in smart contracts refer to security flaws that arise when unauthorized users gain unintended access to certain functions, data, or funds within the contract. These vulnerabilities can have severe consequences, including loss of funds, unauthorized manipulation of critical contract logic, or unauthorized access to sensitive data. v. Timestamp Dependence Aulnerability Timestamp Dependence vulnerability refers to a security flaw in a smart contract where the contract's logic or behavior is influenced or manipulated by the © 2023 Global Journals Global Journal of Computer Science and Technology Volume XXIII Issue II Version I 61 ( )D Year 2023 Strengthening Smart Contracts: An AI-Driven Security Exploration