While OpenZeppelin is a widely used and respected smart contract library, there are alternative libraries that offer improved gas efficiency. Two notable examples are Solmate and Solady. These libraries have been tested and recommended by developers for their focus on gas optimization.
Pseudo-Random Numbers
Smart contracts often maintain state variables that track balances. However, direct transfers not mediated by contract functions (like direct Ether sends to a contract address or transfer calls for ERC20 tokens that bypass the contract's logic) can create discrepancies between the actual balance held by the contract and the balance recorded in the contract’s internal state variables.
Incrementing operations are fundamental in contract development due to their frequent use in counting and looping mechanisms. Each method of incrementing has subtle nuances that may affect gas consumption and readability:
In Solidity, the type of data storage you choose can affect the gas cost of your contract operations, especially when storing or modifying state variables. The Ethereum Virtual Machine (EVM) charges gas for all operations, and the choice between using bytes32 and string types can impact these costs.
In factory contracts, we often need to create several child contracts, and there are three common ways to do this:
In the Ethereum Virtual Machine (EVM), the selection of comparison operators influences the efficiency and gas consumption of smart contracts. Opting for ` (greater than) over ≤ (less than or equal to) and ≥ (greater than or equal to) is notably more gas-efficient. This is due to the absence of direct opcode instructions for ≤ and ≥` in the EVM's design, which requires additional operations to achieve these comparisons.
In Solidity, how you initialize state variables can have a impact on the deployment cost of your contracts, specifically in terms of gas usage. The Ethereum Virtual Machine (EVM) requires gas for every operation, including the initialization of variables.
This tutorial explores how using storage pointers instead of copying data to memory can result in substantial gas savings. Storage pointers allow developers to directly reference storage without unnecessary copying of data, leading to more efficient smart contract execution.
ERC20 transfer issues are a common source of vulnerabilities in smart contracts. These issues arise from inconsistent implementations of the ERC20 standard, particularly in how different tokens handle the return value of transfer functions.
In standard ERC20, users typically need to execute two separate transactions:
Excessive function restrictions in smart contracts can lead to critical issues such as funds being locked, which can prevent rightful access even in necessary situations. A well-documented example is the Akutars NFT incident, where $34 million in Ethereum was trapped due to overly restrictive contract mechanics intended for security.
In Solidity, the way you manage and interact with arrays can impact the gas cost of your smart contract operations. This tutorial demonstrates the difference in gas usage between fixed-size arrays and dynamic arrays when they are filled with values. This understanding can help developers make more cost-effective decisions when designing smart contracts.
Flashloans are a powerful feature in decentralized finance (DeFi) that allows users to borrow assets without collateral, under the condition that they return the borrowed amount within the same transaction. This feature has enabled unique financial strategies, but it also poses significant risks for governance systems.
降低 gas 费用的小窍门
If access control is about controlling who calls a function, input validation is about controlling what they call the contract with. This usually comes down to forgetting to put the proper require statements in place.
1. memory : 通常用于修饰函数参数和函数内的临时变量。 此类变量存储在内存中，不会永久保存在区块链上。
When transactions are executed by the Ethereum Virtual Machine (EVM), the accompanying calldata, which specifies the contract function to be executed, incurs gas fees. These fees are calculated based on the calldata size, with 0 bytes costing 4 gas units and non-0 bytes costing 16 gas units. This pricing structure encourages the efficient use of calldata to reduce transaction costs, especially in contracts with high transaction volumes or complex operations.
In the contract, all functions are organized into an array and systematically sorted by their MethodID, a unique identifier for each function. This organization not only streamlines the management of function calls but also facilitates quick access by imposing a structured order that can be efficiently searched during function executions.
In Solidity, the choice between using modifiers and internal functions can impact the gas costs associated with contract operations. This article explores the differences in gas usage between modifiers and internal functions when performing typical operations. 了解这些差异可以帮助开发者优化他们的智能合约，以优化合约功能并控制成本。
When developing smart contracts, security is one of the most critical considerations. This tutorial will delve into a common but dangerous pattern: using msg.value within loops. We'll explain why this is dangerous and provide some best practices to avoid related vulnerabilities.
Initializing a storage variable from zero to a non-zero value is one of the most gas-intensive operations a contract can perform. It requires a total of 22,100 gas, including 20,000 gas for changing the value from zero to non-zero and 2,100 gas for cold storage access.
In Solidity, the way data is stored can significantly impact the gas costs associated with deploying and interacting with smart contracts. Gas costs can quickly become a major concern, especially in applications that handle a large number of transactions.
变量打包
In Solidity, predicting contract addresses before their deployment can save substantial gas, especially when deploying interdependent contracts. This method eliminates the need for setter functions and storage variables, which are costly in terms of gas usage. We can use the LibRLP library from Solady to deterministically compute the addresses based on the deployer's nonce.
Price manipulation poses a significant risk to smart contracts that utilize decentralized exchanges (DEXs) like Uniswap, where asset prices are influenced by the liquidity within trading pools. These pools are vulnerable to manipulation by well-resourced entities capable of altering market balances to artificially influence prices. Such manipulative actions can severely undermine the functionality and security of financial applications that rely on this pricing data for essential operations.
In Solidity, using the delete keyword to remove a state variable resets it to the default value for its type. The default values differ according to the data type:
In Solidity, downcasting from a larger integer type to a smaller one can be hazardous due to the lack of automatic overflow checks in versions before 0.8.0. This tutorial explains the risks of downcasting, provides an example of a problematic function in older Solidity versions, and offers a solution using a library like SafeCast to ensure safe operations. Even though Solidity 0.8.0 and later versions include built-in overflow checks, using SafeCast can enhance code clarity and safety.
The selector collision attack was one of the key reasons behind the hacking of the Poly Network cross-chain bridge.
Signature Replay Attacks
Conflux 网络智能合约开发介绍
The cost of executing transactions on the Ethereum network can be very high, especially when interacting with smart contract storage using the SSTORE opcode. To mitigate these costs, developers can leverage alternative methods like SSTORE2 for more efficient data handling.
A transaction origin attack is form of phising attack that can drain a contract of all funds.In Solidity, tx.origin retrieves the address of the transaction originator, distinguishing it from msg.sender.
在Solidity中，通常认为使用较小的整数类型如 uint8, uint16, uint32, uint64, uint128, 和 uint256 可能会因为它们的尺寸较小而节省gas。 然而，情况并非总是如此。
We know that before the Solidity version 0.8, it was necessary to manually import the SafeMath library to ensure data safety and avoid overflow, thereby preventing overflow attacks.
Unchecked low-level calls are a common source of vulnerabilities in smart contract development. These calls include call(), delegatecall(), staticcall(), and send(), which do not revert the transaction when they fail but instead return a boolean false. Failing to check these return values can lead to critical security issues.
This tutorial explores how making the architecture of your smart contracts monolithic, rather than having several contracts that communicate with each other, can result in gas savings. Inter-contract calls can be expensive, and by consolidating logic into a single contract, you can avoid these costs, albeit with some trade-offs in terms of complexity and modularity.
In Solidity, leveraging the payable keyword can be a subtle yet effective way to optimize gas usage. In this article, we explore two distinct scenarios where using payable can lead to gas savings: in constructors and admin functions.
In Solidity, optimizing gas usage is crucial for creating efficient smart contracts. One technique involves using the selfdestruct function within the constructor for contracts designed for one-time use. This approach can reduce gas costs by eliminating the contract from the blockchain once its purpose is fulfilled.
When designing upgradable smart contracts, gas efficiency is critical for users interacting with the contract. There are two common upgrade patterns: UUPS (Universal Upgradeable Proxy Standard) and the Transparent Upgradeable Proxy. While both enable upgradability, the UUPS pattern is generally more gas efficient for users.
在区块链上存储数据的成本极高。 很多项目创新性地使用了一些巧妙的方法来降低gas费用。 我们今天将会讨论那些常见于 龙头项目的源代码中的方法。
在智能合约中使用修饰符进行重入检查可以通过确认合约当前是否正在执行来提升安全性。 通常，布尔型标志用于控制访问权限，只有当合约尚未激活时才允许函数运行。
在 Solidity 中，可以通过将多个状态修改调用批量处理为单个交易，以在路由器类合约中实现多调用功能，显著降低燃气成本。 这种技术在像 Uniswap 和 Compound 平台的合约中非常有价值。
在许多常见的DeFi项目中，我们经常遇到需要定义许多新的局部变量和更新现有全局变量的各种复杂计算。 众所周知，修改存储比在内存中进行更改的成本要高得多。
1. 常量(constant): 声明一个常量，必须在声明时进行初始化,之后不能再被改变。
In April 2022, a popular NFT project called Akutar conducted a successful Dutch auction to raise funds, amassing 11,539.5 ETH. However, when processing refunds for previous community pass holders, a flaw in their smart contract prevented operations, locking all funds within the contract due to a DoS vulnerability.
2018年4月，BeautyChain（BEC）代币上发生了一起涉及整数溢出漏洞的重大事件。 该漏洞使攻击者能够凭空生成大量的BEC代币，导致了巨额财务损失，并削弱了该代币的价值。
在 Solidity 中，不同的数据结构会显著影响因合约操作而产生的 gas 成本。 本文探讨了在执行插入、删除和检索等典型操作时，映射 和 动态数组 在 gas 使用上的差异。 了解这些差异可以帮助开发者优化他们的智能合约，以优化合约功能并控制成本。
什么是智能合约？
确保智能合约的安全至关重要，因为它们涉及财产的直接处理与存储，并且一旦合约被部署在区块链上，就很难修改。 为了保护你的智能合约，遵循以下关键步骤和最优的实践方法：
在Solidity中，每一个需要上链的操作都需要消耗gas，短路运算是一种编码技巧，它仅在第一个参数没有确定结果时才评估逻辑操作的第二个参数，从而显著减少不必要的gas消耗，提高效率。
许多免费铸造的项目使用 isContract() 方法限制对外部账户 （EOAs）的访问以及限制智能合约的交互。 此方法使用 extcodesize 来决定地址运行时 bytecode 长度。 如果大于零，则被视为智能合约；否则，它被视为EOA。
智能合约的访问控制漏洞是导致 Poly Network 跨链桥黑客攻击（损失 6.11 亿美元）的主要因素之一，并且也导致了在币安智能链（BSC）上的 ShadowFi DeFi 项目遭受 30 万美元的黑客攻击。
重入攻击是针对智能合约最常见的攻击类型之一，攻击者利用合约的漏洞递归调用合约，使其能够从合约中转移资产或者铸造大量的代币。
在Solidity中，开发者可以以三种主要形式定义错误： revert、 require 和 assert。 从功能角度来看，这些方法的主要区别有两个：