A precompiled contract, in the context of blockchain technology, particularly Ethereum, refers to a special type of smart contract that is built into the blockchain protocol itself. Unlike regular smart contracts, which are written in languages like Solidity and deployed by users, precompiled contracts are hardcoded into the Ethereum Virtual Machine (EVM) and are executed in a highly optimized, native way. Here’s a breakdown of what makes precompiled contracts unique: 1. **Purpose**: They are designed to perform specific, commonly used cryptographic or computational functions efficiently. These operations would be too expensive or slow if implemented as regular smart contracts in Solidity. 2. **Efficiency**: Since they are implemented at a lower level (in the client software, like Geth or Parity), they consume significantly less gas (the unit of computational cost in Ethereum) compared to equivalent operations in a user-deployed contract. 3. **Fixed Addresses**: Precompiled contracts reside at predefined addresses on the Ethereum blockchain, typically from `0x1` to `0x8` (though more can be added in future upgrades). For example: - `0x1`: ECRecover (recovers the public key from an elliptic curve signature) - `0x2`: SHA256 (computes the SHA-256 hash) - `0x3`: RIPEMD160 (computes the RIPEMD-160 hash) - `0x4`: Identity (returns the input data unchanged, used for cheap data copying) 4. **Examples of Use**: They are often used in scenarios requiring cryptographic verification (e.g., signature validation) or data hashing, which are critical for security and interoperability in decentralized applications. 5. **Not User-Deployed**: Developers don’t create or deploy precompiled contracts; they simply call them by sending a transaction or message to their fixed addresses with the appropriate input data. In essence, precompiled contracts are a performance optimization in Ethereum, providing fast, low-cost access to essential functions that would otherwise burden the network if implemented in standard smart contracts. They’re a foundational part of the blockchain’s infrastructure, balancing efficiency with the flexibility of programmable smart contracts.