precompiles

Precompiles are fixed, native routines exposed to the Ethereum Virtual Machine at predetermined addresses. They are implemented in the client software and run as native code rather than as EVM bytecode, allowing cryptographic and other computationally intensive operations to be performed more efficiently. Calls to a precompile look like a contract call, but execution occurs outside the EVM interpreter, with gas costs defined by the protocol and typically related to input size or operation type.

Common precompiles cover a range of cryptographic and data-processing tasks. Examples include ecrecover, which recovers an Ethereum public key from a signature; sha256 and ripemd160, which perform standard hash functions; and identity, a no-op that returns its input. The modular exponentiation precompile supports large integer exponentiation. On the BN128 (alt_bn128) curve, there are precompiles for addition, multiplication, and a pairing check, which are especially useful for zk-SNARK and other cryptographic protocols. These primitives are used by smart contracts to verify signatures, perform proofs, or process data efficiently without incurring the higher costs of equivalent operations in pure EVM code.

The set of precompiles is defined by the protocol and is not typically upgraded through ordinary contract deployment; changes require protocol hard forks. As a result, precompiles provide predictable gas behavior and cross-network interoperability within a given blockchain client implementation. They play a central role in enabling efficient cryptographic verification and other heavy computations within smart contracts and layer-2 systems.