The Core Issue: libsecp256k1, Bitcoin’s Cryptographic Heart
libsecp256k1 is a crucial, high-quality, and performant C library handling Bitcoin's secp256k1 elliptic curve cryptography.Summary
The article details the history, evolution, and critical importance of libsecp256k1, the software library underpinning Bitcoin's digital signatures using the secp256k1 elliptic curve. Initially, Bitcoin used OpenSSL, which presented parsing inconsistencies that could risk chain splits, leading to its replacement by libsecp256k1 starting in Bitcoin Core v0.12 (2016). The library originated from Pieter Wuille's curiosity around optimizing signature verification using an endomorphism technique discussed by Hal Finney, resulting in a 2.5x to 5.5x speedup upon initial adoption, later boosted by 16% when the endomorphism optimization was fully enabled in 2020 after patent expiration.
libsecp256k1 focuses solely on secp256k1 operations, making it faster, simpler to review, and dependency-free, suitable even for hardware wallets. It maintains near 100% code coverage and employs exhaustive testing. A major milestone was implementing Schnorr signatures (BIP340) for Taproot. Crucially, the library prioritizes security, especially in signing operations, by implementing constant-time code to mitigate side-channel attacks and ensuring secret material is properly erased from memory. Its development, guided by 'full-stack cryptographers' like Wuille, Maxwell, Nick, and Ruffing, has also led to external discoveries, such as finding a bug in OpenSSL. The library continues to evolve, incorporating new standards like MuSig2 and preparations for Silent Payments.
(Source：Bitcoin Magazine)