Introducing UltrafastSecp256k1: A Multi-Architecture Exploration of Secp256k1 Optimizations

The project, which was open-sourced in early 2026, aims to leverage modern hardware features such as SHA-NI, AVX2, and ARM64 Assembly to enhance ECC performance. This is crucial for both high-end x86 servers and resource-constrained IoT devices like ESP32-S3 and RISC-V boards. The library's design focuses on portability, constant-time operations, and branchless coding, making it accessible through bindings in over twelve programming languages including Rust, Go, Swift, and Dart.

A core aspect of UltrafastSecp256k1's architecture is its "Zero-Allocation" hot-path contract, which eliminates heap overhead during critical cryptographic operations. This efficiency is achieved through several optimizations, such as transitioning to a field representation for Point internals that allows __int128 lazy reduction in constant-time operations. Furthermore, the library implements constant-time field inversion using the SafeGCD algorithm and scalar multiplication through GLV Endomorphism, reducing cycle counts significantly. Hardware acceleration techniques, including SHA-NI for hashing and AVX2 for constant-time table lookups, contribute to the library’s high performance. To improve instruction cache efficiency, large functions are marked with noinline, considerably reducing I-cache misses.

Performance enhancements are evident in platform-specific implementations. For instance, on x86_64 architectures, Comb precomputation tables optimize operations, while ARM64 platforms benefit from hand-tuned multiply/square bypasses optimized for newer cores. The library also supports embedded systems, with optimizations for ESP32-S3 and planned improvements for RISC-V architectures, highlighting its wide applicability.

The latest updates include significant progress in RISC-V optimization, specifically for the Milk-V Mars (SiFive U74) chip, where in-order scheduling has led to a 34% increase in verification speed. This improvement is part of version 3.11, demonstrating the project's ongoing commitment to enhancing performance for IoT devices, where computational efficiency is paramount.

The project's GitHub repository (https://github.com/shrec/UltrafastSecp256k1) serves as a hub for collaboration, featuring a technical changelog (https://github.com/shrec/UltrafastSecp256k1/blob/main/CHANGELOG.md) that documents the continuous enhancements made to the library. The developer seeks feedback from the community on aspects such as constant-time integrity, algorithm selection, and suggestions for further reducing branches in the coding to bolster security. This collaborative approach underscores the importance of peer review in ensuring the tool remains fast, secure, and reliable for the wider ecosystem.