Introducing UltrafastSecp256k1: A Multi-Architecture Exploration of Secp256k1 Optimizations

UltrafastSecp256k1 is an open-source project initiated on February 11th, 2026, aimed at enhancing the performance of ECC (Elliptic Curve Cryptography) across a wide range of platforms. This project leverages advanced hardware features such as SHA-NI, AVX2, and ARM64 Assembly to meet the needs of both high-end x86 servers and resource-constrained IoT devices like the ESP32-S3 and RISC-V boards. Its design principles focus on portability, constant-time operations, and branchless execution, making it accessible through bindings in over 12 programming languages including Rust, Go, Swift, and Dart. The creator has invited the community for a technical audit, seeking feedback on the cryptographic primitives and the implementation of constant-time operations.

The architecture of UltrafastSecp256k1 emphasizes "Zero-Allocation" in its hot-path contract, which eliminates heap overhead during critical operations. Significant architectural components include a new field representation for Point internals using __int128 lazy reduction in constant-time operations, constant-time field inversion via the SafeGCD algorithm optimized for various architectures, and scalar multiplication improvements through GLV Endomorphism. Additionally, the use of SHA-NI for hashing and AVX2 for constant-time table lookups alongside strategies to improve instruction cache efficiency showcases the library's comprehensive approach to performance optimization.

Platform-specific implementations have been a focal point, with tailored optimizations for x86_64 platforms using Comb precomputation tables and hand-tuned assembly optimizations for ARM64 platforms, particularly benefiting newer Cortex cores. Efforts are also in place to support embedded systems, with current support for ESP32-S3 and planned enhancements for RISC-V architectures. The library, now in version 3.10.x, has successfully passed over 12,000 consistency tests on x86 and ARM64 platforms and offers full bindings for NPM and NuGet, facilitating easy integration into higher-level applications.

In pursuit of community engagement and peer review, the project's maintainer seeks feedback on several technical aspects including the integrity of constant-time operations, algorithm selection, and the elimination of branches in critical code paths to enhance security. The project’s GitHub repository and its technical changelog are available for review, contributing to the transparency and collaborative potential of this initiative. By inviting scrutiny and suggestions from the Delving Bitcoin community, the project underscores its commitment to security and performance within the cryptographic domain.