I've built a comprehensive secp256k1 library in C++20 with zero external dependencies. Everything — SHA-256, SHA-512, Keccak-256, RIPEMD-160, Base58, Bech32 — is implemented from scratch.
Key highlights:
Assembly backends for x64 (MASM/GAS, BMI2/ADX), ARM64, RISC-V
SIMD: AVX2/AVX-512 batch operations
GPU: CUDA (4.63M kG/s), OpenCL, ROCm/HIP
Constant-time layer with separate namespace (no runtime flag switching)
Full protocol stack: ECDSA, Schnorr BIP-340, MuSig2, FROST, Adaptor sigs, Pedersen commitments
Complete Bitcoin support: Taproot, Silent Payments, BIP-32/44, all address types
27+ cryptocurrency address generation with auto-dispatch
Custom generator/curve context support
Runs on: x64, ARM64, RISC-V, ESP32, STM32, WASM, iOS, Android
200+ tests, fuzz harnesses
Design philosophy: hot paths are allocation-free, branchless where possible, with explicit buffers and fixed-size POD types. No exceptions/RTTI/virtual calls in compute paths
