UltrafastSecp256k1/android

UltrafastSecp256k1 -- Android Port

Full CPU port of UltrafastSecp256k1 for Android (ARM64, ARMv7, x86_64, x86).

Quick Build

# Set NDK path
export ANDROID_NDK_HOME=/path/to/android-ndk-r26c

# Build ARM64 (primary target)
./build_android.sh arm64-v8a

# Build all ABIs
./build_android.sh

Output

output/jniLibs/
+-- arm64-v8a/libsecp256k1_jni.so
+-- armeabi-v7a/libsecp256k1_jni.so
+-- x86_64/libsecp256k1_jni.so
+-- x86/libsecp256k1_jni.so

Usage (Kotlin)

import com.secp256k1.native.Secp256k1

// Initialize once
Secp256k1.init()

// Key generation (constant-time -- side-channel safe)
val pubkey = Secp256k1.ctScalarMulGenerator(privkeyBytes)

// ECDH (constant-time)
val secret = Secp256k1.ctEcdh(myPrivkey, theirPubkey)

// Fast operations (public data only)
val g = Secp256k1.getGenerator()
val sum = Secp256k1.pointAdd(p1, p2)

Project Structure

android/
+-- CMakeLists.txt          -- Android CMake build
+-- build_android.sh        -- Linux/macOS build script
+-- build_android.ps1       -- Windows build script
+-- jni/secp256k1_jni.cpp   -- JNI bridge (C++ <-> Java/Kotlin)
+-- kotlin/.../Secp256k1.kt -- Kotlin wrapper
+-- example/                -- Example Android app

See Android Guide for full documentation.

Benchmarks (RK3588, Cortex-A55/A76, ARM64 ASM)

Operation	Time
field_mul (a*b mod p)	85 ns
field_sqr (a^2 mod p)	66 ns
field_add (a+b mod p)	18 ns
field_sub (a-b mod p)	16 ns
field_inverse	2,621 ns
fast scalar_mul (k*G)	7.6 us
fast scalar_mul (k*P)	77.6 us
CT scalar_mul (k*G)	545 us
ECDH (full CT)	545 us

Backend: ARM64 inline assembly (MUL/UMULH). ~5x faster than generic C++.