android-bpc

A small Android library that simultaneously contains an Android-build of the PBC library and the JPBC library, enabling fast computations on elliptic curves and pairings on Android.

The library is essentially a thin wrapper around the following three native libraries.

• jpbc-pbc is the PBC library itself, built using nkd-build.
• gmp is the GNU Multiple Precision Arithmetic Library; used by PBC for its calculations.
• jnidispatch comes from JNA and is the .so file contained in this file.

For each of these builds are included for the ARM and ARMv7 platforms.

Usage

Assuming you use gradle, perform the following steps:

1. git clone this repository somewhere, cd to it and run ./gradlew install.
2. Add compile "net.sietseringers:android-pbc:0.1" to the dependencies of your app.
3. Put the line

net.sietseringers.androidpbc.AndroidPBC.Initialize();

somewhere before you use any of the functionality of JPBC in Java.

After this, you can use the entire API that JPBC provides in the it.unisa.dia.gas namespace, including the part that refers to the PBC wrapper. Whenever you do, the included native library is used. For example, you can create a asymmetric (Type 3) bilinear pairing (called 'Type D' by the PBC documentation) as follows:

import it.unisa.dia.gas.plaf.jpbc.pbc.PBCPairingFactory;
import it.unisa.dia.gas.plaf.jpbc.pbc.curve.PBCTypeDCurveGenerator;
import it.unisa.dia.gas.jpbc.PairingParameters;

Pairing e = PBCPairingFactory.getPairing(new PBCTypeDCurveGenerator(9563).generate());

(Note that generating the curve parameters takes much longer than instantiating the pairing (which takes only ~ 0.5 seconds), so you should probably store and reuse the parameters that the PBCTypeDCurveGenerator constructor outputs.)

Warning

I cannot guarantee that this software will work. I have run just a few tests on only my own Android device. It works fine under those circumstances but more testing is certainly needed, so use with care.

Rebuilding GMP and PBC

The upper two libraries have been included as submodules in the jni/ folder. Assuming you have the Android NDK installed, they can be compiled as follows:

./gradlew ndkBuild

This will place them in the libs/ folder, after which they will be included in the final .aar file. For some reason this process also deletes the libjnidispatch.so files from the libs/ folder, you'll have to checkout those again.