libff
C++ library for Finite Fields and Elliptic Curves
libff is a C++ library for finite fields and elliptic curves. The library is developed by SCIPR Lab and contributors (see AUTHORS file) and is released under the MIT License (see LICENSE file).
Table of contents
Directory structure
The directory structure is as follows:
Elliptic curve choices
The libsnark library currently provides three options:
-
edwards
: an instantiation based on an Edwards curve, providing 80 bits of security. -
bn128
: an instantiation based on a Barreto-Naehrig curve, providing 128 bits of security. The underlying curve implementation is [ate-pairing], which has incorporated our patch that changes the BN curve to one suitable for SNARK applications.-
This implementation uses dynamically-generated machine code for the curve arithmetic. Some modern systems disallow execution of code on the heap, and will thus block this implementation.
For example, on Fedora 20 at its default settings, you will get the error
zmInit ERR:can't protect
when running this code. To solve this, runsudo setsebool -P allow_execheap 1
to allow execution, or usemake CURVE=ALT_BN128
instead.
-
-
alt_bn128
: an alternative tobn128
, somewhat slower but avoids dynamic code generation.
Note that bn128
requires an x86-64 CPU while the other curve choices
should be architecture-independent.
Build guide
The library has the following dependencies:
The library has been tested on Linux, but it is compatible with Windows and MacOS.
Installation
On Ubuntu 14.04 LTS:
sudo apt-get install build-essential git libboost-all-dev cmake libgmp3-dev libssl-dev libprocps3-dev pkg-config libsodium-dev
On MacOS, all of the libraries from the previous section can be installed with brew
, except for libprocps
, which is turned off by default.
Fetch dependencies from their GitHub repos:
git submodule init && git submodule update
Compilation
To compile, starting at the project root directory, create the build directory and Makefile:
mkdir build && cd build
cmake ..
If you are on macOS, change the cmake command to be
cmake .. -DOPENSSL_ROOT_DIR=$(brew --prefix openssl)
Other build flags include:
Flag | Value | Description |
---|---|---|
MAKE_INSTALL_PREFIX | (your path) | Specifies the desired install location. |
CMAKE_BUILD_TYPE | Debug | Enables asserts. Note that tests now use gtest instead of asserts. |
WITH_PROCPS | ON | Enables libprocps , which is by default turned off since it is not supported on some systems such as MacOS. |
Then, to compile and install the library, run this within the build directory:
make
make install
This will install libff.a
into /install/path/lib
; so your application should be linked using -L/install/path/lib -lff
. It also installs the requisite headers into /install/path/include
; so your application should be compiled using -I/install/path/include
.
Testing
To build and execute the tests for this library, run:
make check
Code formatting and linting
To run clang-tidy on this library, specify the variable USE_CLANG_TIDY
(eg. cmake .. -D USE_CLANG_TIDY=ON
).
Then, run:
make clang-tidy
One can specify which clang-tidy checks to run and which files to run clang-tidy on using the .clang-tidy
file in the root directory of the project.
Profile
To compile the multi-exponentiation profiler in this library, run:
make profile
The resulting profiler is named multiexp_profile
and can be found in the libff
folder under the build directory.