This is a Java library for building circuits for preprocessing zk-SNARKs. The library uses libsnark as a backend (https://github.com/scipr-lab/libsnark), and can integrate circuits produced by the Pinocchio compiler (https://vc.codeplex.com/SourceControl/latest) when needed by the programmer. The code consists of two main parts:



For Ubuntu 14.04, the following can be done to install the above:

Note: Don't clone libsnark from https://github.com/scipr-lab/libsnark. Make sure to use the modified libsnark submodule within the jsnark cloned repo in the next section.

Verify the installed version by java -version. In case it is not 1.8 or later, try $ sudo update-java-alternatives -s java-8-oracle

jsnark Installation Instructions

The CMakeLists files were modified to produce the needed executable for the interface. The executable will appear under build/libsnark/jsnark_interface

Running and Testing JsnarkCircuitBuilder

To compile the JsnarkCircuitBuilder project via command line, from the jsnark directory:

$ cd JsnarkCircuitBuilder
$ mkdir -p bin
$ javac -d bin -cp /usr/share/java/junit4.jar:bcprov-jdk15on-159.jar  $(find ./src/* | grep ".java$")

The classpaths of junit4 and bcprov-jdk15on-159.jar may need to be adapted in case the jars are located elsewhere. The above command assumes that bcprov-jdk15on-159.jar was moved to the JsnarkCircuitBuilder directory.

Before running the following, make sure the PATH_TO_LIBSNARK_EXEC property in config.properties points to the path of the run_ppzksnark executable.

To run a simple example, the following command can be used

$ java -cp bin examples.generators.SimpleCircuitGenerator

To run one of the JUnit tests available:

$ java -cp bin:/usr/share/java/junit4.jar org.junit.runner.JUnitCore  examples.tests.hash.SHA256_Test

Some of the examples and tests will require bcprov-jdk15on-159.jar as well to be added to the classpath.

Note: An IDE, e.g. Eclipse, or possibly the ant tool can be used instead to build and run the Java project more conveniently.

Examples included

Simple Examples

Cryptographic Primtives

Several cryptographic gadgets spanning hashes, block ciphers, key exchange, public key encryption and signatures can be found in src/examples/gadgets. We list some notes regarding few gadgets below:

Writing Circuits using jsnark

To summarize the steps needed:

Running circuit outputs on libsnark

Given the .arith and the .in files, it's possible to use command line directly to run the jsnark-libsnark interface. You can use the executable interface run_ppzksnark that appears in jsnark/libsnark/build/libsnark/jsnark_interface to run the libsnark algorithms on the circuit. The executable currently allows to run the proof systems r1cs_ppzksnark (default) and r1cs_gg_ppzksnark implemented in libsnark. To run the first, the executable just takes two arguments: the arithmetic circuit file path, and a sample input file path. To run the r1cs_gg_ppzksnark proof system [Gro16], the first argument should be gg, followed by the arithmetic circuit file path, and the sample input file path.

Further Notes

The gadget library of jsnark shares some similarities with the C++ Gadget library of libsnark, but it has some options that could possibly help with writing optimized circuits quickly without specifying all the details. If the reader is familiar with the gadget libraries of libsnark, here are some key points to minimize confusion:

Running circuits compiled by Pinocchio on libsnark


The code is undergoing more testing and integration of other features. The future versions of this library will include more documentation, examples and optimizations.


This code is developed and maintained by Ahmed Kosba [email protected]. Please email for any questions.