SplitCommit

A portable C++14 implementation of the recent UC-secure additively homomorphic commitment scheme of [1]. The codebase builds heavily on the libOTe library for efficient oblivious transfer extension.

The library is written with efficiency in mind, while being flexible enough for various applications. Currently two message-sizes are supported, bit commitments and 128-bit commitments. More might be added in the future, but if you want/need to add this functionality let me know!

Performance

On a single Intel Xeon server (2 36-cores Intel Xeon CPU E5-2699 v3 @ 2.30GHz and 256GB of RAM), utilizing a single thread per party, the implementation can perform n=2²⁴ commitment in 11 seconds (0.65 microseconds/per), decommit in 5.4 seconds (0.32 microseconds/per), and batch-decommit in 4.6 seconds (0.27 microseconds/per).

Installation

The code has been tested to work on MacOS (10.12.1), Windows 10, and Ubuntu 16.04.

Requirements

• C++ compiler with C++14 support. The code has been successfully built with GCC 5.3.1, GCC 6.1 and CLANG 3.8 and Microsoft Visual Studio. The project is self-contained, meaning no external libraries are required.

Linux/macOS

To clone, build and test the code:

• git clone --recursive https://github.com/AarhusCrypto/SplitCommit
• cd SplitCommit
• ./cmake-release.sh
• ./build/release/TestSplitCommit

If all tests succeed you are good to go.

Windows

In powershell, clone, build and test the code:

• git clone --recursive https://github.com/AarhusCrypto/SplitCommit
• cd SplitCommit/libs/libOTe
• ./buildAll.ps1
• cd ../..
• splitcommit.sln

Note:

• gtest located at ./libs/googletest/gtest must be manually built. That is, open ./libs/googletest/gtest/msvc/gtest.vcproj, upgrade it if needed, and then build it with Visual Studio.
• If you have issue with buildAll.ps1 which builds boost, miracl and libOTe, then follow the more manual instructions at libOTe which is what buildAll.ps1 automates.

Run the test-split-commit project to perform the unit tests.

Running the main files

Two main files are produced during compilation, build/release/SplitCommitSender and build/release/SplitCommitReceiver. An example run of the two clients on different machines could be

• [Machine A] ./build/release/SplitCommitSender -n 10000 -e 8 -ip [A's IP] -p [port_num]
• [Machine B] ./build/release/SplitCommitReceiver -n 10000 -e 8 -ip [A's IP] -p [port_num]

The above code prints the time it takes to respectively perform OTs, commit, decommit and batch decommit for 10,000 random values. The -e parameters specifies how many parallel executions to run. No matter the number of parallel executions, the code only runs num_cpus executions concurrently.

White Paper

We provide the following white paper including tutorial, brief description of the commitment scheme, insights on implementation details and more.

Acknowledgements

• A huge thanks goes out to Peter Rindal for helping with the integration with libOTe and optimizing performance of the library.
• The author also heartedly thanks Ignacio Cascudo Pueyo and Diego Ruano of Aalborg University for their invaluable help in creating the generator matrix for the [262,128,40] error correcting code used by the library.

References

• [1] T. K. Frederiksen, T. P. Jakobsen, J. B. Nielsen, R. Trifiletti, “On the Complexity of Additively Homomorphic UC commitments,” in TCC 2016-A, Part I, ser. LNCS, E. Kushilevitz and T. Malkin, Eds., vol. 9562. Springer, Jan. 2016, pp. 542–565. Availible: http://ia.cr/2015/694.