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zkInterface is a protocol for the interoperability of zero-knowledge frameworks.
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Aurélien Nicolas
Aurélien Nicolas Add programs print and example
Latest commit 698de06 Jul 12, 2019

ZK Gadget Standard Interface

zkInterface is a standard tool for zero-knowledge interoperability.

The spec can be found here.

How to contribute

  • In a frontend, implement a feature to export the circuits or gadgets to ZkInterface format.
  • In a proving system, support loading circuits from ZkInterface buffers or files.

See the implementation guide section in the spec above for more details, and check out the existing implementations below.


Proving System Export Circuits Import Circuits
Bellman (Groth16) Yes No Yes
Dalek (Bulletproofs) Yes No No
ZoKrates - Yes No
Libsnark PGHR Yes No

See also the WebAssembly modules and the live demo.

Structure of this repo

zkInterface.pdf The interface specification
zkinterface.fbs The gadget interface definition using FlatBuffers
rust/src/ Generated Rust code
rust/src/ Rust helpers to read messages
rust/src/ Rust helpers to write messages
rust/src/ Rust helpers to interact with C++
rust/src/ Example messages for a simple test circuit
cpp/zkinterface_generated.h Generated C++ code
cpp/gadget_example.cpp Example gadget in C++ Generate Rust and C++ code from zkinterface.fbs, and compile the C++ example
cpp/libsnark_integration.hpp Libsnark support
cpp/libsnark_example.cpp Libsnark gadget example


In the rust directory:

cargo test

This will generate and compile Rust and C++ code, and run a test of both sides communicating through the standard interface.

cargo run --bin example > example.zkif
cargo run --bin print   < example.zkif

This will generate and print a file containing the messages Circuit, R1CSConstraints, and Witness for a toy circuit.

Generated code

Generated C++ and Rust code is included.

For other languages, install the FlatBuffers code generator (flatc). One way is to compile it with the following:

git clone
cd flatbuffers
cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release

Then run: flatc --LANGUAGE zkinterface.fbs

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