DISCLAIMER: Lurk is an early research-stage language. Neither the cryptography nor the software has been audited, and there is currently no trusted setup for Groth16 circuits. Do not use Lurk in production environments or anywhere else that security is necessary.
Lurk is a statically scoped dialect of Lisp, influenced by Scheme and Common Lisp. A language specification and reference implementation focused on describing and developing the core language can be found in the lurk repo.
Lurk's distinguishing feature relative to most programming languages is that correct execution of Lurk programs can be directly proved using zk-SNARKs. The resulting proofs are succinct: they are relatively small, can be verified quickly, and they reveal only the information explicitly contained in the statement to be proved.
Lurk's distinguishing feature relative to most zk-SNARK authoring languages is that Lurk is Turing complete, so arbitrary computational claims can be made and proved (subject to resource limitations, obviously). Because Lurk is a Lisp, its code is simply Lurk data, and any Lurk data can be directly evaluated as a Lurk program. Lurk constructs compound data using SNARK-friendly Poseidon hashes (provided by Neptune), so its data is naturally content-addressable.
Integration with backend proving systems and tooling for proof generation are both still very early. Performance and user experience are poor, but simple examples can be found in the fcomm example directory.
- The
fcommexample uses Groth16/SnarkPack+ to generate succinct (but somewhat large) proofs, using Bls12-381. - The forthcoming Nova backend will use the Nova proving system and the Pasta Curves.
- Future work may target Halo2 or other proving systems.
It is an explicit design goal that statements about the evaluation of Lurk programs have identical semantic meaning across backends, with the qualification that Lurk language instances are themselves parameterized on scalar field and hash function. When backends use the same scalar field and hash function, equivalent proofs can be generated across backends. This is because the concrete representation of content-addressed data is fixed.
Lurk backend integration is still immature, so current performance is not representative. As a rough approximation, we estimate that for entirely general computation using Lurk's universal circuit, Nova proving throughput will be on the order of 1,000 iterations per second per GPU. We expect that most compute-heavy applications will use optimized 'coprocessor' circuits, which will dramatically improve performance. Planned improvements to Nova will allow for smaller inner circuits, further improving throughput -- and for full parallelization of reduction proofs.
Lurk source files used in tests are in the lurk-lib submodule. You must initialize and update submodules before test will pass:
git submodule update --init --recursive
cargo run --example repl
Or use the wrapper script:
bin/lurkrs
Set the environment variable LURK_FIELD to specify the scalar field of the Lurk language instance:
LURK_FIELD=PALLAS(default): scalar field of PallasLURK_FIELD=VESTA: scalar field of VestaLURK_FIELD=BLS12-381: scalar field of BLS12-381
➜ lurk-rs ✗ bin/lurkrs
Finished release [optimized] target(s) in 0.06s
Running `target/release/examples/repl`
Lurk REPL welcomes you.
> (let ((square (lambda (x) (* x x)))) (square 8))
[9 iterations] => 64
>
Or enable info log-level for a trace of reduction frames:
➜ lurk-rs ✗ RUST_LOG=info bin/lurkrs
Finished release [optimized] target(s) in 0.05s
Running `target/release/examples/repl`
Lurk REPL welcomes you.
> (let ((square (lambda (x) (* x x)))) (square 8))
INFO lurk::eval > Frame: 0
Expr: (LET ((SQUARE (LAMBDA (X) (* X X)))) (SQUARE 8))
Env: NIL
Cont: Outermost
INFO lurk::eval > Frame: 1
Expr: (LAMBDA (X) (* X X))
Env: NIL
Cont: Let{ var: SQUARE, body: (SQUARE 8), saved_env: NIL, continuation: Outermost }
INFO lurk::eval > Frame: 2
Expr: (SQUARE 8)
Env: ((SQUARE . <FUNCTION (X) . ((* X X))>))
Cont: Tail{ saved_env: NIL, continuation: Outermost }
INFO lurk::eval > Frame: 3
Expr: SQUARE
Env: ((SQUARE . <FUNCTION (X) . ((* X X))>))
Cont: Call{ unevaled_arg: 8, saved_env: ((SQUARE . <FUNCTION (X) . ((* X X))>)), continuation: Tail{ saved_env: NIL, continuation: Outermost } }
INFO lurk::eval > Frame: 4
Expr: 8
Env: ((SQUARE . <FUNCTION (X) . ((* X X))>))
Cont: Call2{ function: <FUNCTION (X) . ((* X X))>, saved_env: ((SQUARE . <FUNCTION (X) . ((* X X))>)), continuation: Tail{ saved_env: NIL, continuation: Outermost } }
INFO lurk::eval > Frame: 5
Expr: (* X X)
Env: ((X . 8))
Cont: Tail{ saved_env: NIL, continuation: Outermost }
INFO lurk::eval > Frame: 6
Expr: X
Env: ((X . 8))
Cont: Binop{ operator: Product, unevaled_args: (X), saved_env: ((X . 8)), continuation: Tail{ saved_env: NIL, continuation: Outermost } }
INFO lurk::eval > Frame: 7
Expr: X
Env: ((X . 8))
Cont: Binop2{ operator: Product, evaled_arg: 8, continuation: Tail{ saved_env: NIL, continuation: Outermost } }
INFO lurk::eval > Frame: 8
Expr: Thunk{ value: 64 => cont: Outermost}
Env: NIL
Cont: Dummy
INFO lurk::eval > Frame: 9
Expr: 64
Env: NIL
Cont: Terminal
[9 iterations] => 64
>
You can enter into a Nix shell with the appropriate dependencies for Lurk with
$ nix-shell
And then building with Cargo as usual:
$ cargo build
You can install the lurkrs binary on your machine with
$ cargo install --path .
MIT or Apache 2.0