Advanced

The world of Circom is vast, and here we take a look at some more advanced concepts.

Alternative Provers

SnarkJS is not the only option to prove Circom circuits, you can check out some alternative provers in other languages as well:

• Go-Rapidsnark is a collection of Go packages by Iden3, that allow you to compute witnesses, generate, or verify Circom proofs.
• Ark-Circom has Arkworks bindings to Circom's R1CS for proof & witness generation.
• Lambdaworks has Circom adapters for Groth16.

However, these are not as capable as SnarkJS, e.g. they only support Groth16 protocol.

Large Circuits

If you have very large circuits (e.g. >20M constraints) you will have some practical problems, most notably the limited memory of your machine. There is a great HackMD post that describes what the best practices are for large circuits, see here.

Folding

Folding is when a "well-structured" circuit with many iterations is folded into a single "iteration" from which a proof is generated that proves all iterations are correct. See more at awesome-folding.

• A recent work from PSE called Sonobe paves the way to fold Circom circuits.

• Nova-Scotia is a middleware to compile Circom circuits for the Nova prover.

Just Logging

If you would like to experiment with some circuit code quickly, zkRepl is usually the best option. In any case, if you still want to play locally you can simply write logs in your code and compile your circuit with:

circom ./your-circuit.circom --verbose

This will not emit any build artifacts, it will only print logs.