bellpepper is a crate for building zk-SNARK circuits. It provides circuit traits and and primitive structures, as well as basic gadget implementations such as booleans and number abstractions.

Example circuit

Say we want to write a circuit that proves we know the preimage to some hash computed using SHA-256d (calling SHA-256 twice). The preimage must have a fixed length known in advance (because the circuit parameters will depend on it), but can otherwise have any value. We take the following strategy:

• Witness each bit of the preimage.
• Compute hash = SHA-256d(preimage) inside the circuit.
• Expose hash as a public input using multiscalar packing.

This crate exposes the main traits and core structures of the bellpepper library.