@crisp-e3/zk-inputs

WASM bindings for generating CRISP ZK proof inputs, compiled from Rust and shared between the server-side Node.js environment and the browser. This package lets the CRISP SDK produce the circuit witness data needed for Noir-based vote-validity proofs without duplicating the logic in TypeScript.

What it generates

The WASM module wraps a ZKInputsGenerator class that performs BFV encryption and produces the witness data needed for CRISP's Noir circuits.

generateInputs is the only entry point, and it covers all three operations: a first vote, a re-vote, and a masker contribution under the vote masking scheme that provides receipt-freeness.

generateInputs(previousCiphertext, publicKey, vote, keepPrevious)

• previousCiphertext is the ciphertext currently in the slot, or undefined when it is empty.
• keepPrevious is set only for a mask over an occupied slot. It makes the ballot add to that ciphertext; everything else replaces it.

One function rather than one per operation, deliberately: the encryption, the witness, and the published ciphertext have the same shape in every case, so nothing about a submission says which operation it was. Splitting the paths would make the three tellable apart, which is the attack masking exists to prevent.

The generator also exposes encryptVote / decryptVote for standalone BFV operations and generateKeys for key generation.

These witness objects are then passed to @noir-lang/noir_js and @aztec/bb.js to generate the actual ZK proofs.

Usage

This package requires a universal init pattern because:

• In Node.js (>=18) WASM can be loaded synchronously — no preloading needed.
• In the browser the WASM binary must be fetched and instantiated asynchronously.

The init subpackage handles both environments transparently.

❌ Don't use the default export

// Bad — the raw default loader doesn't work in Node.js contexts
import init, { ZKInputsGenerator } from '@crisp-e3/zk-inputs'

✅ Use the universal subpackage loader

import init from '@crisp-e3/zk-inputs/init'
import { ZKInputsGenerator } from '@crisp-e3/zk-inputs'

await init()
const generator = ZKInputsGenerator.withDefaults()
const { encryptedVote, inputs } = generator.generateInputs(
  previousCiphertext,
  publicKey,
  vote,
  keepPrevious,
)

Call init() once before using any other imports from @crisp-e3/zk-inputs. In browser environments init() fetches the WASM binary; in Node.js it is a no-op.

Building

The WASM bundle is compiled from the Rust source in crates/crisp-zk-inputs using wasm-pack:

# From the CRISP root
pnpm build:wasm