Circom 2 + Remix IDE Zero-Knowledge Circuits

This skill covers the full loop of building zero-knowledge circuits with circom 2, entirely inside Remix IDE (remix.ethereum.org), using its bundled circuit-compiler plugin (backed by circom_wasm) and the Remix terminal's built-in Node-like script runner, which has snarkjs, circomlibjs, and ethers available via require(...).

Do not assume a local Node/circom CLI environment unless the user says so — default to the Remix-native workflow described here, because remix.call(...) and the in-browser circuit-compiler plugin are how compilation and file I/O actually happen in Remix (there is no local filesystem or child_process).

The four things this skill produces

1. Circuits — .circom files with correct signal/template/constraint syntax.
2. Trusted setup scripts — Remix scripts that run Groth16's circuit-specific setup (snarkjs.zKey.*) from a .r1cs and a Powers-of-Tau file, producing a zkey and verification_key.json.
3. Proof generation scripts — Remix scripts that compute a witness, generate a Groth16 proof, verify it off-chain, and export a Solidity verifier contract + calldata.
4. Verification — either the off-chain snarkjs.groth16.verify call, or the exported Solidity verifier deployed and called via ethers in a Remix script.

Read references/circom-language.md before writing or editing any .circom file — it has the exact assignment operator semantics (<== vs <--), public/private signal rules, and control-flow constraints that are easy to get subtly wrong and that silently produce insecure circuits (under-constrained signals) rather than compile errors.

Read references/remix-workflow.md before writing any Remix script (setup, witness, proof, or verifier deployment) — it covers the Remix project file layout, the exact remix.call('circuit-compiler', ...) and remix.call('fileManager', ...) calls available, where Powers-of-Tau files come from, and common failure modes specific to running snarkjs in the browser (memory limits, type: "mem" vs file-based keys, BigInt/JSON serialization of signals).

Workflow