circomlib/test/sign.js

const chai = require("chai");
const path = require("path");
const snarkjs = require("@tornado/snarkjs");
const compiler = require("circom");

const assert = chai.assert;

const bigInt = snarkjs.bigInt;

function print(circuit, w, s) {
    console.log(s + ": " + w[circuit.getSignalIdx(s)]);
}

function getBits(v, n) {
    const res = [];
    for (let i = 0; i < n; i++) {
        if (v.shr(i).isOdd()) {
            res.push(bigInt.one);
        } else {
            res.push(bigInt.zero);
        }
    }
    return res;
}

const q = bigInt("21888242871839275222246405745257275088548364400416034343698204186575808495617");

describe("Sign test", () => {
    let circuit;
    before(async () => {
        const cirDef = await compiler(path.join(__dirname, "circuits", "sign_test.circom"));

        circuit = new snarkjs.Circuit(cirDef);

        console.log("NConstrains: " + circuit.nConstraints);
    });

    it("Sign of 0", async () => {
        const inp = getBits(bigInt.zero, 254);
        const w = circuit.calculateWitness({ in: inp });

        assert(w[circuit.getSignalIdx("main.sign")].equals(bigInt(0)));
    });

    it("Sign of 3", async () => {
        const inp = getBits(bigInt(3), 254);
        const w = circuit.calculateWitness({ in: inp });

        assert(w[circuit.getSignalIdx("main.sign")].equals(bigInt(0)));
    });

    it("Sign of q/2", async () => {
        const inp = getBits(q.shr(bigInt.one), 254);
        const w = circuit.calculateWitness({ in: inp });

        assert(w[circuit.getSignalIdx("main.sign")].equals(bigInt(0)));
    });

    it("Sign of q/2+1", async () => {
        const inp = getBits(q.shr(bigInt.one).add(bigInt.one), 254);
        const w = circuit.calculateWitness({ in: inp });

        assert(w[circuit.getSignalIdx("main.sign")].equals(bigInt(1)));
    });

    it("Sign of q-1", async () => {
        const inp = getBits(q.sub(bigInt.one), 254);
        const w = circuit.calculateWitness({ in: inp });

        assert(w[circuit.getSignalIdx("main.sign")].equals(bigInt(1)));
    });

    it("Sign of q", async () => {
        const inp = getBits(q, 254);
        const w = circuit.calculateWitness({ in: inp });

        assert(w[circuit.getSignalIdx("main.sign")].equals(bigInt(1)));
    });

    it("Sign of all ones", async () => {
        const inp = getBits(bigInt(1).shl(254).sub(bigInt(1)), 254);
        const w = circuit.calculateWitness({ in: inp });

        assert(w[circuit.getSignalIdx("main.sign")].equals(bigInt(1)));
    });
});