Add Poseidon circomlib compatibility tests

README.md

@@ -44,6 +44,14 @@ If you clone or link this repo as `opencircom` in your project root, compile wit
 circom your.circom --r1cs --wasm -o build -l opencircom/circuits
 ```
 
+## Compatibility
+
+Poseidon compatibility with circomlib is covered by `test/poseidon_compat_test.js`.
+The suite compares opencircom and circomlib wrapper circuits for `nInputs = 1, 2, 4, 16`
+against fixed witness vectors. `circomlib` is a dev-only test dependency; the published
+opencircom circuits remain dependency-free. No intentional Poseidon output differences
+are documented.
+
 ## Include in Hardhat or Foundry
 
 ### Install

package.json

@@ -25,6 +25,7 @@
   "devDependencies": {
     "chai": "^4.3.10",
     "circom_tester": "^0.0.21",
+    "circomlib": "^2.0.5",
     "mocha": "^10.7.3",
     "snarkjs": "^0.7.5"
   }

test/circuits/poseidon16_test.circom

@@ -0,0 +1,15 @@
+pragma circom 2.0.0;
+
+include "../../circuits/hashing/poseidon.circom";
+
+template Poseidon16Test() {
+    signal input in[16];
+    signal output out;
+    component p = Poseidon(16);
+    for (var i = 0; i < 16; i++) {
+        p.inputs[i] <== in[i];
+    }
+    out <== p.out;
+}
+
+component main = Poseidon16Test();

test/circuits/poseidon1_test.circom

@@ -0,0 +1,13 @@
+pragma circom 2.0.0;
+
+include "../../circuits/hashing/poseidon.circom";
+
+template Poseidon1Test() {
+    signal input in[1];
+    signal output out;
+    component p = Poseidon(1);
+    p.inputs[0] <== in[0];
+    out <== p.out;
+}
+
+component main = Poseidon1Test();

test/circuits/poseidon_circomlib_16_test.circom

@@ -0,0 +1,15 @@
+pragma circom 2.0.0;
+
+include "../../node_modules/circomlib/circuits/poseidon.circom";
+
+template CircomlibPoseidon16Test() {
+    signal input in[16];
+    signal output out;
+    component p = Poseidon(16);
+    for (var i = 0; i < 16; i++) {
+        p.inputs[i] <== in[i];
+    }
+    out <== p.out;
+}
+
+component main = CircomlibPoseidon16Test();

test/circuits/poseidon_circomlib_1_test.circom

@@ -0,0 +1,13 @@
+pragma circom 2.0.0;
+
+include "../../node_modules/circomlib/circuits/poseidon.circom";
+
+template CircomlibPoseidon1Test() {
+    signal input in[1];
+    signal output out;
+    component p = Poseidon(1);
+    p.inputs[0] <== in[0];
+    out <== p.out;
+}
+
+component main = CircomlibPoseidon1Test();

test/circuits/poseidon_circomlib_2_test.circom

@@ -0,0 +1,15 @@
+pragma circom 2.0.0;
+
+include "../../node_modules/circomlib/circuits/poseidon.circom";
+
+template CircomlibPoseidon2Test() {
+    signal input in[2];
+    signal output out;
+    component p = Poseidon(2);
+    for (var i = 0; i < 2; i++) {
+        p.inputs[i] <== in[i];
+    }
+    out <== p.out;
+}
+
+component main = CircomlibPoseidon2Test();

test/circuits/poseidon_circomlib_4_test.circom

@@ -0,0 +1,15 @@
+pragma circom 2.0.0;
+
+include "../../node_modules/circomlib/circuits/poseidon.circom";
+
+template CircomlibPoseidon4Test() {
+    signal input in[4];
+    signal output out;
+    component p = Poseidon(4);
+    for (var i = 0; i < 4; i++) {
+        p.inputs[i] <== in[i];
+    }
+    out <== p.out;
+}
+
+component main = CircomlibPoseidon4Test();

test/poseidon_compat_test.js

@@ -0,0 +1,65 @@
+const chai = require("chai");
+const path = require("path");
+const wasm_tester = require("circom_tester").wasm;
+
+const assert = chai.assert;
+
+const OPEN_CIRCUITS = {
+    1: "poseidon1_test.circom",
+    2: "poseidon2_test.circom",
+    4: "poseidon4_test.circom",
+    16: "poseidon16_test.circom",
+};
+
+const CIRCOMLIB_CIRCUITS = {
+    1: "poseidon_circomlib_1_test.circom",
+    2: "poseidon_circomlib_2_test.circom",
+    4: "poseidon_circomlib_4_test.circom",
+    16: "poseidon_circomlib_16_test.circom",
+};
+
+function vectorSet(width) {
+    return [
+        Array(width).fill(0),
+        Array.from({ length: width }, (_, i) => i + 1),
+        Array.from({ length: width }, (_, i) => String((i + 1) * 17)),
+    ];
+}
+
+describe("Poseidon compatibility with circomlib", function () {
+    const circuits = {};
+    this.timeout(120000);
+
+    before(async () => {
+        for (const width of Object.keys(OPEN_CIRCUITS)) {
+            circuits[width] = {
+                opencircom: await wasm_tester(path.join(__dirname, "circuits", OPEN_CIRCUITS[width]), {
+                    output: path.join(__dirname, "..", "build"),
+                    recompile: false,
+                }),
+                circomlib: await wasm_tester(path.join(__dirname, "circuits", CIRCOMLIB_CIRCUITS[width]), {
+                    output: path.join(__dirname, "..", "build"),
+                    recompile: false,
+                }),
+            };
+        }
+    });
+
+    for (const width of [1, 2, 4, 16]) {
+        it(`matches circomlib Poseidon(${width}) reference outputs`, async () => {
+            for (const inputs of vectorSet(width)) {
+                const opencircomWitness = await circuits[width].opencircom.calculateWitness({ in: inputs }, true);
+                const circomlibWitness = await circuits[width].circomlib.calculateWitness({ in: inputs }, true);
+
+                await circuits[width].opencircom.checkConstraints(opencircomWitness);
+                await circuits[width].circomlib.checkConstraints(circomlibWitness);
+
+                assert.equal(
+                    opencircomWitness[1].toString(),
+                    circomlibWitness[1].toString(),
+                    `Poseidon(${width}) mismatch for ${JSON.stringify(inputs)}`
+                );
+            }
+        });
+    }
+});