test(poseidon): add compatbility tests

Cherry-picked from #98

Co-authored by: =?UTF-8?q?Antonio=20Mej=C3=ADas=20Gil?= <anmegi.95@gmail.com>

halo2-base/Cargo.toml

@@ -38,6 +38,8 @@ criterion = "0.4"
 criterion-macro = "0.4"
 test-case = "3.1.0"
 proptest = "1.1.0"
+# native poseidon for testing
+pse-poseidon = { git = "https://github.com/axiom-crypto/pse-poseidon.git" }
 
 # memory allocation
 [target.'cfg(not(target_env = "msvc"))'.dependencies]

halo2-base/src/poseidon/tests/compatibility.rs

@@ -0,0 +1,117 @@
+use std::{cmp::max, iter::zip};
+
+use crate::{
+    gates::{builder::GateThreadBuilder, GateChip},
+    halo2_proofs::halo2curves::bn256::Fr,
+    poseidon::PoseidonHasherChip,
+    utils::ScalarField,
+};
+use pse_poseidon::Poseidon;
+use rand::Rng;
+
+// make interleaved calls to absorb and squeeze elements and
+// check that the result is the same in-circuit and natively
+fn poseidon_compatiblity_verification<
+    F: ScalarField,
+    const T: usize,
+    const RATE: usize,
+    const R_F: usize,
+    const R_P: usize,
+>(
+    // elements of F to absorb; one sublist = one absorption
+    mut absorptions: Vec<Vec<F>>,
+    // list of amounts of elements of F that should be squeezed every time
+    mut squeezings: Vec<usize>,
+) {
+    let mut builder = GateThreadBuilder::prover();
+    let gate = GateChip::default();
+
+    let ctx = builder.main(0);
+
+    // constructing native and in-circuit Poseidon sponges
+    let mut native_sponge = Poseidon::<F, T, RATE>::new(R_F, R_P);
+    // assuming SECURE_MDS = 0
+    let mut circuit_sponge = PoseidonHasherChip::<F, T, RATE>::new::<R_F, R_P, 0>(ctx);
+
+    // preparing to interleave absorptions and squeezings
+    let n_iterations = max(absorptions.len(), squeezings.len());
+    absorptions.resize(n_iterations, Vec::new());
+    squeezings.resize(n_iterations, 0);
+
+    for (absorption, squeezing) in zip(absorptions, squeezings) {
+        // absorb (if any elements were provided)
+        native_sponge.update(&absorption);
+        circuit_sponge.update(&ctx.assign_witnesses(absorption));
+
+        // squeeze (if any elements were requested)
+        for _ in 0..squeezing {
+            let native_squeezed = native_sponge.squeeze();
+            let circuit_squeezed = circuit_sponge.squeeze(ctx, &gate);
+
+            assert_eq!(native_squeezed, *circuit_squeezed.value());
+        }
+    }
+
+    // even if no squeezings were requested, we squeeze to verify the
+    // states are the same after all absorptions
+    let native_squeezed = native_sponge.squeeze();
+    let circuit_squeezed = circuit_sponge.squeeze(ctx, &gate);
+
+    assert_eq!(native_squeezed, *circuit_squeezed.value());
+}
+
+fn random_nested_list_f<F: ScalarField>(len: usize, max_sub_len: usize) -> Vec<Vec<F>> {
+    let mut rng = rand::thread_rng();
+    let mut list = Vec::new();
+    for _ in 0..len {
+        let len = rng.gen_range(0..=max_sub_len);
+        let mut sublist = Vec::new();
+
+        for _ in 0..len {
+            sublist.push(F::random(&mut rng));
+        }
+        list.push(sublist);
+    }
+    list
+}
+
+fn random_list_usize(len: usize, max: usize) -> Vec<usize> {
+    let mut rng = rand::thread_rng();
+    let mut list = Vec::new();
+    for _ in 0..len {
+        list.push(rng.gen_range(0..=max));
+    }
+    list
+}
+
+#[test]
+fn test_poseidon_compatibility_squeezing_only() {
+    let absorptions = Vec::new();
+    let squeezings = random_list_usize(10, 7);
+
+    poseidon_compatiblity_verification::<Fr, 3, 2, 8, 57>(absorptions, squeezings);
+}
+
+#[test]
+fn test_poseidon_compatibility_absorbing_only() {
+    let absorptions = random_nested_list_f(8, 5);
+    let squeezings = Vec::new();
+
+    poseidon_compatiblity_verification::<Fr, 3, 2, 8, 57>(absorptions, squeezings);
+}
+
+#[test]
+fn test_poseidon_compatibility_interleaved() {
+    let absorptions = random_nested_list_f(10, 5);
+    let squeezings = random_list_usize(7, 10);
+
+    poseidon_compatiblity_verification::<Fr, 3, 2, 8, 57>(absorptions, squeezings);
+}
+
+#[test]
+fn test_poseidon_compatibility_other_params() {
+    let absorptions = random_nested_list_f(10, 10);
+    let squeezings = random_list_usize(10, 10);
+
+    poseidon_compatiblity_verification::<Fr, 5, 4, 8, 120>(absorptions, squeezings);
+}

halo2-base/src/poseidon/tests/mod.rs

@@ -6,6 +6,8 @@ use crate::{
 
 use itertools::Itertools;
 
+mod compatibility;
+
 #[test]
 fn test_mds() {
     let spec = OptimizedPoseidonSpec::<Fr, 3, 2>::new::<8, 57, 0>();