fix(plonky2): Improve verify slot is in range function

beacon-light-client/plonky2/circuits/src/build_final_circuit.rs

@@ -271,29 +271,16 @@ fn setup_commitment_mapper_targets(
     )
 }
 
-// TODO: test
 fn verify_slot_is_in_range(
     builder: &mut CircuitBuilder<GoldilocksField, 2>,
     slot: &BigUintTarget,
     current_epoch: &BigUintTarget,
 ) -> () {
     let slots_per_epoch = builder.constant_biguint(&BigUint::from_u32(32).unwrap());
 
-    let current_slot_min = builder.mul_biguint(&current_epoch, &slots_per_epoch);
+    let slot_epoch = builder.div_biguint(slot, &slots_per_epoch);
 
-    let slots_to_add = builder.constant_biguint(&BigUint::from_u32(31).unwrap());
-
-    let current_slot_max = builder.add_biguint(&current_slot_min, &slots_to_add);
-
-    let cmp1 = builder.cmp_biguint(&current_slot_min, &slot);
-
-    let cmp2 = builder.cmp_biguint(&slot, &current_slot_max);
-
-    let slot_is_in_range = builder.and(cmp1, cmp2);
-
-    let _true = builder._true();
-
-    builder.connect(slot_is_in_range.target, _true.target);
+    builder.connect_biguint(&slot_epoch, current_epoch);
 }
 
 fn setup_proof_targets(
@@ -359,3 +346,119 @@ fn create_final_config() -> CircuitConfig {
         ..standard_recursion_config
     }
 }
+
+#[cfg(test)]
+mod test_verify_slot_is_in_range {
+    use num::{BigUint, FromPrimitive};
+    use plonky2::{
+        field::goldilocks_field::GoldilocksField,
+        iop::witness::PartialWitness,
+        plonk::{
+            circuit_builder::CircuitBuilder, circuit_data::CircuitConfig,
+            config::PoseidonGoldilocksConfig,
+        },
+    };
+
+    use crate::{
+        biguint::{CircuitBuilderBiguint, WitnessBigUint},
+        build_final_circuit::verify_slot_is_in_range,
+    };
+
+    #[test]
+    fn test_verify_slot_is_in_range() -> std::result::Result<(), anyhow::Error> {
+        const D: usize = 2;
+        type C = PoseidonGoldilocksConfig;
+        type F = GoldilocksField;
+
+        let mut pw = PartialWitness::new();
+
+        let mut builder = CircuitBuilder::<F, D>::new(CircuitConfig::standard_recursion_config());
+
+        let slot_target = builder.add_virtual_biguint_target(2);
+        let current_epoch = builder.add_virtual_biguint_target(2);
+
+        verify_slot_is_in_range(&mut builder, &slot_target, &current_epoch);
+
+        pw.set_biguint_target(&slot_target, &BigUint::from_u64(6953401).unwrap());
+        pw.set_biguint_target(&current_epoch, &BigUint::from_u64(217293).unwrap());
+
+        let data = builder.build::<C>();
+        let proof = data.prove(pw)?;
+
+        data.verify(proof)
+    }
+
+    #[test]
+    fn test_verify_slot_is_in_range_first_slot_in_epoch() -> std::result::Result<(), anyhow::Error>
+    {
+        const D: usize = 2;
+        type C = PoseidonGoldilocksConfig;
+        type F = GoldilocksField;
+
+        let mut pw = PartialWitness::new();
+
+        let mut builder = CircuitBuilder::<F, D>::new(CircuitConfig::standard_recursion_config());
+
+        let slot_target = builder.add_virtual_biguint_target(2);
+        let current_epoch = builder.add_virtual_biguint_target(2);
+
+        verify_slot_is_in_range(&mut builder, &slot_target, &current_epoch);
+
+        pw.set_biguint_target(&slot_target, &BigUint::from_u64(7314752).unwrap());
+        pw.set_biguint_target(&current_epoch, &BigUint::from_u64(228586).unwrap());
+
+        let data = builder.build::<C>();
+        let proof = data.prove(pw)?;
+
+        data.verify(proof)
+    }
+
+    #[test]
+    fn test_verify_slot_is_in_range_last_slot_in_epoch() -> std::result::Result<(), anyhow::Error> {
+        const D: usize = 2;
+        type C = PoseidonGoldilocksConfig;
+        type F = GoldilocksField;
+
+        let mut pw = PartialWitness::new();
+
+        let mut builder = CircuitBuilder::<F, D>::new(CircuitConfig::standard_recursion_config());
+
+        let slot_target = builder.add_virtual_biguint_target(2);
+        let current_epoch = builder.add_virtual_biguint_target(2);
+
+        verify_slot_is_in_range(&mut builder, &slot_target, &current_epoch);
+
+        pw.set_biguint_target(&slot_target, &BigUint::from_u64(7314751).unwrap());
+        pw.set_biguint_target(&current_epoch, &BigUint::from_u64(228585).unwrap());
+
+        let data = builder.build::<C>();
+        let proof = data.prove(pw)?;
+
+        data.verify(proof)
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_verify_slot_is_not_in_range() -> () {
+        const D: usize = 2;
+        type C = PoseidonGoldilocksConfig;
+        type F = GoldilocksField;
+
+        let mut pw = PartialWitness::new();
+
+        let mut builder = CircuitBuilder::<F, D>::new(CircuitConfig::standard_recursion_config());
+
+        let slot_target = builder.add_virtual_biguint_target(2);
+        let current_epoch = builder.add_virtual_biguint_target(2);
+
+        verify_slot_is_in_range(&mut builder, &slot_target, &current_epoch);
+
+        pw.set_biguint_target(&slot_target, &BigUint::from_u64(7314751).unwrap());
+        pw.set_biguint_target(&current_epoch, &BigUint::from_u64(228586).unwrap());
+
+        let data = builder.build::<C>();
+        let proof = data.prove(pw).unwrap();
+
+        data.verify(proof).unwrap();
+    }
+}