Support mixed depth container merkle proofs (#508)

* remove enabled flag from merkle tree proofs

* add small existence mpt proofs in MainPod

* refactor params, add small transition proofs

* complete

* fix edge case in vdset

* fix: use existence only proof for vdset

* use consistent order for aux table

src/backends/plonky2/basetypes.rs

@@ -51,7 +51,7 @@ use crate::{
         mainpod::cache_get_rec_main_pod_verifier_circuit_data,
         primitives::merkletree::MerkleClaimAndProof,
     },
-    middleware::{containers::Array, Hash, Params, RawValue, Result, Value},
+    middleware::{containers::Array, Hash, Params, RawValue, Result, Value, EMPTY_HASH},
 };
 
 pub static DEFAULT_VD_LIST: LazyLock<Vec<VerifierOnlyCircuitData>> = LazyLock::new(|| {
@@ -95,6 +95,12 @@ impl Eq for VDSet {}
 
 impl VDSet {
     fn new_from_vds_hashes(mut vds_hashes: Vec<Hash>) -> Self {
+        // If vds_hashes is empty we add an zero entry to be used as padding when verifying merkle
+        // proofs of inclusion in the vds set.  This zero entry can't be abused because no circuit
+        // exists with a vds_hash = 0.
+        if vds_hashes.is_empty() {
+            vds_hashes.push(EMPTY_HASH);
+        }
         // before using the hash values, sort them, so that each set of
         // verifier_datas gets the same VDSet root
         vds_hashes.sort();
@@ -150,6 +156,9 @@ impl VDSet {
             ))?
             .clone())
     }
+    pub fn get_vds_proof_0(&self) -> MerkleClaimAndProof {
+        self.proofs_map[&self.vds_hashes[0]].clone()
+    }
     /// Returns true if the `verifier_data_hash` is in the set
     pub fn contains(&self, verifier_data_hash: HashOut) -> bool {
         self.proofs_map

src/backends/plonky2/circuits/common.rs

@@ -30,7 +30,7 @@ use crate::{
         mainpod::{Operation, OperationArg, OperationAux, Statement},
         primitives::merkletree::{
             verify_merkle_proof_circuit, MerkleClaimAndProof, MerkleClaimAndProofTarget,
-            MerkleProof, MerkleTreeStateTransitionProofTarget,
+            MerkleProof, MerkleProofExistenceTarget, MerkleTreeStateTransitionProofTarget,
         },
     },
     middleware::{
@@ -725,7 +725,6 @@ impl CustomPredicateInBatchTarget {
         let mtp =
             MerkleClaimAndProofTarget::new_virtual(Params::max_depth_custom_batch_mt(), builder);
         let _true = builder._true();
-        builder.connect(_true.target, mtp.enabled.target);
         builder.connect(_true.target, mtp.existence.target);
         let zero = builder.constant(F(0));
         let key = ValueTarget {
@@ -763,7 +762,7 @@ impl CustomPredicateInBatchTarget {
             value: RawValue::from(hash_fields(&predicate.to_fields())),
             proof: mtp.clone(),
         };
-        self.mtp.set_targets(pw, true, &mtp_claim)?;
+        self.mtp.set_targets(pw, &mtp_claim)?;
         Ok(())
     }
 }
@@ -987,7 +986,6 @@ pub trait Flattenable {
 /// elsewhere.
 #[derive(Copy, Clone)]
 pub struct MerkleClaimTarget {
-    pub(crate) enabled: BoolTarget,
     pub(crate) root: HashOutTarget,
     pub(crate) key: ValueTarget,
     pub(crate) value: ValueTarget,
@@ -997,7 +995,6 @@ pub struct MerkleClaimTarget {
 impl From<MerkleClaimAndProofTarget> for MerkleClaimTarget {
     fn from(pf: MerkleClaimAndProofTarget) -> Self {
         Self {
-            enabled: pf.enabled,
             root: pf.root,
             key: pf.key,
             value: pf.value,
@@ -1006,12 +1003,25 @@ impl From<MerkleClaimAndProofTarget> for MerkleClaimTarget {
     }
 }
 
+impl MerkleClaimTarget {
+    pub fn from_proof_existence(
+        builder: &mut CircuitBuilder,
+        pf: MerkleProofExistenceTarget,
+    ) -> Self {
+        Self {
+            root: pf.root,
+            key: pf.key,
+            value: pf.value,
+            existence: builder._true(),
+        }
+    }
+}
+
 /// For the purpose of op verification, we need only look up the
 /// Merkle state transition claim rather than the Merkle state
 /// transition proof since it is verified elsewhere.
 #[derive(Copy, Clone)]
 pub struct MerkleTreeStateTransitionClaimTarget {
-    pub(crate) enabled: BoolTarget,
     pub(crate) op: Target,
     pub(crate) old_root: HashOutTarget,
     pub(crate) new_root: HashOutTarget,
@@ -1022,7 +1032,6 @@ pub struct MerkleTreeStateTransitionClaimTarget {
 impl From<MerkleTreeStateTransitionProofTarget> for MerkleTreeStateTransitionClaimTarget {
     fn from(pf: MerkleTreeStateTransitionProofTarget) -> Self {
         Self {
-            enabled: pf.enabled,
             op: pf.op,
             old_root: pf.old_root,
             new_root: pf.new_root,
@@ -1063,7 +1072,6 @@ impl Flattenable for ValueTarget {
 impl Flattenable for MerkleClaimTarget {
     fn flatten(&self) -> Vec<Target> {
         [
-            vec![self.enabled.target],
             self.root.elements.to_vec(),
             self.key.elements.to_vec(),
             self.value.elements.to_vec(),
@@ -1075,31 +1083,28 @@ impl Flattenable for MerkleClaimTarget {
     fn from_flattened(params: &Params, vs: &[Target]) -> Self {
         assert_eq!(vs.len(), Self::size(params));
         Self {
-            enabled: BoolTarget::new_unsafe(vs[0]),
+            root: HashOutTarget::from_vec(vs[0..NUM_HASH_OUT_ELTS].to_vec()),
-            root: HashOutTarget::from_vec(vs[1..1 + NUM_HASH_OUT_ELTS].to_vec()),
+            key: ValueTarget::from_slice(&vs[NUM_HASH_OUT_ELTS..NUM_HASH_OUT_ELTS + VALUE_SIZE]),
-            key: ValueTarget::from_slice(
-                &vs[1 + NUM_HASH_OUT_ELTS..1 + NUM_HASH_OUT_ELTS + VALUE_SIZE],
-            ),
             value: ValueTarget::from_slice(
-                &vs[1 + NUM_HASH_OUT_ELTS + VALUE_SIZE..1 + NUM_HASH_OUT_ELTS + 2 * VALUE_SIZE],
+                &vs[NUM_HASH_OUT_ELTS + VALUE_SIZE..NUM_HASH_OUT_ELTS + 2 * VALUE_SIZE],
             ),
-            existence: BoolTarget::new_unsafe(vs[1 + NUM_HASH_OUT_ELTS + 2 * VALUE_SIZE]),
+            existence: BoolTarget::new_unsafe(vs[NUM_HASH_OUT_ELTS + 2 * VALUE_SIZE]),
         }
     }
 
     fn size(params: &Params) -> usize {
-        2 + HashOutTarget::size(params) + 2 * ValueTarget::size(params)
+        HashOutTarget::size(params) + 2 * ValueTarget::size(params) + 1
     }
 }
 
 impl Flattenable for MerkleTreeStateTransitionClaimTarget {
     fn flatten(&self) -> Vec<Target> {
         [
-            vec![self.enabled.target, self.op],
             self.old_root.elements.to_vec(),
             self.new_root.elements.to_vec(),
             self.op_key.elements.to_vec(),
             self.op_value.elements.to_vec(),
+            vec![self.op],
         ]
         .concat()
     }
@@ -1107,24 +1112,22 @@ impl Flattenable for MerkleTreeStateTransitionClaimTarget {
     fn from_flattened(params: &Params, vs: &[Target]) -> Self {
         assert_eq!(vs.len(), Self::size(params));
         Self {
-            enabled: BoolTarget::new_unsafe(vs[0]),
+            old_root: HashOutTarget::from_vec(vs[0..NUM_HASH_OUT_ELTS].to_vec()),
-            op: vs[1],
-            old_root: HashOutTarget::from_vec(vs[2..2 + NUM_HASH_OUT_ELTS].to_vec()),
             new_root: HashOutTarget::from_vec(
-                vs[2 + NUM_HASH_OUT_ELTS..2 * (1 + NUM_HASH_OUT_ELTS)].to_vec(),
+                vs[NUM_HASH_OUT_ELTS..2 * NUM_HASH_OUT_ELTS].to_vec(),
             ),
             op_key: ValueTarget::from_slice(
-                &vs[2 * (1 + NUM_HASH_OUT_ELTS)..2 * (1 + NUM_HASH_OUT_ELTS) + VALUE_SIZE],
+                &vs[2 * NUM_HASH_OUT_ELTS..2 * NUM_HASH_OUT_ELTS + VALUE_SIZE],
             ),
             op_value: ValueTarget::from_slice(
-                &vs[2 * (1 + NUM_HASH_OUT_ELTS) + VALUE_SIZE
+                &vs[2 * NUM_HASH_OUT_ELTS + VALUE_SIZE..2 * NUM_HASH_OUT_ELTS + 2 * VALUE_SIZE],
-                    ..2 * (1 + NUM_HASH_OUT_ELTS) + 2 * VALUE_SIZE],
             ),
+            op: vs[2 * NUM_HASH_OUT_ELTS + 2 * VALUE_SIZE],
         }
     }
 
     fn size(params: &Params) -> usize {
-        2 * (1 + HashOutTarget::size(params)) + 2 * ValueTarget::size(params)
+        2 * HashOutTarget::size(params) + 2 * ValueTarget::size(params) + 1
     }
 }
 

src/backends/plonky2/mainpod/mod.rs

@@ -148,14 +148,20 @@ pub(crate) fn extract_custom_predicate_verifications(
     Ok(table)
 }
 
+#[derive(Default, Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct MerkleProofs {
+    pub(crate) medium: Vec<MerkleClaimAndProof>,
+    pub(crate) small: Vec<MerkleClaimAndProof>,
+}
+
 /// Extracts Merkle proofs from Contains/NotContains ops.
 pub(crate) fn extract_merkle_proofs(
     params: &Params,
     aux_list: &mut [OperationAux],
     operations: &[middleware::Operation],
     statements: &[middleware::Statement],
-) -> Result<Vec<MerkleClaimAndProof>> {
+) -> Result<MerkleProofs> {
-    let mut table = Vec::new();
+    let mut tables = MerkleProofs::default();
     for (i, (op, st)) in operations.iter().zip(statements.iter()).enumerate() {
         let deduction_err = || MiddlewareError::invalid_deduction(op.clone(), st.clone());
         let (root, key, value, pf) = match (op, st) {
@@ -178,31 +184,42 @@ pub(crate) fn extract_merkle_proofs(
             }
             _ => continue,
         };
-        aux_list[i] = OperationAux::MerkleProofIndex(table.len());
+        let claim_proof = MerkleClaimAndProof::new(Hash::from(root), key, value, pf.clone());
-        table.push(MerkleClaimAndProof::new(
+        if pf.existence
-            Hash::from(root),
+            // TODO: Make sure there's no off-by-one error here
-            key,
+            && pf.siblings.len() <= params.containers.max_depth_small
-            value,
+            && tables.small.len() < params.containers.state.max_small
-            pf.clone(),
+        {
-        ));
+            aux_list[i] = OperationAux::MerkleProofIndex(Size::Small, tables.small.len());
+            tables.small.push(claim_proof);
+        } else {
+            aux_list[i] = OperationAux::MerkleProofIndex(Size::Medium, tables.medium.len());
+            tables.medium.push(claim_proof);
         }
-    if table.len() > params.max_merkle_proofs_containers {
+    }
+    if tables.medium.len() > params.containers.state.max_medium {
         return Err(Error::custom(format!(
             "The number of required Merkle proofs ({}) exceeds the maximum number ({}).",
-            table.len(),
+            tables.medium.len(),
-            params.max_merkle_proofs_containers
+            params.containers.state.max_medium
         )));
     }
-    Ok(table)
+    Ok(tables)
+}
+
+#[derive(Default, Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct MerkleTransitionProofs {
+    pub(crate) medium: Vec<MerkleTreeStateTransitionProof>,
+    pub(crate) small: Vec<MerkleTreeStateTransitionProof>,
 }
 
 /// Extracts Merkle state transition proofs from container update ops.
-pub(crate) fn extract_merkle_tree_state_transition_proofs(
+pub(crate) fn extract_merkle_transition_proofs(
     params: &Params,
     aux_list: &mut [OperationAux],
     operations: &[middleware::Operation],
-) -> Result<Vec<MerkleTreeStateTransitionProof>> {
+) -> Result<MerkleTransitionProofs> {
-    let mut table = Vec::new();
+    let mut tables = MerkleTransitionProofs::default();
     for (i, op) in operations.iter().enumerate() {
         let pf = match op {
             middleware::Operation::ContainerInsertFromEntries(_, _, _, _, pf)
@@ -210,17 +227,27 @@ pub(crate) fn extract_merkle_tree_state_transition_proofs(
             | middleware::Operation::ContainerDeleteFromEntries(_, _, _, pf) => pf.clone(),
             _ => continue,
         };
-        aux_list[i] = OperationAux::MerkleTreeStateTransitionProofIndex(table.len());
+        if pf.op_proof.existence
-        table.push(pf);
+            // TODO: Make sure there's no off-by-one error here
+            && pf.siblings.len() <= params.containers.max_depth_small
+            && tables.small.len() < params.containers.transition.max_small
+        {
+            aux_list[i] = OperationAux::MerkleTransitionProofIndex(Size::Small, tables.small.len());
+            tables.small.push(pf);
+        } else {
+            aux_list[i] =
+                OperationAux::MerkleTransitionProofIndex(Size::Medium, tables.medium.len());
+            tables.medium.push(pf);
         }
-    if table.len() > params.max_merkle_tree_state_transition_proofs_containers {
+    }
+    if tables.medium.len() > params.containers.transition.max_medium {
         return Err(Error::custom(format!(
             "The number of required Merkle proofs ({}) exceeds the maximum number ({}).",
-            table.len(),
+            tables.medium.len(),
-            params.max_merkle_tree_state_transition_proofs_containers
+            params.containers.transition.max_medium
         )));
     }
-    Ok(table)
+    Ok(tables)
 }
 
 pub(crate) fn extract_public_key_of(
@@ -513,6 +540,8 @@ impl MainPodProver for Prover {
         let mut aux_list = vec![OperationAux::None; params.max_priv_statements()];
         let merkle_proofs =
             extract_merkle_proofs(params, &mut aux_list, inputs.operations, inputs.statements)?;
+        let merkle_transition_proofs =
+            extract_merkle_transition_proofs(params, &mut aux_list, inputs.operations)?;
         let custom_predicates = extract_custom_predicates(params, inputs.operations)?;
         let custom_predicate_verifications = extract_custom_predicate_verifications(
             params,
@@ -537,9 +566,6 @@ impl MainPodProver for Prover {
         let signed_bys =
             extract_signatures(params, &mut aux_list, inputs.operations, inputs.statements)?;
 
-        let merkle_tree_state_transition_proofs =
-            extract_merkle_tree_state_transition_proofs(params, &mut aux_list, inputs.operations)?;
-
         let (statements, public_statements) = layout_statements(params, false, &inputs)?;
         let operations = process_private_statements_operations(
             params,
@@ -572,20 +598,15 @@ impl MainPodProver for Prover {
             .collect_vec();
 
         let mut vd_mt_proofs = Vec::with_capacity(inputs.pods.len());
+        let pad_vd_mt_proof = inputs.vd_set.get_vds_proof_0();
         for (pod, vd) in inputs.pods.iter().zip(&verifier_datas) {
             vd_mt_proofs.push(if pod.is_main() {
-                (true, inputs.vd_set.get_vds_proof(vd)?)
+                inputs.vd_set.get_vds_proof(vd)?
             } else {
                 // For intro pods we don't verify inclusion of their vk into the vd set, so we
-                // generate a dummy mt proof with expected root and value to pass some constraints
+                // use a valid vds proof that matches the expected root but not the value to pass
-                (
+                // the constraints
-                    false,
+                pad_vd_mt_proof.clone()
-                    MerkleClaimAndProof {
-                        root: inputs.vd_set.root(),
-                        value: RawValue::from(pod.verifier_data_hash()),
-                        ..MerkleClaimAndProof::empty()
-                    },
-                )
             });
         }
 
@@ -598,7 +619,7 @@ impl MainPodProver for Prover {
             merkle_proofs,
             public_key_of_sks,
             signed_bys,
-            merkle_tree_state_transition_proofs,
+            merkle_transition_proofs,
             custom_predicates_with_mpt_proofs,
             custom_predicate_verifications,
         };
@@ -985,7 +1006,18 @@ pub mod tests {
             max_statements: 2,
             max_public_statements: 1,
             max_input_pods_public_statements: 0,
-            max_merkle_proofs_containers: 0,
+            containers: middleware::ParamsContainers {
+                state: middleware::ParamsMerkleProofs {
+                    max_small: 0,
+                    max_medium: 0,
+                },
+                transition: middleware::ParamsMerkleProofs {
+                    max_small: 0,
+                    max_medium: 0,
+                },
+                max_depth_small: 8,
+                max_depth_medium: 32,
+            },
             max_public_key_of: 0,
             max_custom_predicate_verifications: 0,
             max_custom_predicates: 0,
@@ -1024,11 +1056,20 @@ pub mod tests {
             max_custom_predicates: 2,
             max_custom_predicate_verifications: 2,
             max_custom_predicate_wildcards: 3,
-            max_merkle_proofs_containers: 2,
-            max_merkle_tree_state_transition_proofs_containers: 2,
             max_public_key_of: 2,
-            max_depth_mt_containers: 4,
             max_depth_mt_vds: 6,
+            containers: middleware::ParamsContainers {
+                state: middleware::ParamsMerkleProofs {
+                    max_small: 2,
+                    max_medium: 2,
+                },
+                transition: middleware::ParamsMerkleProofs {
+                    max_small: 2,
+                    max_medium: 2,
+                },
+                max_depth_small: 2,
+                max_depth_medium: 4,
+            },
         };
         let mut vds = DEFAULT_VD_LIST.clone();
         vds.push(rec_main_pod_circuit_data(&params).1.verifier_only.clone());
@@ -1087,8 +1128,18 @@ pub mod tests {
             max_public_statements: 4,
             max_custom_predicate_wildcards: 4,
             max_custom_predicate_verifications: 2,
-            max_merkle_proofs_containers: 3,
+            containers: middleware::ParamsContainers {
-            max_merkle_tree_state_transition_proofs_containers: 0,
+                state: middleware::ParamsMerkleProofs {
+                    max_small: 0,
+                    max_medium: 3,
+                },
+                transition: middleware::ParamsMerkleProofs {
+                    max_small: 0,
+                    max_medium: 0,
+                },
+                max_depth_small: 8,
+                max_depth_medium: 32,
+            },
             ..Default::default()
         };
         println!("{:#?}", params);
@@ -1156,8 +1207,18 @@ pub mod tests {
             max_public_statements: 2,
             max_custom_predicate_wildcards: 4,
             max_custom_predicate_verifications: 2,
-            max_merkle_proofs_containers: 0,
+            containers: middleware::ParamsContainers {
-            max_merkle_tree_state_transition_proofs_containers: 0,
+                state: middleware::ParamsMerkleProofs {
+                    max_small: 0,
+                    max_medium: 0,
+                },
+                transition: middleware::ParamsMerkleProofs {
+                    max_small: 0,
+                    max_medium: 0,
+                },
+                max_depth_small: 8,
+                max_depth_medium: 32,
+            },
             ..Default::default()
         };
         let mut vds = DEFAULT_VD_LIST.clone();

src/backends/plonky2/mainpod/operation.rs

@@ -5,8 +5,7 @@ use serde::{Deserialize, Serialize};
 use crate::{
     backends::plonky2::{
         error::{Error, Result},
-        mainpod::{SignedBy, Statement},
+        mainpod::{MerkleProofs, MerkleTransitionProofs, SignedBy, Statement},
-        primitives::merkletree::{MerkleClaimAndProof, MerkleTreeStateTransitionProof},
     },
     middleware::{self, OperationType, Params},
 };
@@ -30,50 +29,89 @@ impl OperationArg {
     }
 }
 
+#[derive(Clone, Copy, Debug, PartialEq, Serialize, Deserialize)]
+pub enum Size {
+    Small,
+    Medium,
+}
+
+impl fmt::Display for Size {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Self::Small => write!(f, "small"),
+            Self::Medium => write!(f, "medium"),
+        }
+    }
+}
+
+impl Size {
+    pub const fn min() -> Self {
+        Self::Small
+    }
+    pub const fn max() -> Self {
+        Self::Medium
+    }
+}
+
 #[derive(Clone, Copy, Debug, PartialEq, Serialize, Deserialize)]
 pub enum OperationAux {
     None,
-    MerkleProofIndex(usize),
+    MerkleProofIndex(Size, usize),
+    MerkleTransitionProofIndex(Size, usize),
     PublicKeyOfIndex(usize),
     SignedByIndex(usize),
-    MerkleTreeStateTransitionProofIndex(usize),
     CustomPredVerifyIndex(usize),
 }
 
 impl OperationAux {
-    fn table_offset_merkle_proof(_params: &Params) -> usize {
+    fn table_offset_merkle_proof(params: &Params, size: Size) -> usize {
+        match size {
             // At index 0 we store a zero entry
-        1
+            Size::Small => 1,
+            Size::Medium => {
+                Self::table_offset_merkle_proof(params, Size::Small)
+                    + params.containers.state.max_small
+            }
+        }
+    }
+    fn table_offset_merkle_transition_proof(params: &Params, size: Size) -> usize {
+        match size {
+            Size::Small => {
+                Self::table_offset_merkle_proof(params, Size::min())
+                    + params.containers.state.max_total()
+            }
+            Size::Medium => {
+                Self::table_offset_merkle_transition_proof(params, Size::Small)
+                    + params.containers.transition.max_small
+            }
+        }
+    }
+    fn table_offset_custom_pred_verify(params: &Params) -> usize {
+        Self::table_offset_merkle_transition_proof(params, Size::min())
+            + params.containers.transition.max_total()
     }
     fn table_offset_public_key_of(params: &Params) -> usize {
-        Self::table_offset_merkle_proof(params) + params.max_merkle_proofs_containers
+        Self::table_offset_custom_pred_verify(params) + params.max_custom_predicate_verifications
     }
     fn table_offset_signed_by(params: &Params) -> usize {
         Self::table_offset_public_key_of(params) + params.max_public_key_of
     }
-    fn table_offset_merkle_tree_state_transition_proof(params: &Params) -> usize {
-        Self::table_offset_signed_by(params) + params.max_signed_by
-    }
-    fn table_offset_custom_pred_verify(params: &Params) -> usize {
-        Self::table_offset_merkle_tree_state_transition_proof(params)
-            + params.max_merkle_tree_state_transition_proofs_containers
-    }
     pub(crate) fn table_size(params: &Params) -> usize {
-        1 + params.max_merkle_proofs_containers
+        1 + params.containers.state.max_total()
+            + params.containers.transition.max_total()
+            + params.max_custom_predicate_verifications
             + params.max_public_key_of
             + params.max_signed_by
-            + params.max_merkle_tree_state_transition_proofs_containers
-            + params.max_custom_predicate_verifications
     }
     pub fn table_index(&self, params: &Params) -> usize {
         match self {
             Self::None => 0,
-            Self::MerkleProofIndex(i) => Self::table_offset_merkle_proof(params) + *i,
+            Self::MerkleProofIndex(size, i) => Self::table_offset_merkle_proof(params, *size) + *i,
+            Self::MerkleTransitionProofIndex(size, i) => {
+                Self::table_offset_merkle_transition_proof(params, *size) + *i
+            }
             Self::PublicKeyOfIndex(i) => Self::table_offset_public_key_of(params) + *i,
             Self::SignedByIndex(i) => Self::table_offset_signed_by(params) + *i,
-            Self::MerkleTreeStateTransitionProofIndex(i) => {
-                Self::table_offset_merkle_tree_state_transition_proof(params) + *i
-            }
             Self::CustomPredVerifyIndex(i) => Self::table_offset_custom_pred_verify(params) + *i,
         }
     }
@@ -96,8 +134,8 @@ impl Operation {
         &self,
         statements: &[Statement],
         signatures: &[SignedBy],
-        merkle_proofs: &[MerkleClaimAndProof],
+        merkle_proofs: &MerkleProofs,
-        merkle_tree_state_transition_proofs: &[MerkleTreeStateTransitionProof],
+        merkle_transition_proofs: &MerkleTransitionProofs,
     ) -> Result<crate::middleware::Operation> {
         let deref_args = self
             .1
@@ -113,17 +151,26 @@ impl Operation {
             .collect::<Result<Vec<_>>>()?;
         let deref_aux = match self.2 {
             OperationAux::None => crate::middleware::OperationAux::None,
-            OperationAux::CustomPredVerifyIndex(_) => crate::middleware::OperationAux::None,
+            OperationAux::MerkleProofIndex(size, i) => {
-            OperationAux::MerkleProofIndex(i) => crate::middleware::OperationAux::MerkleProof(
+                let table = match size {
-                merkle_proofs
+                    Size::Small => &merkle_proofs.small,
+                    Size::Medium => &merkle_proofs.medium,
+                };
+                crate::middleware::OperationAux::MerkleProof(
+                    table
                         .get(i)
                         .ok_or(Error::custom(format!("Missing Merkle proof index {}", i)))?
                         .proof
                         .clone(),
-            ),
+                )
-            OperationAux::MerkleTreeStateTransitionProofIndex(i) => {
+            }
+            OperationAux::MerkleTransitionProofIndex(size, i) => {
+                let table = match size {
+                    Size::Small => &merkle_transition_proofs.small,
+                    Size::Medium => &merkle_transition_proofs.medium,
+                };
                 crate::middleware::OperationAux::MerkleTreeStateTransitionProof(
-                    merkle_tree_state_transition_proofs
+                    table
                         .get(i)
                         .ok_or(Error::custom(format!(
                             "Missing Merkle state transition proof index {}",
@@ -132,6 +179,7 @@ impl Operation {
                         .clone(),
                 )
             }
+            OperationAux::CustomPredVerifyIndex(_) => crate::middleware::OperationAux::None,
             OperationAux::SignedByIndex(i) => crate::middleware::OperationAux::Signature(
                 signatures
                     .get(i)
@@ -165,12 +213,14 @@ impl fmt::Display for Operation {
         }
         match self.2 {
             OperationAux::None => (),
-            OperationAux::MerkleProofIndex(i) => write!(f, " merkle_proof_{:02}", i)?,
+            OperationAux::MerkleProofIndex(size, i) => {
+                write!(f, " {}_merkle_proof_{:02}", size, i)?
+            }
             OperationAux::CustomPredVerifyIndex(i) => write!(f, " custom_pred_verify_{:02}", i)?,
             OperationAux::PublicKeyOfIndex(i) => write!(f, " public_key_of_{:02}", i)?,
             OperationAux::SignedByIndex(i) => write!(f, " signed_by_{:02}", i)?,
-            OperationAux::MerkleTreeStateTransitionProofIndex(i) => {
+            OperationAux::MerkleTransitionProofIndex(size, i) => {
-                write!(f, " merkle_tree_state_transition_proof_{:02}", i)?
+                write!(f, " {}_merkle_transition_proof_{:02}", size, i)?
             }
         }
         Ok(())

src/backends/plonky2/mock/mainpod.rs

@@ -11,13 +11,12 @@ use crate::{
         basetypes::{Proof, VerifierOnlyCircuitData},
         error::{Error, Result},
         mainpod::{
-            calculate_statements_hash, extract_merkle_proofs,
+            calculate_statements_hash, extract_merkle_proofs, extract_merkle_transition_proofs,
-            extract_merkle_tree_state_transition_proofs, extract_signatures, layout_statements,
+            extract_signatures, layout_statements, process_private_statements_operations,
-            process_private_statements_operations, process_public_statements_operations, Operation,
+            process_public_statements_operations, MerkleProofs, MerkleTransitionProofs, Operation,
             OperationAux, SignedBy, Statement,
         },
         mock::emptypod::MockEmptyPod,
-        primitives::merkletree::{MerkleClaimAndProof, MerkleTreeStateTransitionProof},
         recursion::hash_verifier_data,
     },
     middleware::{
@@ -45,10 +44,10 @@ pub struct MockMainPod {
     operations: Vec<Operation>,
     // public subset of the `statements` vector
     public_statements: Vec<Statement>,
-    // All Merkle proofs
+    // All Merkle proofs for containers
-    merkle_proofs_containers: Vec<MerkleClaimAndProof>,
+    merkle_proofs: MerkleProofs,
-    // All Merkle tree state transition proofs
+    // All Merkle tree state transition proofs for containers
-    merkle_tree_state_transition_proofs_containers: Vec<MerkleTreeStateTransitionProof>,
+    merkle_transition_proofs: MerkleTransitionProofs,
     // All verified signatures
     signatures: Vec<SignedBy>,
 }
@@ -124,8 +123,8 @@ struct Data {
     public_statements: Vec<Statement>,
     operations: Vec<Operation>,
     statements: Vec<Statement>,
-    merkle_proofs: Vec<MerkleClaimAndProof>,
+    merkle_proofs: MerkleProofs,
-    merkle_tree_state_transition_proofs: Vec<MerkleTreeStateTransitionProof>,
+    merkle_transition_proofs: MerkleTransitionProofs,
     signatures: Vec<SignedBy>,
     input_pods: Vec<(usize, Params, Hash, VDSet, serde_json::Value)>,
 }
@@ -153,8 +152,8 @@ impl MockMainPod {
         let merkle_proofs =
             extract_merkle_proofs(params, &mut aux_list, inputs.operations, inputs.statements)?;
         // Similarly for Merkle state transition proofs.
-        let merkle_tree_state_transition_proofs =
+        let merkle_transition_proofs =
-            extract_merkle_tree_state_transition_proofs(params, &mut aux_list, inputs.operations)?;
+            extract_merkle_transition_proofs(params, &mut aux_list, inputs.operations)?;
         let signatures =
             extract_signatures(params, &mut aux_list, inputs.operations, inputs.statements)?;
 
@@ -185,8 +184,8 @@ impl MockMainPod {
             public_statements,
             statements,
             operations,
-            merkle_proofs_containers: merkle_proofs,
+            merkle_proofs,
-            merkle_tree_state_transition_proofs_containers: merkle_tree_state_transition_proofs,
+            merkle_transition_proofs,
             signatures,
         })
     }
@@ -260,8 +259,8 @@ impl Pod for MockMainPod {
                     .deref(
                         &self.statements[..input_statement_offset + i],
                         &self.signatures,
-                        &self.merkle_proofs_containers,
+                        &self.merkle_proofs,
-                        &self.merkle_tree_state_transition_proofs_containers,
+                        &self.merkle_transition_proofs,
                     )?
                     .check_and_log(&self.params, &s.clone().try_into()?)
                     .map_err(|e| e.into())
@@ -321,10 +320,8 @@ impl Pod for MockMainPod {
             public_statements: self.public_statements.clone(),
             operations: self.operations.clone(),
             statements: self.statements.clone(),
-            merkle_proofs: self.merkle_proofs_containers.clone(),
+            merkle_proofs: self.merkle_proofs.clone(),
-            merkle_tree_state_transition_proofs: self
+            merkle_transition_proofs: self.merkle_transition_proofs.clone(),
-                .merkle_tree_state_transition_proofs_containers
-                .clone(),
             signatures: self.signatures.clone(),
             input_pods,
         })
@@ -344,7 +341,7 @@ impl Pod for MockMainPod {
             operations,
             statements,
             merkle_proofs,
-            merkle_tree_state_transition_proofs,
+            merkle_transition_proofs,
             signatures,
             input_pods,
         } = serde_json::from_value(data)?;
@@ -362,8 +359,8 @@ impl Pod for MockMainPod {
             public_statements,
             operations,
             statements,
-            merkle_proofs_containers: merkle_proofs,
+            merkle_proofs,
-            merkle_tree_state_transition_proofs_containers: merkle_tree_state_transition_proofs,
+            merkle_transition_proofs,
             signatures,
         })
     }

src/backends/plonky2/primitives/merkletree/circuit.rs

@@ -42,8 +42,6 @@ use crate::{
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct MerkleClaimAndProofTarget {
     pub(crate) max_depth: usize,
-    // `enabled` determines if the merkleproof verification is enabled
-    pub(crate) enabled: BoolTarget,
     pub(crate) root: HashOutTarget,
     pub(crate) key: ValueTarget,
     pub(crate) value: ValueTarget,
@@ -121,16 +119,9 @@ pub fn verify_merkle_proof_circuit(
     let obtained_root =
         compute_root_from_leaf(max_depth, builder, &path, &leaf_hash, &proof.siblings);
 
-    // check that obtained_root==root (from inputs), when enabled==true
+    // check that obtained_root==root (from inputs)
-    let zero = builder.zero();
-    let expected_root: Vec<Target> = (0..HASH_SIZE)
-        .map(|j| builder.select(proof.enabled, proof.root.elements[j], zero))
-        .collect();
-    let computed_root: Vec<Target> = (0..HASH_SIZE)
-        .map(|j| builder.select(proof.enabled, obtained_root.elements[j], zero))
-        .collect();
     for j in 0..HASH_SIZE {
-        builder.connect(computed_root[j], expected_root[j]);
+        builder.connect(obtained_root.elements[j], proof.root.elements[j]);
     }
     measure_gates_end!(builder, measure);
 }
@@ -139,7 +130,6 @@ impl MerkleClaimAndProofTarget {
     pub fn new_virtual(max_depth: usize, builder: &mut CircuitBuilder<F, D>) -> Self {
         MerkleClaimAndProofTarget {
             max_depth,
-            enabled: builder.add_virtual_bool_target_safe(),
             root: builder.add_virtual_hash(),
             key: builder.add_virtual_value(),
             value: builder.add_virtual_value(),
@@ -154,12 +144,7 @@ impl MerkleClaimAndProofTarget {
     }
     /// assigns the given values to the targets
     #[allow(clippy::too_many_arguments)]
-    pub fn set_targets(
+    pub fn set_targets(&self, pw: &mut PartialWitness<F>, mp: &MerkleClaimAndProof) -> Result<()> {
-        &self,
-        pw: &mut PartialWitness<F>,
-        enabled: bool,
-        mp: &MerkleClaimAndProof,
-    ) -> Result<()> {
         if mp.proof.siblings.len() > self.max_depth {
             return Err(Error::Tree(TreeError::circuit_depth_too_small(
                 self.max_depth,
@@ -167,7 +152,6 @@ impl MerkleClaimAndProofTarget {
             )));
         }
 
-        pw.set_bool_target(self.enabled, enabled)?;
         pw.set_hash_target(self.root, HashOut::from_vec(mp.root.0.to_vec()))?;
         pw.set_target_arr(&self.key.elements, &mp.key.0)?;
         pw.set_target_arr(&self.value.elements, &mp.value.0)?;
@@ -207,8 +191,6 @@ impl MerkleClaimAndProofTarget {
 #[derive(Clone, Serialize, Deserialize)]
 pub struct MerkleProofExistenceTarget {
     max_depth: usize,
-    // `enabled` determines if the merkleproof verification is enabled
-    pub(crate) enabled: BoolTarget,
     pub(crate) root: HashOutTarget,
     pub(crate) key: ValueTarget,
     pub(crate) value: ValueTarget,
@@ -236,16 +218,9 @@ pub fn verify_merkle_proof_existence_circuit(
     let obtained_root =
         compute_root_from_leaf(max_depth, builder, &path, &leaf_hash, &proof.siblings);
 
-    // check that obtained_root==root (from inputs), when enabled==true
+    // check that obtained_root==root (from inputs)
-    let zero = builder.zero();
-    let expected_root: Vec<Target> = (0..HASH_SIZE)
-        .map(|j| builder.select(proof.enabled, proof.root.elements[j], zero))
-        .collect();
-    let computed_root: Vec<Target> = (0..HASH_SIZE)
-        .map(|j| builder.select(proof.enabled, obtained_root.elements[j], zero))
-        .collect();
     for j in 0..HASH_SIZE {
-        builder.connect(computed_root[j], expected_root[j]);
+        builder.connect(obtained_root.elements[j], proof.root.elements[j]);
     }
     measure_gates_end!(builder, measure);
 
@@ -256,7 +231,6 @@ impl MerkleProofExistenceTarget {
     pub fn new_virtual(max_depth: usize, builder: &mut CircuitBuilder<F, D>) -> Self {
         MerkleProofExistenceTarget {
             max_depth,
-            enabled: builder.add_virtual_bool_target_safe(),
             root: builder.add_virtual_hash(),
             key: builder.add_virtual_value(),
             value: builder.add_virtual_value(),
@@ -265,12 +239,7 @@ impl MerkleProofExistenceTarget {
         }
     }
     /// assigns the given values to the targets
-    pub fn set_targets(
+    pub fn set_targets(&self, pw: &mut PartialWitness<F>, mp: &MerkleClaimAndProof) -> Result<()> {
-        &self,
-        pw: &mut PartialWitness<F>,
-        enabled: bool,
-        mp: &MerkleClaimAndProof,
-    ) -> Result<()> {
         assert!(mp.proof.existence); // sanity check
         if mp.proof.siblings.len() > self.max_depth {
             return Err(Error::Tree(TreeError::circuit_depth_too_small(
@@ -279,7 +248,6 @@ impl MerkleProofExistenceTarget {
             )));
         }
 
-        pw.set_bool_target(self.enabled, enabled)?;
         pw.set_hash_target(self.root, HashOut::from_vec(mp.root.0.to_vec()))?;
         pw.set_target_arr(&self.key.elements, &mp.key.0)?;
         pw.set_target_arr(&self.value.elements, &mp.value.0)?;
@@ -456,8 +424,6 @@ fn hash_with_flag_target<H: AlgebraicHasher<F>>(
 #[derive(Clone, Serialize, Deserialize)]
 pub struct MerkleTreeStateTransitionProofTarget {
     pub(crate) max_depth: usize,
-    // `enabled` determines if the merkleproof state transition verification is enabled
-    pub(crate) enabled: BoolTarget,
     pub(crate) op: Target,
     pub(crate) old_root: HashOutTarget,
     pub(crate) op_proof: MerkleClaimAndProofTarget,
@@ -511,7 +477,6 @@ pub fn verify_merkle_state_transition_circuit(
     };
     let new_key_proof = MerkleProofExistenceTarget {
         max_depth: proof.max_depth,
-        enabled: proof.enabled,
         root,
         key: proof.op_key,
         value: proof.op_value,
@@ -523,13 +488,7 @@ pub fn verify_merkle_state_transition_circuit(
     // Insert/Delete: Non-existence
     // Update: Existence
     let proof_type = is_update;
-    builder.conditional_assert_eq(
+    builder.connect(proof.op_proof.existence.target, proof_type.target);
-        proof.enabled.target,
-        proof.op_proof.existence.target,
-        proof_type.target,
-    );
-    // 3.2) assert that proof.enabled matches with op_proof.enabled
-    builder.connect(proof.op_proof.enabled.target, proof.enabled.target);
 
     // 4) assert proof_non_existence.root corresponds to the root
     // specified by the op (old_root for Insert/Update and new_root
@@ -545,17 +504,9 @@ pub fn verify_merkle_state_transition_circuit(
     };
     for j in 0..HASH_SIZE {
         // 4.1) assert that proof.proof_non_existence.root == proof.old_root
-        builder.conditional_assert_eq(
+        builder.connect(proof.op_proof.root.elements[j], claim_root.elements[j]);
-            proof.enabled.target,
-            proof.op_proof.root.elements[j],
-            claim_root.elements[j],
-        );
         // 4.2) assert that the non-existence proof uses the op_key (value not needed).
-        builder.conditional_assert_eq(
+        builder.connect(proof.op_proof.key.elements[j], proof.op_key.elements[j]);
-            proof.enabled.target,
-            proof.op_proof.key.elements[j],
-            proof.op_key.elements[j],
-        );
     }
 
     // prepare value for check 5.2)
@@ -593,7 +544,7 @@ pub fn verify_merkle_state_transition_circuit(
             .map(|j| builder.select(is_divergence_level, zero, new_siblings[i].elements[j]))
             .collect();
         for j in 0..HASH_SIZE {
-            builder.conditional_assert_eq(proof.enabled.target, old_sibling_i[j], new_sibling_i[j]);
+            builder.connect(old_sibling_i[j], new_sibling_i[j]);
         }
 
         // 5.2) when i==d && if old_siblings[i] != new_siblings[i], check that:
@@ -611,7 +562,7 @@ pub fn verify_merkle_state_transition_circuit(
         let in_case_5_2 = builder.and(old_is_noteq_new, is_divergence_level);
 
         // do the case2's checks
-        let sel = builder.and(proof.enabled, in_case_5_2);
+        let sel = in_case_5_2;
         for j in 0..HASH_SIZE {
             builder.conditional_assert_eq(sel.target, old_siblings[i].elements[j], zero);
             builder.conditional_assert_eq(
@@ -641,7 +592,6 @@ impl MerkleTreeStateTransitionProofTarget {
     pub fn new_virtual(max_depth: usize, builder: &mut CircuitBuilder<F, D>) -> Self {
         Self {
             max_depth,
-            enabled: builder.add_virtual_bool_target_safe(),
             op: builder.add_virtual_target(),
 
             old_root: builder.add_virtual_hash(),
@@ -661,7 +611,6 @@ impl MerkleTreeStateTransitionProofTarget {
     pub fn set_targets(
         &self,
         pw: &mut PartialWitness<F>,
-        enabled: bool,
         mp: &MerkleTreeStateTransitionProof,
     ) -> Result<()> {
         let new_siblings = mp.siblings.clone();
@@ -672,13 +621,11 @@ impl MerkleTreeStateTransitionProofTarget {
             )));
         }
 
-        pw.set_bool_target(self.enabled, enabled)?;
         pw.set_target(self.op, F::from_canonical_u8(mp.op as u8))?;
 
         pw.set_hash_target(self.old_root, HashOut::from_vec(mp.old_root.0.to_vec()))?;
         self.op_proof.set_targets(
             pw,
-            enabled,
             &MerkleClaimAndProof {
                 root: if mp.op == MerkleTreeOp::Delete {
                     mp.new_root
@@ -859,7 +806,6 @@ pub mod tests {
         verify_merkle_proof_circuit(&mut builder, &targets);
         targets.set_targets(
             &mut pw,
-            true,
             &MerkleClaimAndProof::new(tree.root(), key, Some(value), proof),
         )?;
 
@@ -871,6 +817,42 @@ pub mod tests {
         Ok(())
     }
 
+    #[test]
+    fn test_merkleproof_pad_valid() -> Result<()> {
+        // circuit
+        let config = CircuitConfig::standard_recursion_config();
+        let mut builder = CircuitBuilder::<F, D>::new(config);
+        let mut pw = PartialWitness::<F>::new();
+
+        let targets = MerkleClaimAndProofTarget::new_virtual(32, &mut builder);
+        verify_merkle_proof_circuit(&mut builder, &targets);
+        targets.set_targets(&mut pw, &MerkleClaimAndProof::pad())?;
+
+        // generate & verify proof
+        let data = builder.build::<C>();
+        let proof = data.prove(pw)?;
+        data.verify(proof)?;
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_merkleproof_transition_pad_valid() -> Result<()> {
+        let config = CircuitConfig::standard_recursion_config();
+        let mut builder = CircuitBuilder::<F, D>::new(config);
+        let mut pw = PartialWitness::<F>::new();
+
+        let targets = MerkleTreeStateTransitionProofTarget::new_virtual(32, &mut builder);
+        verify_merkle_state_transition_circuit(&mut builder, &targets);
+        targets.set_targets(&mut pw, &MerkleTreeStateTransitionProof::pad())?;
+
+        // generate & verify proof
+        let data = builder.build::<C>();
+        let proof = data.prove(pw)?;
+        data.verify(proof)?;
+        Ok(())
+    }
+
     #[test]
     fn test_merkleproof_only_existence_verify() -> Result<()> {
         for max_depth in [10, 16, 32, 40, 64, 128, 130, 250, 256] {
@@ -906,7 +888,6 @@ pub mod tests {
         verify_merkle_proof_circuit(&mut builder, &targets);
         targets.set_targets(
             &mut pw,
-            true,
             &MerkleClaimAndProof::new(tree.root(), key, Some(value), proof),
         )?;
 
@@ -982,7 +963,6 @@ pub mod tests {
         verify_merkle_proof_circuit(&mut builder, &targets);
         targets.set_targets(
             &mut pw,
-            true,
             &MerkleClaimAndProof::new(tree.root(), key, Some(value), proof),
         )?;
 
@@ -1028,32 +1008,15 @@ pub mod tests {
 
         let targets = MerkleClaimAndProofTarget::new_virtual(max_depth, &mut builder);
         verify_merkle_proof_circuit(&mut builder, &targets);
-        // verification enabled & proof of existence
+        // proof of existence
         let mp = MerkleClaimAndProof::new(tree2.root(), key, Some(value), proof);
-        targets.set_targets(&mut pw, true, &mp)?;
+        targets.set_targets(&mut pw, &mp)?;
 
         // generate proof, expecting it to fail (since we're using the wrong
         // root)
         let data = builder.build::<C>();
         assert!(data.prove(pw).is_err());
 
-        // Now generate a new proof, using `enabled=false`, which should pass the verification
-        // despite containing 'wrong' witness.
-        let config = CircuitConfig::standard_recursion_config();
-        let mut builder = CircuitBuilder::<F, D>::new(config);
-        let mut pw = PartialWitness::<F>::new();
-
-        let targets = MerkleClaimAndProofTarget::new_virtual(max_depth, &mut builder);
-        verify_merkle_proof_circuit(&mut builder, &targets);
-        // verification disabled & proof of existence
-        targets.set_targets(&mut pw, false, &mp)?;
-
-        // generate proof, should pass despite using wrong witness, since the
-        // `enabled=false`
-        let data = builder.build::<C>();
-        let proof = data.prove(pw)?;
-        data.verify(proof)?;
-
         Ok(())
     }
 
@@ -1076,7 +1039,7 @@ pub mod tests {
 
         let targets = MerkleTreeStateTransitionProofTarget::new_virtual(max_depth, &mut builder);
         verify_merkle_state_transition_circuit(&mut builder, &targets);
-        targets.set_targets(&mut pw, true, state_transition_proof)?;
+        targets.set_targets(&mut pw, state_transition_proof)?;
 
         // generate & verify proof
         let data = builder.build::<C>();
@@ -1273,71 +1236,4 @@ pub mod tests {
         assert_ne!(state_transition_proof.new_root, tree.root()); // Tamper check
         Ok(())
     }
-
-    #[test]
-    fn test_state_transition_gadget_disabled() -> Result<()> {
-        let max_depth: usize = 32;
-        let mut kvs = HashMap::new();
-        for i in 0..8 {
-            kvs.insert(RawValue::from(i), RawValue::from(1000 + i));
-        }
-        let mut tree = MerkleTree::new(&kvs);
-
-        let key = RawValue::from(37);
-        let value = RawValue::from(1037);
-        let _ = tree.insert(&key, &value)?;
-
-        let key = RawValue::from(21);
-        let value = RawValue::from(1021);
-        let original_state_transition_proof = tree.insert(&key, &value)?;
-
-        let mut state_transition_proof = original_state_transition_proof.clone();
-
-        // modify the proof, so that it should fail when `enabled=true`, by
-        // changing the new_root
-        state_transition_proof.new_root = state_transition_proof.old_root;
-
-        run_circuit_disabled(max_depth, &state_transition_proof)?;
-
-        // modify the proof, so that it should fail when `enabled=true`, by
-        // changing the new_sibling at the divergence level, which should not
-        // pass the verification in the case where we're inserting key=21
-        let mut state_transition_proof = original_state_transition_proof.clone();
-        state_transition_proof.siblings[4] = EMPTY_HASH;
-
-        run_circuit_disabled(max_depth, &state_transition_proof)?;
-
-        Ok(())
-    }
-
-    fn run_circuit_disabled(
-        max_depth: usize,
-        state_transition_proof: &MerkleTreeStateTransitionProof,
-    ) -> Result<()> {
-        let config = CircuitConfig::standard_recursion_config();
-        let mut builder = CircuitBuilder::<F, D>::new(config);
-        let mut pw = PartialWitness::<F>::new();
-
-        let targets = MerkleTreeStateTransitionProofTarget::new_virtual(max_depth, &mut builder);
-        verify_merkle_state_transition_circuit(&mut builder, &targets);
-        targets.set_targets(&mut pw, true, state_transition_proof)?;
-
-        // generate proof, and expect it to fail
-        let data = builder.build::<C>();
-        assert!(data.prove(pw).is_err()); // expect prove to fail
-
-        let config = CircuitConfig::standard_recursion_config();
-        let mut builder = CircuitBuilder::<F, D>::new(config);
-        let mut pw = PartialWitness::<F>::new();
-
-        let targets = MerkleTreeStateTransitionProofTarget::new_virtual(max_depth, &mut builder);
-        verify_merkle_state_transition_circuit(&mut builder, &targets);
-        targets.set_targets(&mut pw, false, state_transition_proof)?;
-
-        // generate and expect it to pass
-        let data = builder.build::<C>();
-        let proof = data.prove(pw)?;
-        data.verify(proof)?;
-        Ok(())
-    }
 }

src/backends/plonky2/primitives/merkletree/mod.rs

@@ -921,6 +921,21 @@ impl MerkleClaimAndProof {
             },
         }
     }
+    /// Value used for padding.  This is a valid merkle proof.
+    pub fn pad() -> Self {
+        let [key, value] = [EMPTY_VALUE, EMPTY_VALUE];
+        let root = kv_hash(&key, Some(value));
+        Self {
+            root,
+            key,
+            value,
+            proof: MerkleProof {
+                existence: true,
+                siblings: vec![],
+                other_leaf: None,
+            },
+        }
+    }
     pub fn new(root: Hash, key: RawValue, value: Option<RawValue>, proof: MerkleProof) -> Self {
         Self {
             root,
@@ -974,7 +989,6 @@ pub struct MerkleTreeStateTransitionProof {
 }
 
 impl MerkleTreeStateTransitionProof {
-    /// Value used for padding.
     pub fn empty() -> Self {
         let empty_proof_and_claim = MerkleClaimAndProof::empty();
         Self {
@@ -988,6 +1002,20 @@ impl MerkleTreeStateTransitionProof {
             siblings: vec![],
         }
     }
+    /// Value used for padding.  This is a valid transition proof.
+    pub fn pad() -> Self {
+        let pad_proof_and_claim = MerkleClaimAndProof::pad();
+        Self {
+            op: MerkleTreeOp::Update,
+            old_root: pad_proof_and_claim.root,
+            op_proof: pad_proof_and_claim.proof,
+            new_root: pad_proof_and_claim.root,
+            op_key: pad_proof_and_claim.key,
+            op_value: pad_proof_and_claim.value,
+            value: Some(pad_proof_and_claim.value),
+            siblings: vec![],
+        }
+    }
 }
 
 // NOTE: currently we use automatic serialization/deserialization, which is
@@ -1165,6 +1193,15 @@ pub mod tests {
         Ok(())
     }
 
+    #[test]
+    fn test_merkletree_pad() {
+        let claim = MerkleClaimAndProof::pad();
+        MerkleTree::verify(claim.root, &claim.proof, &claim.key, &claim.value).unwrap();
+
+        let proof = MerkleTreeStateTransitionProof::pad();
+        MerkleTree::verify_state_transition(&proof).unwrap();
+    }
+
     #[test]
     fn test_key_not_found() -> Result<()> {
         let db = Box::new(db::MemDB::new());

src/frontend/multi_pod/diagnostics.rs

@@ -78,12 +78,12 @@ fn aggregate_rows<'a>(
         UtilizationRow {
             name: "merkle proofs",
             used: merkle_proofs,
-            limit: params.max_merkle_proofs_containers,
+            limit: params.containers.state.max_medium,
         },
         UtilizationRow {
             name: "merkle state transitions",
             used: merkle_state_transitions,
-            limit: params.max_merkle_tree_state_transition_proofs_containers,
+            limit: params.containers.transition.max_medium,
         },
         UtilizationRow {
             name: "custom pred verifications",
@@ -278,15 +278,24 @@ mod tests {
     use super::*;
     use crate::{
         frontend::multi_pod::cost::CustomPredicateId,
-        middleware::{Hash, RawValue},
+        middleware::{Hash, ParamsContainers, ParamsMerkleProofs, RawValue},
     };
 
     fn default_params() -> Params {
         Params {
             max_statements: 48,
             max_public_statements: 8,
-            max_merkle_proofs_containers: 8,
+            containers: ParamsContainers {
-            max_merkle_tree_state_transition_proofs_containers: 4,
+                state: ParamsMerkleProofs {
+                    max_small: 0,
+                    max_medium: 8,
+                },
+                transition: ParamsMerkleProofs {
+                    max_small: 0,
+                    max_medium: 4,
+                },
+                ..Default::default()
+            },
             max_custom_predicate_verifications: 10,
             max_custom_predicates: 2,
             max_signed_by: 4,

src/frontend/multi_pod/solver.rs

@@ -395,13 +395,11 @@ pub fn solve(input: &SolverInput) -> Result<MultiPodSolution> {
         let lb_statement_groups = lower_bound_from_total(input.num_statements, max_stmts_per_pod);
         let lb_merkle = lower_bound_from_total(
             resource_totals.merkle_proofs,
-            input.params.max_merkle_proofs_containers,
+            input.params.containers.state.max_medium,
         );
         let lb_merkle_transitions = lower_bound_from_total(
             resource_totals.merkle_state_transitions,
-            input
+            input.params.containers.transition.max_medium,
-                .params
-                .max_merkle_tree_state_transition_proofs_containers,
         );
         let lb_custom_pred_verifications = lower_bound_from_total(
             resource_totals.custom_pred_verifications,
@@ -753,7 +751,7 @@ fn try_solve_with_pods(
             .map(|s| (input.costs[s].merkle_proofs as f64) * prove[s][p])
             .sum();
         model.add_constraint(constraint!(
-            merkle_sum <= (input.params.max_merkle_proofs_containers as f64) * pod_used[p]
+            merkle_sum <= (input.params.containers.state.max_medium as f64) * pod_used[p]
         ));
 
         // 6d: Merkle state transitions
@@ -761,11 +759,7 @@ fn try_solve_with_pods(
             .map(|s| (input.costs[s].merkle_state_transitions as f64) * prove[s][p])
             .sum();
         model.add_constraint(constraint!(
-            mst_sum
+            mst_sum <= (input.params.containers.transition.max_medium as f64) * pod_used[p]
-                <= (input
-                    .params
-                    .max_merkle_tree_state_transition_proofs_containers as f64)
-                    * pod_used[p]
         ));
 
         // 6e: Custom predicate verifications

src/middleware/mod.rs

@@ -780,6 +780,50 @@ pub const BASE_PARAMS: BaseParams = BaseParams {
     max_operation_args: 5 + 1,
 };
 
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, JsonSchema, Hash)]
+#[serde(rename_all = "camelCase")]
+pub struct ParamsMerkleProofs {
+    pub max_small: usize,
+    pub max_medium: usize,
+}
+
+impl ParamsMerkleProofs {
+    pub fn max_total(&self) -> usize {
+        self.max_small + self.max_medium
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, JsonSchema, Hash)]
+#[serde(rename_all = "camelCase")]
+pub struct ParamsContainers {
+    // Parameters for exists/nonexists container operations.  The small set only supports exists
+    pub state: ParamsMerkleProofs,
+    // Parameters for transition container operations (insert, delete, update).  The small set only
+    // supports update.
+    pub transition: ParamsMerkleProofs,
+    // Max depth of small proofs
+    pub max_depth_small: usize,
+    // Max depth of medium proofs
+    pub max_depth_medium: usize,
+}
+
+impl Default for ParamsContainers {
+    fn default() -> Self {
+        Self {
+            state: ParamsMerkleProofs {
+                max_small: 22,
+                max_medium: 8,
+            },
+            transition: ParamsMerkleProofs {
+                max_small: 12,
+                max_medium: 6,
+            },
+            max_depth_small: 8,
+            max_depth_medium: 32,
+        }
+    }
+}
+
 /// Params: non dynamic parameters that define the circuit.
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, JsonSchema, Hash)]
 #[serde(rename_all = "camelCase")]
@@ -793,12 +837,7 @@ pub struct Params {
     // max number of operations using custom predicates that can be verified in the MainPod
     pub max_custom_predicate_verifications: usize,
     pub max_custom_predicate_wildcards: usize,
-    // maximum number of merkle proofs used for container operations
+    pub containers: ParamsContainers,
-    pub max_merkle_proofs_containers: usize,
-    // maximum number of merkle tree state transition proofs used for container update operations
-    pub max_merkle_tree_state_transition_proofs_containers: usize,
-    // maximum depth for merkle tree gadget used for container operations
-    pub max_depth_mt_containers: usize,
     // maximum depth of the merkle tree gadget used for verifier_data membership
     // check.  This allows creating verifying sets of pod circuits of size
     // 2^max_depth_mt_vds.  Limits the number of container operations of the type Contains,
@@ -820,9 +859,7 @@ impl Default for Params {
             max_custom_predicates: 8,
             max_custom_predicate_verifications: 8,
             max_custom_predicate_wildcards: 8,
-            max_merkle_proofs_containers: 20,
+            containers: ParamsContainers::default(),
-            max_merkle_tree_state_transition_proofs_containers: 6,
-            max_depth_mt_containers: 32,
             max_depth_mt_vds: 6, // up to 64 (2^6) different pod circuits
             max_public_key_of: 2,
             max_signed_by: 4,