feat!: replace MerkleMembershipConstraint with`ComputeMerkleRootCon…

…straint` (#385)

* feat: replace `MerkleMembershipConstraint` with`ComputeMerkleRootConstraint`

* Update acir_format.cpp

cpp/src/barretenberg/dsl/acir_format/acir_format.cpp

@@ -50,9 +50,9 @@ void create_circuit(Composer& composer, const acir_format& constraint_system)
         create_sha256_constraints(composer, constraint);
     }
 
-    // Add merkle membership constraints
-    for (const auto& constraint : constraint_system.merkle_membership_constraints) {
-        create_merkle_check_membership_constraint(composer, constraint);
+    // Add compute merkle root constraints
+    for (const auto& constraint : constraint_system.compute_merkle_root_constraints) {
+        create_compute_merkle_root_constraint(composer, constraint);
     }
 
     // Add schnorr constraints
@@ -128,9 +128,9 @@ Composer create_circuit(const acir_format& constraint_system,
         create_sha256_constraints(composer, constraint);
     }
 
-    // Add merkle membership constraints
-    for (const auto& constraint : constraint_system.merkle_membership_constraints) {
-        create_merkle_check_membership_constraint(composer, constraint);
+    // Add compute merkle root constraints
+    for (const auto& constraint : constraint_system.compute_merkle_root_constraints) {
+        create_compute_merkle_root_constraint(composer, constraint);
     }
 
     // Add schnorr constraints
@@ -212,9 +212,9 @@ Composer create_circuit_with_witness(const acir_format& constraint_system,
         create_sha256_constraints(composer, constraint);
     }
 
-    // Add merkle membership constraints
-    for (const auto& constraint : constraint_system.merkle_membership_constraints) {
-        create_merkle_check_membership_constraint(composer, constraint);
+    // Add compute merkle root constraints
+    for (const auto& constraint : constraint_system.compute_merkle_root_constraints) {
+        create_compute_merkle_root_constraint(composer, constraint);
     }
 
     // Add schnorr constraints
@@ -293,9 +293,9 @@ Composer create_circuit_with_witness(const acir_format& constraint_system, std::
         create_sha256_constraints(composer, constraint);
     }
 
-    // Add merkle membership constraints
-    for (const auto& constraint : constraint_system.merkle_membership_constraints) {
-        create_merkle_check_membership_constraint(composer, constraint);
+    // Add compute merkle root constraints
+    for (const auto& constraint : constraint_system.compute_merkle_root_constraints) {
+        create_compute_merkle_root_constraint(composer, constraint);
     }
 
     // Add schnorr constraints
@@ -372,9 +372,9 @@ void create_circuit_with_witness(Composer& composer, const acir_format& constrai
         create_sha256_constraints(composer, constraint);
     }
 
-    // Add merkle membership constraints
-    for (const auto& constraint : constraint_system.merkle_membership_constraints) {
-        create_merkle_check_membership_constraint(composer, constraint);
+    // Add compute merkle root constraints
+    for (const auto& constraint : constraint_system.compute_merkle_root_constraints) {
+        create_compute_merkle_root_constraint(composer, constraint);
     }
 
     // Add schnorr constraints

cpp/src/barretenberg/dsl/acir_format/acir_format.hpp

@@ -6,7 +6,7 @@
 #include "fixed_base_scalar_mul.hpp"
 #include "schnorr_verify.hpp"
 #include "ecdsa_secp256k1.hpp"
-#include "merkle_membership_constraint.hpp"
+#include "compute_merkle_root_constraint.hpp"
 #include "pedersen.hpp"
 #include "hash_to_field.hpp"
 #include "barretenberg/dsl/types.hpp"
@@ -28,7 +28,7 @@ struct acir_format {
     std::vector<Blake2sConstraint> blake2s_constraints;
     std::vector<HashToFieldConstraint> hash_to_field_constraints;
     std::vector<PedersenConstraint> pedersen_constraints;
-    std::vector<MerkleMembershipConstraint> merkle_membership_constraints;
+    std::vector<ComputeMerkleRootConstraint> compute_merkle_root_constraints;
     // A standard plonk arithmetic constraint, as defined in the poly_triple struct, consists of selector values
     // for q_M,q_L,q_R,q_O,q_C and indices of three variables taking the role of left, right and output wire
     std::vector<poly_triple> constraints;
@@ -60,7 +60,7 @@ template <typename B> inline void read(B& buf, acir_format& data)
     read(buf, data.logic_constraints);
     read(buf, data.range_constraints);
     read(buf, data.sha256_constraints);
-    read(buf, data.merkle_membership_constraints);
+    read(buf, data.compute_merkle_root_constraints);
     read(buf, data.schnorr_constraints);
     read(buf, data.ecdsa_constraints);
     read(buf, data.blake2s_constraints);
@@ -78,7 +78,7 @@ template <typename B> inline void write(B& buf, acir_format const& data)
     write(buf, data.logic_constraints);
     write(buf, data.range_constraints);
     write(buf, data.sha256_constraints);
-    write(buf, data.merkle_membership_constraints);
+    write(buf, data.compute_merkle_root_constraints);
     write(buf, data.schnorr_constraints);
     write(buf, data.ecdsa_constraints);
     write(buf, data.blake2s_constraints);

cpp/src/barretenberg/dsl/acir_format/acir_format.test.cpp

@@ -88,7 +88,7 @@ TEST(acir_format, test_logic_gate_from_noir_circuit)
         .blake2s_constraints = {},
         .hash_to_field_constraints = {},
         .pedersen_constraints = {},
-        .merkle_membership_constraints = {},
+        .compute_merkle_root_constraints = {},
         .constraints = { expr_a, expr_b, expr_c, expr_d },
     };
 
@@ -152,7 +152,7 @@ TEST(acir_format, test_schnorr_verify_pass)
         .blake2s_constraints = {},
         .hash_to_field_constraints = {},
         .pedersen_constraints = {},
-        .merkle_membership_constraints = {},
+        .compute_merkle_root_constraints = {},
         .constraints = { poly_triple{
             .a = schnorr_constraint.result,
             .b = schnorr_constraint.result,
@@ -221,7 +221,7 @@ TEST(acir_format, test_schnorr_verify_small_range)
         .blake2s_constraints = {},
         .hash_to_field_constraints = {},
         .pedersen_constraints = {},
-        .merkle_membership_constraints = {},
+        .compute_merkle_root_constraints = {},
         .constraints = { poly_triple{
             .a = schnorr_constraint.result,
             .b = schnorr_constraint.result,
@@ -249,4 +249,4 @@ TEST(acir_format, test_schnorr_verify_small_range)
     auto verifier = composer.create_ultra_with_keccak_verifier();
 
     EXPECT_EQ(verifier.verify_proof(proof), true);
-}
+}

cpp/src/barretenberg/dsl/acir_format/merkle_membership_constraint.cpp → cpp/src/barretenberg/dsl/acir_format/compute_merkle_root_constraint.cpp

@@ -1,21 +1,18 @@
-#include "merkle_membership_constraint.hpp"
+#include "compute_merkle_root_constraint.hpp"
 #include "barretenberg/stdlib/merkle_tree/membership.hpp"
 
 namespace acir_format {
 
-void create_merkle_check_membership_constraint(Composer& composer, const MerkleMembershipConstraint& input)
+void create_compute_merkle_root_constraint(Composer& composer, const ComputeMerkleRootConstraint& constraint)
 {
     // Convert value from a witness index into a field element.
     // This is the hash of the message. In Barretenberg, this would be input.value = hash_value(message)
-    field_ct leaf = field_ct::from_witness_index(&composer, input.leaf);
+    field_ct leaf = field_ct::from_witness_index(&composer, constraint.leaf);
 
     // Convert index from a witness index into a byte array
-    field_ct index_field = field_ct::from_witness_index(&composer, input.index);
+    field_ct index_field = field_ct::from_witness_index(&composer, constraint.index);
     auto index_bits = index_field.decompose_into_bits();
 
-    // Convert root into a field_ct
-    field_ct root = field_ct::from_witness_index(&composer, input.root);
-
     // We are given the HashPath as a Vec<fr>
     // We want to first convert it into a Vec<(fr, fr)> then cast this to hash_path
     // struct which requires the method create_witness_hashpath
@@ -24,20 +21,21 @@ void create_merkle_check_membership_constraint(Composer& composer, const MerkleM
     // In Noir we accept a hash path that only contains one hash per tree level
     // It is ok to reuse the leaf as it will be overridden in check_subtree_membership when computing the current root
     // at each tree level
-    for (size_t i = 0; i < input.hash_path.size(); i++) {
+    for (size_t i = 0; i < constraint.hash_path.size(); i++) {
         if (!index_bits[i].get_value()) {
             field_ct left = leaf;
-            field_ct right = field_ct::from_witness_index(&composer, input.hash_path[i]);
+            field_ct right = field_ct::from_witness_index(&composer, constraint.hash_path[i]);
             hash_path.push_back(std::make_pair(left, right));
         } else {
-            field_ct left = field_ct::from_witness_index(&composer, input.hash_path[i]);
+            field_ct left = field_ct::from_witness_index(&composer, constraint.hash_path[i]);
             field_ct right = leaf;
             hash_path.push_back(std::make_pair(left, right));
         }
     }
 
-    auto exists = plonk::stdlib::merkle_tree::check_subtree_membership(root, hash_path, leaf, index_bits, 0);
-    composer.assert_equal_constant(exists.witness_index, fr::one());
+    auto merkle_root = plonk::stdlib::merkle_tree::compute_subtree_root(hash_path, leaf, index_bits, 0);
+
+    composer.assert_equal(merkle_root.witness_index, constraint.result);
 }
 
 } // namespace acir_format

cpp/src/barretenberg/dsl/acir_format/merkle_membership_constraint.hpp → cpp/src/barretenberg/dsl/acir_format/compute_merkle_root_constraint.hpp

@@ -4,33 +4,30 @@
 
 namespace acir_format {
 
-struct MerkleMembershipConstraint {
+struct ComputeMerkleRootConstraint {
     std::vector<uint32_t> hash_path; // Vector of pairs of hashpaths. eg indices 0,1 denotes the pair (0,1)
-    uint32_t root;                   // Single field element -- field_t
     uint32_t leaf;                   // Single field element -- field_t
-    uint32_t result;                 // Single field element -- bool_t
+    uint32_t result;                 // Single field element -- field_t
     uint32_t index;
 
-    friend bool operator==(MerkleMembershipConstraint const& lhs, MerkleMembershipConstraint const& rhs) = default;
+    friend bool operator==(ComputeMerkleRootConstraint const& lhs, ComputeMerkleRootConstraint const& rhs) = default;
 };
 
-void create_merkle_check_membership_constraint(Composer& composer, const MerkleMembershipConstraint& input);
+void create_compute_merkle_root_constraint(Composer& composer, const ComputeMerkleRootConstraint& input);
 
-template <typename B> inline void read(B& buf, MerkleMembershipConstraint& constraint)
+template <typename B> inline void read(B& buf, ComputeMerkleRootConstraint& constraint)
 {
     using serialize::read;
     read(buf, constraint.hash_path);
-    read(buf, constraint.root);
     read(buf, constraint.leaf);
     read(buf, constraint.result);
     read(buf, constraint.index);
 }
 
-template <typename B> inline void write(B& buf, MerkleMembershipConstraint const& constraint)
+template <typename B> inline void write(B& buf, ComputeMerkleRootConstraint const& constraint)
 {
     using serialize::write;
     write(buf, constraint.hash_path);
-    write(buf, constraint.root);
     write(buf, constraint.leaf);
     write(buf, constraint.result);
     write(buf, constraint.index);

cpp/src/barretenberg/stdlib/merkle_tree/membership.hpp

@@ -10,9 +10,8 @@ namespace merkle_tree {
 
 template <typename ComposerContext> using bit_vector = std::vector<bool_t<ComposerContext>>;
 /**
- * Checks if the subtree is correctly inserted at a specified index in a Merkle tree.
+ * Computes the new merkle root if the subtree is correctly inserted at a specified index in a Merkle tree.
  *
- * @param root: The root of the latest state of the merkle tree,
  * @param hashes: The hash path from any leaf in the subtree to the root, it doesn't matter if this hash path is
  * computed before or after updating the tree,
  * @param value: The value of the subtree root,
@@ -24,12 +23,11 @@ template <typename ComposerContext> using bit_vector = std::vector<bool_t<Compos
  * @see Check full documentation: https://hackmd.io/2zyJc6QhRuugyH8D78Tbqg?view
  */
 template <typename Composer>
-bool_t<Composer> check_subtree_membership(field_t<Composer> const& root,
-                                          hash_path<Composer> const& hashes,
-                                          field_t<Composer> const& value,
-                                          bit_vector<Composer> const& index,
-                                          size_t at_height,
-                                          bool const is_updating_tree = false)
+field_t<Composer> compute_subtree_root(hash_path<Composer> const& hashes,
+                                       field_t<Composer> const& value,
+                                       bit_vector<Composer> const& index,
+                                       size_t at_height,
+                                       bool const is_updating_tree = false)
 {
     auto current = value;
     for (size_t i = at_height; i < hashes.size(); ++i) {
@@ -46,7 +44,32 @@ bool_t<Composer> check_subtree_membership(field_t<Composer> const& root,
         current = pedersen_hash<Composer>::hash_multiple({ left, right }, 0, is_updating_tree);
     }
 
-    return (current == root);
+    return current;
+}
+
+/**
+ * Checks if the subtree is correctly inserted at a specified index in a Merkle tree.
+ *
+ * @param root: The root of the latest state of the merkle tree,
+ * @param hashes: The hash path from any leaf in the subtree to the root, it doesn't matter if this hash path is
+ * computed before or after updating the tree,
+ * @param value: The value of the subtree root,
+ * @param index: The index of any leaf in the subtree,
+ * @param at_height: The height of the subtree,
+ * @param is_updating_tree: set to true if we're updating the tree.
+ * @tparam Composer: type of composer.
+ *
+ * @see Check full documentation: https://hackmd.io/2zyJc6QhRuugyH8D78Tbqg?view
+ */
+template <typename Composer>
+bool_t<Composer> check_subtree_membership(field_t<Composer> const& root,
+                                          hash_path<Composer> const& hashes,
+                                          field_t<Composer> const& value,
+                                          bit_vector<Composer> const& index,
+                                          size_t at_height,
+                                          bool const is_updating_tree = false)
+{
+    return (compute_subtree_root(hashes, value, index, at_height, is_updating_tree) == root);
 }
 
 /**