branching for non-existing proof

privacy-scaling-explorations · Apr 2, 2024 · 91325b9 · 91325b9
1 parent 9817e1d
commit 91325b9
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Showing 6 changed files with 45 additions and 22 deletions.
diff --git a/geth-utils/gethutil/mpt/witness/branch.go b/geth-utils/gethutil/mpt/witness/branch.go
@@ -115,7 +115,7 @@ func prepareBranchNode(branch1, branch2, extNode1, extNode2, extListRlpBytes []b
 	extensionBranch := ExtensionBranchNode{
 		IsExtension:   isExtension,
 		IsPlaceholder: [2]bool{isBranchSPlaceholder, isBranchCPlaceholder},
-		IsLastLevel:   isLastLevel,
+		IsLastLevelAndWrongExtCase:   isLastLevel,
 		Extension:     extensionNode,
 		Branch:        branchNode,
 	}
@@ -283,7 +283,7 @@ func addBranchAndPlaceholder(proof1, proof2 [][]byte,
 		driftedInd := getDriftedPosition(leafRow0, numberOfNibbles)
 
 		node = prepareBranchNode(proof1[len1-2], proof1[len1-2], extNode, extNode, extListRlpBytes, extValues,
-			key[keyIndex+numberOfNibbles], driftedInd, false, true, isExtension, true)
+			key[keyIndex+numberOfNibbles], driftedInd, false, true, isExtension, false)
 
 		// We now get the first nibble of the leaf that was turned into branch.
 		// This first nibble presents the position of the leaf once it moved
@@ -295,7 +295,7 @@ func addBranchAndPlaceholder(proof1, proof2 [][]byte,
 		driftedInd := getDriftedPosition(leafRow0, numberOfNibbles)
 
 		node = prepareBranchNode(proof2[len2-2], proof2[len2-2], extNode, extNode, extListRlpBytes, extValues,
-			key[keyIndex+numberOfNibbles], driftedInd, true, false, isExtension, true)
+			key[keyIndex+numberOfNibbles], driftedInd, true, false, isExtension, false)
 	}
 
 	return isModifiedExtNode, isExtension, numberOfNibbles, node

diff --git a/geth-utils/gethutil/mpt/witness/nodes.go b/geth-utils/gethutil/mpt/witness/nodes.go
@@ -70,7 +70,7 @@ type ExtensionBranchNode struct {
 	// nibbles of the original extension node).
 	IsModExtension [2]bool       `json:"is_mod_extension"`
 	IsPlaceholder  [2]bool       `json:"is_placeholder"`
-	IsLastLevel    bool          `json:"is_last_level"`
+	IsLastLevelAndWrongExtCase    bool          `json:"is_last_level_and_wrong_ext_case"`
 	Extension      ExtensionNode `json:"extension"`
 	Branch         BranchNode    `json:"branch"`
 }

diff --git a/zkevm-circuits/src/mpt_circuit/account_leaf.rs b/zkevm-circuits/src/mpt_circuit/account_leaf.rs
@@ -6,7 +6,7 @@ use halo2_proofs::{
 };
 
 use super::{
-    helpers::{ext_key_rlc_calc_value, KeyDataWitness, ListKeyGadget, MainData, ParentDataWitness},
+    helpers::{KeyDataWitness, ListKeyGadget, MainData, ParentDataWitness},
     mod_extension::ModExtensionGadget,
     rlp_gadgets::RLPItemWitness,
     witness_row::{AccountRowType, Node},
@@ -22,7 +22,7 @@ use crate::{
     evm_circuit::util::from_bytes,
     mpt_circuit::{
         helpers::{
-            ext_key_rlc_expr, key_memory, main_memory, num_nibbles, parent_memory, DriftedGadget, Indexable, IsPlaceholderLeafGadget, KeyData, MPTConstraintBuilder, ParentData, WrongExtNodeGadget, WrongLeafGadget, KECCAK
+            key_memory, main_memory, num_nibbles, parent_memory, DriftedGadget, Indexable, IsPlaceholderLeafGadget, KeyData, MPTConstraintBuilder, ParentData, WrongExtNodeGadget, WrongLeafGadget, KECCAK
         },
         param::{EMPTY_TRIE_HASH, KEY_LEN_IN_NIBBLES, RLP_LIST_LONG, RLP_LONG},
         MPTConfig, MPTContext, MptMemory, RlpItemType,
@@ -392,6 +392,21 @@ impl<F: Field> AccountLeafConfig<F> {
             let wrong_ext_after_nibbles =
                 ctx.rlp_item(meta, cb, AccountRowType::ShortExtNodeNibbles as usize, RlpItemType::Nibbles);
 
+            // The extension_branch in the last level needs has `is_last_level_and_wrong_ext_case = true`
+            // in the case of wrong extension node.
+            // All other extension_branches (above it) need to have it `false` (constraint in
+            // extension_branch.rs)
+            // TODO: Use is_last_level_and_wrong_ext_case as a flag for one of the three cases
+            // require!(config.parent_data[1].is_last_level_and_wrong_ext_case.expr() => true.expr());
+            // TODO: use C proof everywhere for non-existing proof.
+
+            // TODO: when non-existing-proof, it needs to be one of the following cases:
+            // wrong leaf, wrong extension node, nil leaf - we need to check the sum of these
+            // three cases is 1.
+            // To check whether it's the wrong leaf case - parent is not extension, leaf is not placeholder
+            // To check whether it's wrong extension node - is_last_level_and_wrong_ext_case = 1, parent is extension
+            // To check whether it's the nil leaf - use IsPlaceholderLeafGadget
+
             config.wrong_ext_node = WrongExtNodeGadget::construct(
                 cb,
                 key_item.hash_rlc(),

diff --git a/zkevm-circuits/src/mpt_circuit/extension_branch.rs b/zkevm-circuits/src/mpt_circuit/extension_branch.rs
@@ -26,7 +26,7 @@ pub(crate) struct ExtensionBranchConfig<F> {
     parent_data: [ParentData<F>; 2],
     is_placeholder: [Cell<F>; 2],
     is_extension: Cell<F>,
-    is_last_level: Cell<F>,
+    is_last_level_and_wrong_ext_case: Cell<F>,
     extension: ExtensionGadget<F>,
     branch: BranchGadget<F>,
 }
@@ -42,7 +42,7 @@ impl<F: Field> ExtensionBranchConfig<F> {
         circuit!([meta, cb], {
             // General inputs
             config.is_extension = cb.query_bool();
-            config.is_last_level = cb.query_bool();
+            config.is_last_level_and_wrong_ext_case = cb.query_bool();
             // If we're in a placeholder, both the extension and the branch parts are
             // placeholders
             for is_s in [true, false] {
@@ -140,6 +140,11 @@ impl<F: Field> ExtensionBranchConfig<F> {
 
             // Set the new keys
             for is_s in [true, false] {
+                // The extension_branch in the last level needs to have `is_ext_last_level = true` (checked
+                // in account_leaf.rs / storage_leaf.rs).
+                // All other extension_branches need to have it `false`:
+                require!(config.parent_data[is_s.idx()].is_last_level_and_wrong_ext_case.expr() => false.expr());
+
                 ifx! {not!(config.is_placeholder[is_s.idx()].expr()) => {
                     KeyData::store(
                         cb,
@@ -161,7 +166,7 @@ impl<F: Field> ExtensionBranchConfig<F> {
                         false.expr(),
                         false.expr(),
                         config.is_extension.expr(),
-                        config.is_last_level.expr(),
+                        config.is_last_level_and_wrong_ext_case.expr(),
                         WordLoHi::zero(),
                     );
                  } elsex {
@@ -189,9 +194,9 @@ impl<F: Field> ExtensionBranchConfig<F> {
                         config.parent_data[is_s.idx()].is_root.expr(),
                         true.expr(),
                         config.is_extension.expr(),
-                        config.is_last_level.expr(),
+                        config.is_last_level_and_wrong_ext_case.expr(),
                         branch.mod_word[is_s.idx()].clone(),
-                    );
+                    ); 
                 }}
             }
         });
@@ -214,8 +219,8 @@ impl<F: Field> ExtensionBranchConfig<F> {
         let is_extension = extension_branch.is_extension.scalar();
         self.is_extension.assign(region, offset, is_extension)?;
 
-        let is_last_level = extension_branch.is_last_level.scalar();
-        self.is_last_level.assign(region, offset, is_last_level)?;
+        let is_last_level_and_wrong_ext_case = extension_branch.is_last_level_and_wrong_ext_case.scalar();
+        self.is_last_level_and_wrong_ext_case.assign(region, offset, is_last_level_and_wrong_ext_case)?;
 
         let key_data =
             self.key_data
@@ -301,7 +306,7 @@ impl<F: Field> ExtensionBranchConfig<F> {
                     false,
                     false,
                     is_extension == 1.into(),
-                    is_last_level == 1.into(),
+                    is_last_level_and_wrong_ext_case == 1.into(),
                     WordLoHi::zero(),
                 )?;
             } else {
@@ -325,7 +330,7 @@ impl<F: Field> ExtensionBranchConfig<F> {
                     parent_data[is_s.idx()].is_root,
                     true,
                     is_extension == 1.into(),
-                    is_last_level == 1.into(),
+                    is_last_level_and_wrong_ext_case == 1.into(),
                     mod_node_hash_word[is_s.idx()],
                 )?;
             }

diff --git a/zkevm-circuits/src/mpt_circuit/helpers.rs b/zkevm-circuits/src/mpt_circuit/helpers.rs
@@ -561,10 +561,11 @@ pub(crate) struct ParentData<F> {
     // is_extension is used only in a non-existing proof / wrong extension node case -
     // in account/storage leaf to check whether the parent is an extension node
     pub(crate) is_extension: Cell<F>,
-    // is_ext_last_level is used only in a non-existing proof - in wrong extension node case the branch
-    // is a placeholder and the check for a branch hash being in the parent extension node needs to be ignored,
-    // but it needs to be ignored only in the last branch (the branch above the leaf into which the lookup is made)
-    pub(crate) is_ext_last_level: Cell<F>,
+    // is_last_level_and_wrong_ext_case is used only in a non-existing proof in wrong extension node case -
+    // the last branch is a placeholder in this case and the check for a branch hash being in the parent
+    // extension node needs to be ignored, but it needs to be ignored only in the last branch
+    // (the branch above the leaf into which the lookup is made)
+    pub(crate) is_last_level_and_wrong_ext_case: Cell<F>,
     pub(crate) drifted_parent_hash: WordLoHiCell<F>,
 }
 
@@ -591,7 +592,7 @@ impl<F: Field> ParentData<F> {
             is_root: cb.query_cell(),
             is_placeholder: cb.query_cell(),
             is_extension: cb.query_cell(),
-            is_ext_last_level: cb.query_cell(),
+            is_last_level_and_wrong_ext_case: cb.query_cell(),
             drifted_parent_hash: cb.query_word_unchecked(),
         };
         circuit!([meta, cb.base], {
@@ -605,7 +606,7 @@ impl<F: Field> ParentData<F> {
                     parent_data.is_root.expr(),
                     parent_data.is_placeholder.expr(),
                     parent_data.is_extension.expr(),
-                    parent_data.is_ext_last_level.expr(),
+                    parent_data.is_last_level_and_wrong_ext_case.expr(),
                     parent_data.drifted_parent_hash.lo().expr(),
                     parent_data.drifted_parent_hash.hi().expr(),
                 ],
@@ -686,7 +687,7 @@ impl<F: Field> ParentData<F> {
         self.is_root.assign(region, offset, values[3])?;
         self.is_placeholder.assign(region, offset, values[4])?;
         self.is_extension.assign(region, offset, values[5])?;
-        self.is_ext_last_level.assign(region, offset, values[6])?;
+        self.is_last_level_and_wrong_ext_case.assign(region, offset, values[6])?;
         self.drifted_parent_hash
             .lo()
             .assign(region, offset, values[7])?;

diff --git a/zkevm-circuits/src/mpt_circuit/witness_row.rs b/zkevm-circuits/src/mpt_circuit/witness_row.rs
@@ -138,6 +138,8 @@ pub struct ExtensionBranchNode {
     /// TODO Doc.
     pub is_extension: bool,
     /// TODO Doc.
+    pub is_last_level_and_wrong_ext_case: bool,
+    /// TODO Doc.
     pub(crate) is_mod_extension: [bool; 2],
     /// TODO Doc.
     pub is_placeholder: [bool; 2],