Review submittd PR

.gitignore

@@ -6,3 +6,6 @@
 
 # Ignore Goland and JetBrains IDE files
 .idea/
+
+# Visual Studio Code
+.vscode

docs/mapstore.md

@@ -1,21 +1,17 @@
-# MapStore
-
-<!-- toc -->
+# MapStore <!-- omit in toc -->
 
+- [Introduction](#introduction)
 - [Implementations](#implementations)
   - [SimpleMap](#simplemap)
   - [BadgerV4](#badgerv4)
+- [Note On External Writability](#note-on-external-writability)
 
-<!-- tocstop -->
+## Introduction
 
 The `MapStore` is a simple interface used by the SM(S)T to store, delete and
 retrieve key-value pairs. It is intentionally simple and minimalistic so as to
 enable different key-value engines to implement and back the trie database.
 
-Any key-value store used by the tries should **not** be able to be externally
-writeable in production. This opens the possibility to attacks where the writer
-can modify the trie database and prove values that were not inserted.
-
 See: [the interface](../kvstore/interfaces.go) for a more detailed description
 of the simple interface required by the SM(S)T.
 
@@ -35,11 +31,15 @@ See [simplemap.go](../kvstore/simplemap/simplemap.go) for more details.
 
 ### BadgerV4
 
-This library provides a wrapper around [dgraph-io/badger][badgerv4] to adhere to
+This library provides a wrapper around [dgraph-io/badger][https://github.com/dgraph-io/badger] to adhere to
 the `MapStore` interface. See the [full documentation](./badger-store.md) for
 additional functionality and implementation details.
 
 See: [badger](../kvstore/badger/) for more details on the implementation of this
 submodule.
 
-[badgerv4]: https://github.com/dgraph-io/badger
+## Note On External Writability
+
+Any key-value store used by the tries should **not** be able to be externally
+writeable in production. This opens the possibility to attacks where the writer
+can modify the trie database and prove values that were not inserted.

docs/smt.md

@@ -1,6 +1,4 @@
-# smt
-
-<!-- toc -->
+# smt <!-- omit in toc -->
 
 - [Overview](#overview)
 - [Implementation](#implementation)
@@ -16,7 +14,8 @@
   - [Visualisation](#visualisation)
 - [Values](#values)
   - [Nil values](#nil-values)
-- [Hashers & Digests](#hashers--digests)
+- [Hashers \& Digests](#hashers--digests)
+  - [Hash Function Recommendations](#hash-function-recommendations)
 - [Roots](#roots)
 - [Proofs](#proofs)
   - [Verification](#verification)
@@ -31,8 +30,6 @@
   - [Data Loss](#data-loss)
 - [Sparse Merkle Sum Trie](#sparse-merkle-sum-trie)
 
-<!-- tocstop -->
-
 ## Overview
 
 Sparse Merkle Tries (SMTs) are efficient and secure data structures for storing
@@ -44,25 +41,6 @@ make SMTs valuable in applications like blockchains, decentralized databases,
 and authenticated data structures, providing optimized and trustworthy data
 storage and verification.
 
-Although any hash function that satisfies the `hash.Hash` interface can be used
-to construct the trie it is **strongly recommended** to use a hashing function
-that provides the following properties:
-
-- **Collision resistance**: The hash function must be collision resistant, in
-  order for the inputs of the SMT to be unique.
-- **Preimage resistance**: The hash function must be preimage resistant, to
-  protect against the attack of the Merkle tree construction attacks where the
-  attacker can modify unknown data.
-- **Efficiency**: The hash function must be efficient, as it is used to compute
-  the hash of many nodes in the trie.
-
-Therefore it is recommended to use a hashing function such as:
-
-- `sha256`
-- `sha3_256`/`keccak256`
-
-Or another sufficiently secure hashing algorithm.
-
 See [smt.go](../smt.go) for more details on the implementation.
 
 ## Implementation
@@ -362,6 +340,20 @@ graph TD
 	VH --ValueHash-->L
 ```
 
+### Hash Function Recommendations
+
+Although any hash function that satisfies the `hash.Hash` interface can be used
+to construct the trie, it is **strongly recommended** to use a hashing function
+that provides the following properties:
+
+- **Collision resistance**: The hash function must be collision resistant. This
+  is needed in order for the inputs of the SMT to be unique.
+- **Preimage resistance**: The hash function must be preimage resistant. This
+  is needed to protect against the Merkle tree construction attacks where
+  the attacker can modify unknown data.
+- **Efficiency**: The hash function must be efficient, as it is used to compute
+  the hash of many nodes in the trie.
+
 ## Roots
 
 The root of the tree is a slice of bytes. `MerkleRoot` is an alias for `[]byte`.

proofs.go

@@ -341,9 +341,9 @@ func VerifyClosestProof(proof *SparseMerkleClosestProof, root []byte, spec *Trie
 	if err := proof.validateBasic(spec); err != nil {
 		return false, errors.Join(ErrBadProof, err)
 	}
-	// Create a new TrieSpec with a nil path hasher - as the ClosestProof
-	// already contains a hashed path, double hashing it will invalidate the
-	// proof.
+	// Create a new TrieSpec with a nil path hasher.
+	// Since the ClosestProof already contains a hashed path, double hashing it
+	// will invalidate the proof.
 	nilSpec := &TrieSpec{
 		th:      spec.th,
 		ph:      newNilPathHasher(spec.ph.PathSize()),

smt.go

@@ -177,7 +177,6 @@ func (smt *SMT) update(
 			return newLeaf, nil
 		}
 		// We insert an "extension" representing multiple single-branch inner nodes
-		last := &node
 		var newInner *innerNode
 		if getPathBit(path, prefixlen) == left {
 			newInner = &innerNode{
@@ -191,6 +190,7 @@ func (smt *SMT) update(
 			}
 		}
 		// Determine if we need to insert an extension or a branch
+		last := &node
 		if depth < prefixlen {
 			// note: this keeps path slice alive - GC inefficiency?
 			if depth > 0xff {