feat: add zero element to the tree

csv/entry_13.csv

@@ -0,0 +1,14 @@
+username,balance_ETH_ETH,balance_USDT_ETH
+dxGaEAii,11888,41163
+MBlfbBGI,67823,18651
+lAhWlEWZ,18651,2087
+nuZweYtO,22073,55683
+gbdSwiuY,34897,83296
+RZNneNuP,83296,16881
+YsscHXkp,31699,35479
+RkLzkDun,2087,79731
+HlQlnEYI,30605,11888
+RqkZOFYe,16881,14874
+NjCSRAfD,41163,67823
+pHniJMQY,14874,22073
+dOGIMzKR,10032,10032

csv/entry_17.csv

@@ -0,0 +1,19 @@
+username,balance_ETH_ETH,balance_USDT_ETH
+dxGaEAii,11888,41163
+MBlfbBGI,67823,18651
+lAhWlEWZ,18651,2087
+nuZweYtO,22073,55683
+gbdSwiuY,34897,83296
+RZNneNuP,83296,16881
+YsscHXkp,31699,35479
+RkLzkDun,2087,79731
+HlQlnEYI,30605,11888
+RqkZOFYe,16881,14874
+NjCSRAfD,41163,67823
+pHniJMQY,14874,22073
+dOGIMzKR,10032,10032
+HfMDmNLp,55683,34897
+xPLKzCBl,79731,30605
+AtwIxZHo,35479,31699
+HuIIxzHo,1,1
+

zk_prover/src/merkle_sum_tree/mst.rs

@@ -65,28 +65,6 @@ pub struct Cryptocurrency {
 }
 
 impl<const N_CURRENCIES: usize, const N_BYTES: usize> MerkleSumTree<N_CURRENCIES, N_BYTES> {
-    pub fn from_params(
-        root: Node<N_CURRENCIES>,
-        nodes: Vec<Vec<Node<N_CURRENCIES>>>,
-        depth: usize,
-        entries: Vec<Entry<N_CURRENCIES>>,
-        cryptocurrencies: Vec<Cryptocurrency>,
-        is_sorted: bool,
-    ) -> Result<Self, Box<dyn std::error::Error>>
-    where
-        [usize; N_CURRENCIES + 1]: Sized,
-        [usize; N_CURRENCIES + 2]: Sized,
-    {
-        Ok(MerkleSumTree::<N_CURRENCIES, N_BYTES> {
-            root,
-            nodes,
-            depth,
-            entries,
-            cryptocurrencies,
-            is_sorted,
-        })
-    }
-
     /// Builds a Merkle Sum Tree from a CSV file stored at `path`. The CSV file must be formatted as follows:
     ///
     /// `username,balance_<cryptocurrency>_<chain>,balance_<cryptocurrency>_<chain>,...`
@@ -120,8 +98,9 @@ impl<const N_CURRENCIES: usize, const N_BYTES: usize> MerkleSumTree<N_CURRENCIES
         Self::from_entries(entries, cryptocurrencies, true)
     }
 
+    /// Builds a Merkle Sum Tree from a vector of entries
     pub fn from_entries(
-        entries: Vec<Entry<N_CURRENCIES>>,
+        mut entries: Vec<Entry<N_CURRENCIES>>,
         cryptocurrencies: Vec<Cryptocurrency>,
         is_sorted: bool,
     ) -> Result<MerkleSumTree<N_CURRENCIES, N_BYTES>, Box<dyn std::error::Error>>
@@ -133,6 +112,14 @@ impl<const N_CURRENCIES: usize, const N_BYTES: usize> MerkleSumTree<N_CURRENCIES
 
         let mut nodes = vec![];
 
+        // Pad the entries with empty entries to make the number of entries equal to 2^depth
+        if entries.len() < 2usize.pow(depth as u32) {
+            entries.extend(vec![
+                Entry::init_empty();
+                2usize.pow(depth as u32) - entries.len()
+            ]);
+        }
+
         let leaves = build_leaves_from_entries(&entries);
 
         let root = build_merkle_tree_from_leaves(&leaves, depth, &mut nodes)?;
@@ -147,6 +134,29 @@ impl<const N_CURRENCIES: usize, const N_BYTES: usize> MerkleSumTree<N_CURRENCIES
         })
     }
 
+    /// Builds a Merkle Sum Tree from a root node, a vector of nodes, a depth, a vector of entries, a vector of cryptocurrencies and a boolean indicating whether the leaves are sorted by the username byte values.
+    pub fn from_params(
+        root: Node<N_CURRENCIES>,
+        nodes: Vec<Vec<Node<N_CURRENCIES>>>,
+        depth: usize,
+        entries: Vec<Entry<N_CURRENCIES>>,
+        cryptocurrencies: Vec<Cryptocurrency>,
+        is_sorted: bool,
+    ) -> Result<Self, Box<dyn std::error::Error>>
+    where
+        [usize; N_CURRENCIES + 1]: Sized,
+        [usize; N_CURRENCIES + 2]: Sized,
+    {
+        Ok(MerkleSumTree::<N_CURRENCIES, N_BYTES> {
+            root,
+            nodes,
+            depth,
+            entries,
+            cryptocurrencies,
+            is_sorted,
+        })
+    }
+
     /// Updates the balances of the entry with the given username and returns the new root of the tree.
     ///
     /// # Arguments

zk_prover/src/merkle_sum_tree/tests.rs

@@ -41,7 +41,7 @@ mod test {
         assert_eq!(root.balances, merkle_tree_2.root().balances);
 
         // should create valid proof for each entry in the tree and verify it
-        for i in 0..15 {
+        for i in 0..=15 {
             let proof = merkle_tree.generate_proof(i).unwrap();
             assert!(merkle_tree.verify_proof(&proof));
         }
@@ -198,4 +198,56 @@ mod test {
         // The hash of the leaf should match the hash computed from the hash preimage
         assert_eq!(leaf.hash, computed_leaf.hash);
     }
+
+    #[test]
+    fn test_tree_with_zero_element_1() {
+        // create new merkle tree
+        let merkle_tree =
+            MerkleSumTree::<N_CURRENCIES, N_BYTES>::from_csv("../csv/entry_13.csv").unwrap();
+
+        // get root
+        let root = merkle_tree.root();
+
+        // expect root hash to be different than 0
+        assert!(root.hash != 0.into());
+        // expect balance to match the sum of all entries
+        assert!(root.balances == [385969.into(), 459661.into()]);
+        // expect depth to be 4
+        assert!(*merkle_tree.depth() == 4_usize);
+
+        // should create valid proof for each entry in the tree and verify it
+        for i in 0..=15 {
+            let proof = merkle_tree.generate_proof(i).unwrap();
+            assert!(merkle_tree.verify_proof(&proof));
+        }
+
+        // shouldn't create a proof for an entry that doesn't exist in the tree
+        assert!(merkle_tree.generate_proof(16).is_err());
+    }
+
+    #[test]
+    fn test_tree_with_zero_element_2() {
+        // create new merkle tree
+        let merkle_tree =
+            MerkleSumTree::<N_CURRENCIES, N_BYTES>::from_csv("../csv/entry_17.csv").unwrap();
+
+        // get root
+        let root = merkle_tree.root();
+
+        // expect root hash to be different than 0
+        assert!(root.hash != 0.into());
+        // expect balance to match the sum of all entries
+        assert!(root.balances == [556863.into(), 556863.into()]);
+        // expect depth to be 5
+        assert!(*merkle_tree.depth() == 5_usize);
+
+        // should create valid proof for each entry in the tree and verify it
+        for i in 0..=31 {
+            let proof = merkle_tree.generate_proof(i).unwrap();
+            assert!(merkle_tree.verify_proof(&proof));
+        }
+
+        // shouldn't create a proof for an entry that doesn't exist in the tree
+        assert!(merkle_tree.generate_proof(32).is_err());
+    }
 }