Incomplete impl of Sapling note commitment merkle tree

zebra-chain/src/sapling/tree.rs

@@ -13,15 +13,13 @@
 #![allow(clippy::unit_arg)]
 #![allow(dead_code)]
 
-use std::{fmt, io};
+use std::fmt;
 
 use bitvec::prelude::*;
 #[cfg(any(test, feature = "proptest-impl"))]
 use proptest_derive::Arbitrary;
 
-use crate::serialization::{SerializationError, ZcashDeserialize, ZcashSerialize};
-
-use super::commitment::pedersen_hashes::pedersen_hash;
+use super::commitment::{pedersen_hashes::pedersen_hash, NoteCommitment};
 
 /// MerkleCRH^Sapling Hash Function
 ///
@@ -46,14 +44,6 @@ fn merkle_crh_sapling(layer: u8, left: [u8; 32], right: [u8; 32]) -> [u8; 32] {
 /// https://zips.z.cash/protocol/protocol.pdf#merkletree
 pub struct Position(pub(crate) u64);
 
-// XXX: Depending on if we implement SproutNoteCommitmentTree or
-// similar, it may be worth it to define a NoteCommitmentTree trait.
-
-/// Sapling Note Commitment Tree
-#[derive(Clone, Debug, Default, Eq, PartialEq)]
-#[cfg_attr(any(test, feature = "proptest-impl"), derive(Arbitrary))]
-struct NoteCommitmentTree;
-
 /// Sapling note commitment tree root node hash.
 ///
 /// The root hash in LEBS2OSP256(rt) encoding of the Sapling note
@@ -70,37 +60,140 @@ impl fmt::Debug for Root {
     }
 }
 
-impl From<NoteCommitmentTree> for Root {
-    fn from(_tree: NoteCommitmentTree) -> Self {
-        // TODO: The Sapling note commitment tree requires a Pedersen
-        // hash function, not SHA256.
-
-        // let mut hash_writer = Sha256dWriter::default();
-        // sapling_note_commitment_tree
-        //     .zcash_serialize(&mut hash_writer)
-        //     .expect("A Sapling note commitment tree must serialize.");
-        // Self(hash_writer.finish())
+/// Sapling Note Commitment Tree
+#[derive(Clone, Debug, Default, Eq, PartialEq)]
+#[cfg_attr(any(test, feature = "proptest-impl"), derive(Arbitrary))]
+struct NoteCommitmentTree {
+    /// The root node of the tree (often used as an anchor).
+    root: Root,
+    /// The height of the tree (maximum height for Sapling is 32).
+    height: u8,
+    /// The number of leaves (note commitments) in this tree.
+    count: u32,
+}
 
+impl From<Vec<NoteCommitment>> for NoteCommitmentTree {
+    fn from(_values: Vec<NoteCommitment>) -> Self {
         unimplemented!();
     }
 }
 
+impl From<Vec<jubjub::Fq>> for NoteCommitmentTree {
+    // XXX broken
+    fn from(values: Vec<jubjub::Fq>) -> Self {
+        if values.is_empty() {
+            return NoteCommitmentTree {
+                root: Root::default(),
+                height: 0,
+                count: 0,
+            };
+        }
+
+        let count = values.len() as u32;
+        let mut height = 0;
+        let mut current_layer: Vec<[u8; 32]> =
+            values.into_iter().map(|cm_u| cm_u.to_bytes()).collect();
+
+        while current_layer.len() > 1 {
+            let mut next_layer_up = vec![];
+
+            while !current_layer.is_empty() {
+                let left = current_layer.remove(0);
+                let right;
+                if current_layer.is_empty() {
+                    right = jubjub::Fq::one().to_bytes();
+                //next_layer_up.push(current_layer.remove(0));
+                } else {
+                    //let left = current_layer.remove(0);
+                    right = current_layer.remove(0);
+                }
+                next_layer_up.push(merkle_crh_sapling(height, left, right));
+            }
+
+            height += 1;
+            current_layer = next_layer_up;
+        }
+
+        assert!(current_layer.len() == 1);
+
+        NoteCommitmentTree {
+            root: Root(current_layer.remove(0)),
+            height,
+            count,
+        }
+    }
+}
+
 impl NoteCommitmentTree {
-    /// Get the Jubjub-based Pedersen hash of root node of this merkle
-    /// tree of commitment notes.
+    /// Get the Jubjub-based Pedersen hash of root node of this merkle tree of
+    /// commitment notes.
     pub fn hash(&self) -> [u8; 32] {
-        unimplemented!();
+        self.root.0
     }
 }
 
-impl ZcashSerialize for NoteCommitmentTree {
-    fn zcash_serialize<W: io::Write>(&self, _writer: W) -> Result<(), io::Error> {
-        unimplemented!();
-    }
-}
+#[cfg(test)]
+mod tests {
 
-impl ZcashDeserialize for NoteCommitmentTree {
-    fn zcash_deserialize<R: io::Read>(_reader: R) -> Result<Self, SerializationError> {
-        unimplemented!();
+    use hex::FromHex;
+
+    use super::*;
+
+    #[test]
+    fn incremental_roots() {
+        // From https://github.com/zcash/zcash/blob/master/src/test/data/merkle_commitments_sapling.json
+        // Byte-reversed from those oens because the original test vectors are loaded using uint256S()
+        let commitments = [
+            "b02310f2e087e55bfd07ef5e242e3b87ee5d00c9ab52f61e6bd42542f93a6f55",
+            "225747f3b5d5dab4e5a424f81f85c904ff43286e0f3fd07ef0b8c6a627b11458",
+            "7c3ea01a6e3a3d90cf59cd789e467044b5cd78eb2c84cc6816f960746d0e036c",
+            "50421d6c2c94571dfaaa135a4ff15bf916681ebd62c0e43e69e3b90684d0a030",
+            "aaec63863aaa0b2e3b8009429bdddd455e59be6f40ccab887a32eb98723efc12",
+            "f76748d40d5ee5f9a608512e7954dd515f86e8f6d009141c89163de1cf351a02",
+            "bc8a5ec71647415c380203b681f7717366f3501661512225b6dc3e121efc0b2e",
+            "da1adda2ccde9381e11151686c121e7f52d19a990439161c7eb5a9f94be5a511",
+            "3a27fed5dbbc475d3880360e38638c882fd9b273b618fc433106896083f77446",
+            "c7ca8f7df8fd997931d33985d935ee2d696856cc09cc516d419ea6365f163008",
+            "f0fa37e8063b139d342246142fc48e7c0c50d0a62c97768589e06466742c3702",
+            "e6d4d7685894d01b32f7e081ab188930be6c2b9f76d6847b7f382e3dddd7c608",
+            "8cebb73be883466d18d3b0c06990520e80b936440a2c9fd184d92a1f06c4e826",
+            "22fab8bcdb88154dbf5877ad1e2d7f1b541bc8a5ec1b52266095381339c27c03",
+            "f43e3aac61e5a753062d4d0508c26ceaf5e4c0c58ba3c956e104b5d2cf67c41c",
+            "3a3661bc12b72646c94bc6c92796e81953985ee62d80a9ec3645a9a95740ac15",
+        ];
+
+        // From https://github.com/zcash/zcash/blob/master/src/test/data/merkle_roots_sapling.json
+        let _roots = [
+            "8c3daa300c9710bf24d2595536e7c80ff8d147faca726636d28e8683a0c27703",
+            "8611f17378eb55e8c3c3f0a5f002e2b0a7ca39442fc928322b8072d1079c213d",
+            "3db73b998d536be0e1c2ec124df8e0f383ae7b602968ff6a5276ca0695023c46",
+            "7ac2e6442fec5970e116dfa4f2ee606f395366cafb1fa7dfd6c3de3ce18c4363",
+            "6a8f11ab2a11c262e39ed4ea3825ae6c94739ccf94479cb69402c5722b034532",
+            "149595eed0b54a7e694cc8a68372525b9ae2c7b102514f527460db91eb690565",
+            "8c0432f1994a2381a7a4b5fda770336011f9e0b30784f9a5597901619c797045",
+            "e780c48d70420601f3313ff8488d7766b70c059c53aa3cda2ff1ef57ff62383c",
+            "f919f03caaed8a2c60f58c0d43838f83e670dc7e8ccd25daa04a13f3e8f45541",
+            "74f32b36629724038e71cbd6823b5a666440205a7d1a9242e95870b53d81f34a",
+            "a4af205a4e1ee02102866b23a68930ac33efda9235832f49b17fcc4939be4525",
+            "a946a42f1636045a16e65b2308e036d9da70089686c87c692e45912bd1cab772",
+            "a1db2dbac055364c1cb43cbeb49c7e2815bff855122602a2ad0fb981a91e0e39",
+            "16329b3ba4f0640f4d306532d9ea6ba0fbf0e70e44ed57d27b4277ed9cda6849",
+            "7b6523b2d9b23f72fec6234aa6a1f8fae3dba1c6a266023ea8b1826feba7a25c",
+            "5c0bea7e17bde5bee4eb795c2eec3d389a68da587b36dd687b134826ecc09308",
+        ];
+
+        let mut leaves = vec![];
+
+        for cm_u in commitments.iter() {
+            let bytes = <[u8; 32]>::from_hex(cm_u).unwrap();
+
+            println!("bytes: {:?}", hex::encode(bytes));
+
+            leaves.push(jubjub::Fq::from_bytes(&bytes).unwrap());
+
+            let tree = NoteCommitmentTree::from(leaves.clone());
+
+            println!("root: {:x?}", hex::encode(tree.hash()));
+        }
     }
 }