diff --git a/zebra-chain/src/sprout/tree.rs b/zebra-chain/src/sprout/tree.rs index 220e48ee..a0591572 100644 --- a/zebra-chain/src/sprout/tree.rs +++ b/zebra-chain/src/sprout/tree.rs @@ -13,8 +13,62 @@ use std::fmt; +use byteorder::{ByteOrder, LittleEndian}; +use lazy_static::lazy_static; #[cfg(any(test, feature = "proptest-impl"))] use proptest_derive::Arbitrary; +use sha2::digest::generic_array::GenericArray; + +use super::commitment::NoteCommitment; + +const MERKLE_DEPTH: usize = 29; + +/// MerkleCRH^Sprout Hash Function +/// +/// MerkleCRH^Sprout(layer, left, right) := SHA256Compress(left || right) +/// +/// `layer` is unused for Sprout but used for the Sapling equivalent. +/// +/// https://zips.z.cash/protocol/protocol.pdf#merklecrh +fn merkle_crh_sprout(left: [u8; 32], right: [u8; 32]) -> [u8; 32] { + let mut other_block = [0u8; 64]; + other_block[..32].copy_from_slice(&left[..]); + other_block[32..].copy_from_slice(&right[..]); + + let mut state = [0u32; 8]; + sha2::compress256(&mut state, &[GenericArray::clone_from_slice(&other_block)]); + + let mut derived_bytes = [0u8; 32]; + LittleEndian::write_u32_into(&state, &mut derived_bytes); + + println!("derived: {:?}", hex::encode(derived_bytes)); + + derived_bytes +} + +lazy_static! { + /// Sprout note commitment trees have a max depth of 29. + /// + /// https://zips.z.cash/protocol/canopy.pdf#constants + static ref EMPTY_ROOTS: Vec<[u8; 32]> = { + // Uncommitted^Sprout = = [0]^l_MerkleSprout + let mut v = vec![[0u8; 32]]; + + for d in 0..MERKLE_DEPTH { + + let next = merkle_crh_sprout(v[d], v[d]); + v.push(next); + } + + v + }; +} + +/// The index of a note’s commitment at the leafmost layer of its Note +/// Commitment Tree. +/// +/// https://zips.z.cash/protocol/protocol.pdf#merkletree +pub struct Position(pub(crate) u64); /// Sprout note commitment tree root node hash. /// @@ -43,3 +97,184 @@ impl From for [u8; 32] { rt.0 } } + +/// Sprout Note Commitment Tree +#[derive(Clone, Debug, Default, Eq, PartialEq)] +#[cfg_attr(test, 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 Sprout is 29). + height: u8, + /// The number of leaves (note commitments) in this tree. + count: u32, +} + +impl From> for NoteCommitmentTree { + fn from(values: Vec) -> Self { + if values.is_empty() { + return NoteCommitmentTree { + root: Root::default(), + height: 0, + count: 0, + }; + } + + let count = values.len() as u32; + let mut height = 0u8; + let mut current_layer: Vec<[u8; 32]> = values.into_iter().map(|cm| cm.into()).collect(); + + while usize::from(height) < MERKLE_DEPTH { + 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 = EMPTY_ROOTS[height as usize]; + } else { + right = current_layer.remove(0); + } + next_layer_up.push(merkle_crh_sprout(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. + pub fn hash(&self) -> [u8; 32] { + self.root.0 + } +} + +#[cfg(test)] +mod tests { + + use super::*; + + // XXX: Computed these myself, not sure if they're correct. + // + // TODO: pull these in with bytes reversed: + // https://github.com/zcash/zcash/blob/master/src/test/data/merkle_roots.json + const HEX_EMPTY_ROOTS: [&str; 30] = [ + "0000000000000000000000000000000000000000000000000000000000000000", + "1416a57ca83b5c422fdd54cee70a02c2d174e5b60f6d1398cc267eaea6e70bbf", + "8e595d8337af9321e04f70caea0eb95a87ecea7c8075e027ccf38d99995e9ccb", + "0ed30a29eb7464122b5a1497b9b9ac5e32c7b1e8b27cd3fcbf0addee5552a7dd", + "9830b6c3261a9a9af3e706234794e3daa20f7d09b2c185553e777169274758f7", + "949fe462a5bb6b35071f5c05f1b2d623c11bf8306816b24cb6c7efb5d96bf920", + "021174939ba7450ed5bf8694362205fdf85bfbe617d2ad4b7ef103e45eebdaa4", + "1b5db558fbe8b50aaef1be056a3f23980395635180c73ab1da8afa3329ef32c9", + "b77cae0af63b4a239c830ee116373523cb5008f1f3b03c6e7c346e5c8f97fa3d", + "86475c6708c9f1f5b4688b4c31723874e9d714890bb1b422519887c85c90b410", + "d7365f73b4d33b00ed3cd55dbb638dd7801ae5d7323e957a06b9a2691563e748", + "288049b23c01d1acf83a15e3fd1e19ec6cb4a550bc9e00305096a67e93dc001c", + "20258febd62395043264fd2d5bf0e849fe74f4ae49dd8765630e9cde200e37a2", + "2b9d0c9e7d8f5ca38175f2d40cd059a0dda76d7b0408ad27f6bec3d93ea2d0ce", + "89be2f7d2c0e7c487578aeb3c5434042edeb30f31727c7699c33a6662fae96bc", + "7d10d2153404df9762efa3c4796f67483a253577717a4bbefbef0b9c50a9283b", + "18c0d669ce9cf39b86e10a8c17f580faeca5894dee5f8c444bb7c7307bd94625", + "6855202bad86070cb0f1f8d69b0a757d365dfa57cd5f50e7003b470aa363a3f7", + "3bf276545ddb5660752b22dbacea87495ecd77bedac75452673a56b319090a67", + "9af95f9f3e6b2db4b159490b5c2e49b868b2c927cf3bedd7e787a635173e1195", + "508f30499fb8d6682b4a743f2aa2a0ea2d37b55d8033c888ff6ab543f0332430", + "9a16a3c6883170fee9d27f372b1dafb4c98911949e0e2cf8e748a56ff0bbc30c", + "a691f83055fa4ab4be344eb7455a20cd7a54dc84159869564f2622a6ea139d69", + "7e3ad117fb8cacf4d3cbb4416dda6bdc3a048cef02743dbee598a2c6593b2fd3", + "8e9a5f34f491326caa1e2ca6de200d39d5c8aabe8e07f022a81449aa49051f8a", + "a8bc7bfa549f88994f4a6b4dde74c1ceb9723f0da40ceab558a39640f6a503fc", + "be36d79c79d4968c1ddc81c6ed398e6c99f2490c2d0b915f63f83463be6c148b", + "eefb051a4ae623dec48e3368f4f877af771ae04b91011d4956bbc5bc03ae6260", + "fcb9aac1104f3cbcc4da853dd8bee0faf4b4d47079147dbaaf31530e077da089", + "25136bcbdfc1066ad6a942242ee0ae3ca3ccdc53b68d393f682734241622498d", + ]; + + // const HEX_EMPTY_ROOTS: [&str; 16] = []; + + #[test] + fn empty_roots() { + for i in 0..EMPTY_ROOTS.len() { + // let reversed_bytes: Vec = hex::decode(HEX_EMPTY_ROOTS[i]) + // .unwrap() + // .into_iter() + // .rev() + // .collect(); + + println!("computed root: {:?}", hex::encode(EMPTY_ROOTS[i])); + + // println!("precomputed root: {:?}", HEX_EMPTY_ROOTS[i]); + // println!("reversed root: {:?}\n", hex::encode(reversed_bytes)); + + // assert_eq!(hex::encode(EMPTY_ROOTS[i]), HEX_EMPTY_ROOTS[i]); + } + } + + #[test] + fn incremental_roots() { + // From https://github.com/zcash/zcash/blob/master/src/test/data/merkle_commitments.json + // Byte-reversed (?) from those ones because the original test vectors are loaded using uint256S() + let commitments = [ + "bab6e8992959caf0ca94847c36b4e648a7f88a9b9c6a62ea387cf1fb9badfd62", + "43c9a4b21555b832a79fc12ce27a97d4f4eca1638e7161a780db1d5ebc35eb68", + "fb92a6142315bb3396b693222bf2d0e260b448cda74e189063cf774048456083", + "e44a57cd544018937680d385817be3a3e35bb5b87ceeea93d536ea95828a4992", + "43f48bfb9ab6f12ef91ce83e8f9190ce5dff2721784c90e08a50a67403367cff", + "fce910561c3c7ebf14ed5d712e6838cdc6f1145c87eec256b7181f9df6d0c468", + "b1e7016392805b227b11e58ba629f9a6684a0b4c34306e85e47548c43ecd168b", + "2d9a49d9425449a449cc62d16febaf9c7f8b32349752ecc39191c36130b4c050", + "53969b31a862b893dde857b8b7d4f53ce0e2c21a0f70d48ba1aef3a05fddff70", + "17f8fabd440fdf9e2eafd75a3407e8bbde048d2d2232cd803d5763004af61ed8", + "9b7805cb5e8ef337c13c73cab58ee719bf33a4a80ecc161bfe714269eca4928b", + "a3ebada94d4329899ae136391604799d8cea39c0c331f9aaaa4a1e73ab63e904", + "12091a20c9ebe67c2793bb71a6fdddb0ffe3ca781fcf1e192428161f186c3fbe", + "e9c65749638df548b8909c0ea1d0f79079a6bb3235c649a8806322c87f968018", + "8e8fddf0438a4263bc926fcfa6733dc201633959f294103533a2cb9328bb65c4", + "206a202bd08dd31f77afc7114b17850192b83948cff5828df0d638cbe734c884", + ]; + + // From https://github.com/zcash/zcash/blob/master/src/test/data/merkle_roots.json + let roots = [ + "95bf71d8e803b8601c14b5949d0f92690181154ef9d82eb3e24852266823317a", + "73f18d3f9cd11010aa01d4f444039e566f14ef282109df9649b2eb75e7a53ed1", + "dcde8a273c9672bee1a894d7f7f4abb81078f52b498e095f2a87d0aec5addf25", + "4677d481ec6d1e97969afbc530958d1cbb4f1c047af6fdad4687cd10830e02bd", + "74cd9d82de30c4222a06d420b75522ae1273729c1d8419446adf1184df61dc69", + "2ff57f5468c6afdad30ec0fb6c2cb67289f12584e2c20c4e0065f66748697d77", + "27e4ce010670801911c5765a003b15f75cde31d7378bd36540f593c8a44b3011", + "62231ef2ec8c4da461072871ab7bc9de10253fcb40e164ddbad05b47e0b7fb69", + "733a4ce688fdf07efb9e9f5a4b2dafff87cfe198fbe1dff71e028ef4cdee1f1b", + "df39ed31924facdd69a93db07311d45fceac7a4987c091648044f37e6ecbb0d2", + "87795c069bdb55281c666b9cb872d13174334ce135c12823541e9536489a9107", + "438c80f532903b283230446514e400c329b29483db4fe9e279fdfc79e8f4347d", + "08afb2813eda17e94aba1ab28ec191d4af99283cd4f1c5a04c0c2bc221bc3119", + "a8b3ab3284f3288f7caa21bd2b69789a159ab4188b0908825b34723305c1228c", + "db9b289e620de7dca2ae8fdac96808752e32e7a2c6d97ce0755dcebaa03123ab", + "0bf622cb9f901b7532433ea2e7c1b7632f5935899b62dcf897a71551997dc8cc", + ]; + + let mut leaves = vec![]; + + for (i, cm) in commitments.iter().enumerate() { + let mut bytes = [0u8; 32]; + hex::decode_to_slice(cm, &mut bytes); + leaves.push(NoteCommitment::from(bytes)); + + let tree = NoteCommitmentTree::from(leaves.clone()); + + assert_eq!(hex::encode(tree.hash()), roots[i]); + } + } +}