dusk-merkle

A sparsely populated Merkle Tree, parametrized over its height and arity. text Height 0 h / \ / \ / \ / \ / \ Height 1 h h / \ / \ / \ / \ Height 2 h x h h / \ / \ / \ Height 3 h x x h h h Position 0 5 6 7 The Aggregate trait defines how to calculate a parent from its children. There is no restrictions on the way the children are aggregated, it can be done with a hash function or any other custom aggregation. Empty subtrees (noted as x in the tree above) are filled with the constant EMPTY_SUBTREE from Aggregate.

Here an example where the parent is the sum of its children:

Usage

```rust use dusk_merkle::{Tree, Aggregate};

[derive(Debug, Clone, Copy, PartialEq)]

struct U8(u8);

impl From for U8 { fn from(n: u8) -> Self { Self(n) } }

const EMPTY_ITEM: U8 = U8(0);

impl Aggregate for U8 { const EMPTYSUBTREE: U8 = EMPTYITEM;

fn aggregate(items: [&Self; A]) -> Self
{
    items.into_iter().fold(U8(0), |acc, c| U8(acc.0 + c.0))
}

}

// Set the height and arity of the tree. const H: usize = 3; const A: usize = 2;

let mut tree = Tree::::new();

// No elements have been inserted so the root is the empty subtree. asserteq!(*tree.root(), U8::EMPTYSUBTREE);

tree.insert(4, 21); tree.insert(7, 21);

// After elements have been inserted, the root will be modified. assert_eq!(*tree.root(), U8(42)); ```

An implementation of a Merkle tree using the blake3 hash algorithm is included as an example.

Another implementation of a Merkle tree with the poseidon252 hash and the creation of the opening proof in zero-knowledge using PLONK is included as a member of this workspace poseidon_merkle.

Benchmarks

Benchmarks are also included and can be run using:

For the blake3 tree: shell cargo bench

For the poseidon tree: shell cargo bench -p poseidon-merkle

For the opening proof creation in zero-knowledge: shell cargo bench -p poseidon-merkle --features zk

This requires a nightly toolchain.

Implementations

A merkle tree using the poseidon hash function for aggregation and plonk to generate an opening proof in zero-knowledge can be found in the same workspace under 'poseidon-merkle'.

License

This project is licensed under the Mozilla Public License, version 2.0. See the license file for more details.