Sparse Merkle tree
Sparse Merkle tree implementation in Rust.
A sparse Merkle tree is a data structure useful for storing a key/value map where every leaf node of the tree contains the cryptographic hash of a key/value pair and every non leaf node contains the concatenated hashes of its child nodes. Sparse Merkle trees provides a secure and efficient verification of large data sets and they are often used in peer-to-peer technologies. This implementation is an optimized version of the traditional sparse Merkle tree and it is based on the concepts expressed in the papers and resources below.
## References
1. Rasmus Dahlberg, Tobias Pulls and Roel Peeters. _Efficient Sparse Merkle Trees: Caching Strategies and Secure (Non-)Membership Proofs_. Cryptology ePrint Archive: Report 2016/683, 2016. https://eprint.iacr.org/2016/683.
2. Faraz Haider. _Compact sparse merkle trees_. Cryptology ePrint Archive: Report 2018/955, 2018. https://eprint.iacr.org/2018/955.
3. Jordi Baylina and Marta Bellés. _Sparse Merkle Trees_. https://docs.iden3.io/publications/pdfs/Merkle-Tree.pdf.
4. Vitalik Buterin Fichter. _Optimizing sparse Merkle trees_. https://ethresear.ch/t/optimizing-sparse-merkle-trees/3751.
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## 🛠 Install
You can install `zk-kit-smt` crate with `cargo`:
```bash
cargo add zk-kit-smt
```
## 📜 Usage
```rust
use zk_kit_smt::smt::{Key, Node, Value, SMT};
fn hash_function(nodes: Vec) -> Node {
let strings: Vec = nodes.iter().map(|node| node.to_string()).collect();
Node::Str(strings.join(","))
}
fn main() {
// Initialize the Sparse Merkle Tree with a hash function.
let mut smt = SMT::new(hash_function, false);
let key = Key::Str("aaa".to_string());
let value = Value::Str("bbb".to_string());
// Add a key-value pair to the Sparse Merkle Tree.
smt.add(key.clone(), value.clone()).unwrap();
// Get the value of the key.
let get = smt.get(key.clone());
assert_eq!(get, Some(value));
// Update the value of the key.
let new_value = Value::Str("ccc".to_string());
let update = smt.update(key.clone(), new_value.clone());
assert!(update.is_ok());
assert_eq!(smt.get(key.clone()), Some(new_value));
// Create and verify a proof for the key.
let create_proof = smt.create_proof(key.clone());
let verify_proof = smt.verify_proof(create_proof);
assert!(verify_proof);
// Delete the key.
let delete = smt.delete(key.clone());
assert!(delete.is_ok());
assert_eq!(smt.get(key.clone()), None);
}
```