feat(smt): add smt crate (#41)

* feat(smt): add `smt` crate

* docs(smt): add README and examples

* docs(smt): fix README links

* fix(smt): fix spelling error

Co-authored-by: sripwoud <[email protected]>

* docs(smt): fix format

* docs(smt): fix format

* refactor(smt): improve error handling

* refactor(smt): implement `FromStr` for `Node`

* docs(smt): update usage

* docs(smt): update example

---------

Co-authored-by: sripwoud <[email protected]>

crates/smt/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "zk-kit-smt"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+description = "Sparse Merkle Tree"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+num-bigint = "0.4.6"

crates/smt/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2024 Pinco
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

crates/smt/README.md

@@ -0,0 +1,90 @@
+<p align="center">
+    <h1 align="center">
+        Sparse Merkle tree
+    </h1>
+    <p align="center">Sparse Merkle tree implementation in Rust.</p>
+</p>
+
+<p align="center">
+    <a href="https://github.com/privacy-scaling-explorations/zk-kit">
+        <img src="https://img.shields.io/badge/project-zk--kit-blue.svg?style=flat-square">
+    </a>
+    <a href="https://github.com/privacy-scaling-explorations/zk-kit.rust/tree/main/packages/smt/LICENSE">
+        <img alt="License" src="https://img.shields.io/crates/l/zk-kit-smt?style=flat-square">
+    </a>
+    <a href="https://crates.io/crates/zk-kit-smt">
+        <img alt="Version" src="https://img.shields.io/crates/v/zk-kit-smt?style=flat-square" />
+    </a>
+    <a href="https://crates.io/crates/zk-kit-smt">
+        <img alt="Downloads" src="https://img.shields.io/crates/d/zk-kit-smt?style=flat-square" />
+    </a>
+</p>
+
+<div align="center">
+    <h4>
+        <a href="https://appliedzkp.org/discord">
+            🗣️ Chat &amp; Support
+        </a>
+    </h4>
+</div>
+
+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.
+
+---
+
+## 🛠 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>) -> Node {
+    let strings: Vec<String> = 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);
+}
+```

crates/smt/examples/smt.rs

@@ -0,0 +1,37 @@
+use zk_kit_smt::smt::{Key, Node, Value, SMT};
+
+fn hash_function(nodes: Vec<Node>) -> Node {
+    let strings: Vec<String> = 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);
+}

crates/smt/src/lib.rs

@@ -0,0 +1,2 @@
+pub mod smt;
+mod utils;