JavaBlockchainData StructuresCryptography
Merkle Tree Implementation
A Java implementation of Merkle Trees for efficient data verification, commonly used in blockchain and distributed systems.
Overview
A production-ready Merkle Tree implementation in Java, designed for efficient data integrity verification. Merkle trees are fundamental to blockchain technology, enabling quick verification of large datasets.
What is a Merkle Tree?
A Merkle tree is a binary tree where:
- Leaf nodes contain hashes of data blocks
- Non-leaf nodes contain hashes of their children
- The root hash represents the entire dataset
Key Features
- Proof Generation: Create compact proofs for any element
- Proof Verification: Verify inclusion without full dataset
- Tree Construction: Efficient bottom-up building
- Multiple Hash Algorithms: Support for SHA-256, Keccak, etc.
Implementation
Node Structure
public class MerkleNode {
private final byte[] hash;
private final MerkleNode left;
private final MerkleNode right;
public static MerkleNode createLeaf(byte[] data) {
return new MerkleNode(
HashUtils.sha256(data),
null,
null
);
}
public static MerkleNode createParent(MerkleNode left, MerkleNode right) {
byte[] combined = ByteUtils.concat(left.hash, right.hash);
return new MerkleNode(
HashUtils.sha256(combined),
left,
right
);
}
}
Proof Generation
public List<ProofElement> generateProof(int index) {
List<ProofElement> proof = new ArrayList<>();
// Traverse from leaf to root, collecting sibling hashes
// Each element includes the sibling hash and position (left/right)
return proof;
}
Use Cases
- Blockchain: Transaction verification in Bitcoin/Ethereum
- Git: File integrity verification
- Distributed Databases: Synchronization protocols
- Certificate Transparency: Audit logs
Performance
- Construction: O(n) time complexity
- Proof Generation: O(log n)
- Verification: O(log n)
- Space: O(n) for tree, O(log n) for proofs
Applications in My Work
This implementation has been used in:
- Cryptocurrency exchange proof of reserves
- Distributed system state synchronization
- Data integrity verification systems