XDC ZK Lab Guide | Learn Zero-Knowledge & Post-Quantum Cryptography

📑 Table of Contents

1. Introduction 2. The Quantum Threat 3. Zero-Knowledge Commitments 4. Hash-Based Signatures 5. Merkle Tree Proofs 6. Algorithm Comparison 7. Ethereum Foundation Research 8. XDC & The Future

1. Introduction

XDC ZK Lab is an educational platform for learning about two critical areas of modern cryptography:

🔒 Zero-Knowledge Proofs

Prove something is true without revealing WHY it's true. Used for privacy, voting, and scalability.

🛡️ Post-Quantum Cryptography

Cryptographic algorithms that remain secure against attacks from quantum computers.

2. The Quantum Threat

Current blockchain cryptography (ECDSA, BLS) relies on mathematical problems that quantum computers can solve efficiently using Shor's Algorithm.

⚠️ What's at Risk

When large-scale quantum computers arrive, they could:

Derive private keys from public keys
Forge digital signatures
Steal funds from any wallet whose public key is known

✅ What's Safe

Hash functions (Keccak-256, SHA-3) remain relatively secure. Quantum computers only reduce their effective security by half (Grover's algorithm).

Timeline

Experts estimate "Q-Day" (when quantum computers break ECDSA) could arrive between 2030-2040. However, blockchain data is permanent—an attacker could store encrypted data now and decrypt it later.

3. Zero-Knowledge Commitments

A commitment scheme lets you "lock in" a value without revealing it. Later, you can prove you committed to that exact value.

How It Works

commitment = hash(secret + salt)

// Later, to reveal:
verify: hash(revealed_secret + salt) == commitment

Using the Demo

Enter Your Secret

Type any value (e.g., your vote, a number, a password)

Note the Salt

A random salt is auto-generated. Save it—you'll need it to reveal later.

Create Commitment

Click to generate. Share the commitment hash (it reveals nothing about your secret).

Verify Later

To prove what you committed, provide the secret + salt. Anyone can verify.

💡 Real-World Use Cases

Voting — Commit to your vote, reveal after polls close
Auctions — Sealed bids that can't be changed
Games — Commit to moves in turn-based games
Randomness — Generate fair random numbers collaboratively

4. Hash-Based Signatures

Unlike ECDSA, hash-based signatures rely only on the security of hash functions—which remain quantum-safe.

How It Works (Simplified)

// Key Generation
private_key = random_bytes()
public_key = hash(private_key)

// Signing
signature = hash(private_key + message)

// Verification
verify: hash(derived_key + message) == signature

💡 Real Algorithms

Lamport Signatures — Original one-time signature
SPHINCS+ — NIST-standardized, stateless
XMSS — Stateful, very secure

Using the Demo

Generate Keypair

Creates a quantum-safe public/private key pair

Sign a Message

Enter any message and generate a signature

Verify Signature

Anyone with the public key can verify the signature is valid

5. Merkle Tree Proofs

Merkle trees let you prove an item belongs to a set without revealing the entire set. Foundation of ZK-rollups, airdrops, and state proofs.

Structure

         [Root Hash]
           /      \
      [Hash AB]  [Hash CD]
       /    \     /    \
   [A]    [B]  [C]    [D]

Proof Example

To prove "B" is in the tree, you only need:

Hash of A (sibling)
Hash of CD (uncle)
The root hash

This is O(log n) data instead of O(n)—very efficient for large sets!

Using the Demo

Build Tree

Enter items (one per line) and build the Merkle tree

Generate Proof

Enter an item to get its inclusion proof

Verify Proof

Given root + item + proof, verify inclusion

💡 Blockchain Use Cases

Airdrops — Prove you're on the whitelist
Rollups — Prove transaction inclusion
Light Clients — Verify state without full sync

6. Algorithm Comparison

Algorithm	Type	Classical	Quantum	Used In
ECDSA	Signature	✓ Safe	✗ Broken	BTC, ETH, XDC
BLS	Signature	✓ Safe	✗ Broken	ETH Validators
Keccak-256	Hash	✓ Safe	✓ 128-bit*	ETH Addresses
SPHINCS+	Signature	✓ Safe	✓ Safe	NIST Standard
Dilithium	Signature	✓ Safe	✓ Safe	NIST Standard
STARKs	ZK Proof	✓ Safe	✓ Safe	StarkNet
SNARKs	ZK Proof	✓ Safe	✗ Pairing-based	Zcash, zkSync

* Grover's algorithm halves effective hash security

7. Ethereum Foundation Research

The Ethereum Foundation is actively researching post-quantum solutions:

🔮 Roadmap Items

STARK Aggregation — Replace BLS signatures with quantum-safe STARKs
KZG Replacement — Swap polynomial commitments for hash-based
Account Abstraction — Enable any signature scheme per wallet
Emergency Hard Fork — Plan for quantum emergency scenario

Learn More

8. XDC & The Future

As an EVM-compatible chain, XDC will benefit from Ethereum's post-quantum research. Key considerations:

🔷 Preparation Steps

Monitor Ethereum's migration plans
Research lattice-based and hash-based alternatives
Consider Account Abstraction for flexible signatures
Educate developers and users on quantum risks

💡 Why Act Now?

Blockchain data is permanent. "Harvest now, decrypt later" attacks mean sensitive transactions today could be exposed decades from now. Early preparation is essential.