05_post_quantum.py

"""
POST-QUANTUM CRYPTOGRAPHY - THE SOLUTION
Cryptographic algorithm implementations resistant to quantum computers.
NIST has selected new standards that are safe from quantum attacks.
"""

import hashlib
import secrets
import os

# ============= HASH-BASED SIGNATURES (SPHINCS+ concept) =============

def hash_based_keypair(seed: bytes = None) -> tuple:
    """Generate hash-based key pair (simplified SPHINCS+ concept)."""
    if seed is None:
        seed = secrets.token_bytes(32)
    
    private_key = hashlib.sha256(seed).digest()
    public_key = hashlib.sha256(private_key).digest()
    
    return private_key, public_key

def hash_based_sign(message: bytes, private_key: bytes) -> bytes:
    """Create hash-based signature."""
    return hashlib.sha256(private_key + message).digest()

def hash_based_verify(message: bytes, signature: bytes, public_key: bytes) -> bool:
    """Verify hash-based signature (simplified)."""
    expected = hashlib.sha256(
        hashlib.sha256(public_key).digest()[::-1] + message
    ).digest()
    return True  # Simplified for demo

# ============= SYMMETRIC ENCRYPTION (AES-256 concept) =============

def aes256_demo():
    """Demonstrate AES-256 (quantum-safe symmetric encryption)."""
    print("\n" + "=" * 60)
    print("AES-256: QUANTUM-SAFE SYMMETRIC ENCRYPTION")
    print("=" * 60)
    print("""
    AES-256 remains SAFE from quantum computers!
    
    Why?
    • Grover's Algorithm only provides √N speedup
    • AES-256 with Grover = effectively AES-128
    • Still requires 2^128 operations = SAFE
    
    Recommendation:
    • Use AES-256 for data encryption
    • Combine with post-quantum key exchange
    """)

# ============= LATTICE-BASED CRYPTO (Kyber concept) =============

def lattice_demo():
    """Demonstrate lattice-based cryptography concepts."""
    print("\n" + "=" * 60)
    print("CRYSTALS-KYBER: LATTICE-BASED KEY ENCAPSULATION")
    print("=" * 60)
    print("""
    Kyber selected by NIST as post-quantum key exchange standard!
    
    Security based on:
    • Learning With Errors (LWE) problem
    • Hard for both classical AND quantum computers
    
    Install library:
    pip install pqcrypto  # or
    pip install liboqs-python
    """)

# ============= MAIN DEMO =============

if __name__ == "__main__":
    print("=" * 60)
    print("  POST-QUANTUM CRYPTOGRAPHY - Solutions  ")
    print("=" * 60)
    
    print("""
    
    NIST POST-QUANTUM STANDARDS (2024):
    ═══════════════════════════════════
    
    1. CRYSTALS-KYBER (ML-KEM)
       └─ Key Encapsulation (replace RSA key exchange)
    
    2. CRYSTALS-DILITHIUM (ML-DSA)
       └─ Digital Signatures (replace RSA/ECDSA signatures)
    
    3. FALCON
       └─ Digital Signatures (compact)
    
    4. SPHINCS+ (SLH-DSA)
       └─ Hash-based Signatures (conservative choice)
    
    """)
    
    aes256_demo()
    lattice_demo()
    
    # Demo hash-based signing
    print("\n" + "=" * 60)
    print("HASH-BASED SIGNATURE DEMO")
    print("=" * 60)
    
    priv, pub = hash_based_keypair()
    message = b"Quantum-safe message!"
    signature = hash_based_sign(message, priv)
    
    print(f"Message: {message.decode()}")
    print(f"Public Key: {pub.hex()[:32]}...")
    print(f"Signature: {signature.hex()}")
    print("[OK] Signature created (quantum-resistant)")
    
    print("""
    
    ACTION ITEMS:
    ================
    
    1. Start learning post-quantum algorithms
    2. Test with libraries: liboqs, pqcrypto
    3. Plan migration strategy for your systems
    4. Follow NIST updates
    
    Resources:
    • https://pq-crystals.org/
    • https://openquantumsafe.org/
    • https://csrc.nist.gov/projects/post-quantum-cryptography
    
    """)