Expert 4: Homomorphic Encryption - Komputasi pada Data Terenkripsi

cd ~ && mkdir crypto-exp4 && cd crypto-exp4

python3 << 'PYEOF'
# === SIMPLE HOMOMORPHIC ENCRYPTION (Paillier-like) ===
# Untuk demo: menggunakan enkripsi additively homomorphic sederhana

import random

class SimpleHomomorphic:
    """Simplified additively homomorphic encryption (unsecure, for demo)"""
    def __init__(self):
        self.key = random.randint(1000, 9999)
    
    def encrypt(self, m):
        return m + self.key  # simplified: c = m + key
    
    def decrypt(self, c):
        return c - self.key
    
    def add(self, c1, c2):
        return c1 + c2  # E(m1) + E(m2) = E(m1 + m2)!

# === DEMO ===
crypto = SimpleHomomorphic()

# Alice punya dua angka
alice_salary = 50000
alice_bonus = 10000

# Alice encrypt
enc_salary = crypto.encrypt(alice_salary)
enc_bonus = crypto.encrypt(alice_bonus)

# Kirim ke cloud - server tidak tahu angka asli!
print("Data di cloud (encrypted):")
print(f"  Enc Salary: {enc_salary}")
print(f"  Enc Bonus:  {enc_bonus}")
print()

# Server melakukan komputasi pada data terenkripsi
print("Server menghitung total gaji (homomorphically)...")
enc_total = crypto.add(enc_salary, enc_bonus)  # E(salary) + E(bonus)
print(f"  Enc Total:  {enc_total}")
print()

# Alice decrypt hasilnya
total = crypto.decrypt(enc_total)
print(f"Alice decrypt: {total}")
print(f"✅ {alice_salary} + {alice_bonus} = {total}")
print()

# Demonstrasi: server tidak pernah lihat data asli!
print("=== Server tidak tahu apa-apa! ==*")
print(f"Server hanya lihat: {enc_salary}, {enc_bonus}, {enc_total}")
print(f"Server TIDAK TAHU: gaji Alice Rp 50.000!")
print()

# === Real-world comparison ===
print("=== Homomorphic Encryption Types ==*")
print(f"{'Type':<25} {'Supports':<30} {'Practical?'}")
print("-"*70)
print(f"{'Partially (PHE)':<25} {'Add atau Mul saja':<30} {'✅ Tahun 2000an'}")
print(f"{'Somewhat (SWHE)':<25} {'Add + Mul (terbatas)':<30} {'⚠️ Research'}")
print(f"{'Fully (FHE)':<25} {'Add + Mul (unlimited)':<30} {'⚠️ 2020s - slow'}")
print()
print("Contoh implementasi:")
print("  - Paillier: additively homomorphic")
print("  - ElGamal: multiplicatively homomorphic")
print("  - BFV/BGV: FHE (lattice-based)")
print("  - CKKS: FHE untuk floating point")
PYEOF