Expert 1: ⏱️ Side-Channel Attacks - Mencuri Kunci Lewat Waktu Eksekusi

cd ~ && mkdir crypto-exp1 && cd crypto-exp1

python3 << 'PYEOF'
import time, string, sys

# === VULNERABLE: Timing-dependent password check ===
def check_password_vuln(stored, attempt):
    """Vulnerable: returns early when character mismatch!"""
    if len(stored) != len(attempt):
        return False
    for i in range(len(stored)):
        if stored[i] != attempt[i]:
            return False  # ← Returns INSTANTLY!
        time.sleep(0.001)  # simulate work
    return True

# === SECURE: Constant-time password check ===
def check_password_secure(stored, attempt):
    """Secure: always takes same time regardless of match position"""
    if len(stored) != len(attempt):
        return False
    result = 0
    for i in range(len(stored)):
        result |= ord(stored[i]) ^ ord(attempt[i])
    return result == 0

# === ATTACK: Timing Attack ===
real_password = "abcdefgh"
print(f"Real password: {real_password}")
print()

print("=== Timing Attack ==*")
print("Mengukur waktu untuk setiap tebakan byte pertama...")
print()

# Tebak byte pertama
timings = []
for c in string.printable[:95]:
    attempt = c + "a" * 7  # tebak byte 1, sisanya dummy
    start = time.perf_counter_ns()
    check_password_vuln(real_password, attempt)
    elapsed = time.perf_counter_ns() - start
    timings.append((elapsed, c))

# Urutkan berdasarkan waktu (paling lama = byte benar!)
timings.sort(reverse=True)
print(f"Byte pertama: '{timings[0][1]}' (waktu: {timings[0][0]} ns) - benar!")
print(f"Byte kedua:   '{timings[1][1]}' (waktu: {timings[1][0]} ns)")
print()
print("✅ Dengan mengukur timing, attacker bisa menebak")
print("   password byte-per-byte dalam ~26 percobaan per byte!")
print("   Total: 26 × 8 = 208 percobaan (vs 26^8 brute force)")
print()

# Secure version - timing constant
print("=== Constant-Time Verification ==*")
print("Dengan check_password_secure(), waktu konstan")
print("untuk setiap input - tidak ada informasi bocor via timing!")
check_password_secure(real_password, "a" * 8)  # warmup
PYEOF