AES (Advanced Encryption Standard)

AES nima?

AES — 2001 yilda NIST tomonidan standart sifatida qabul qilingan blok shifr. 128, 192 yoki 256 bitli kalit ishlatadi. Bugungi kunda Internet xavfsizligining asosi.

AES ishlash principi

Bu 4 qadam 10-14 marta (raund soni kalitga bog'liq) takrorlanadi.

AES rejimlari

ECB — Electronic Codebook (Xavfli!)

from Crypto.Cipher import AES
from Crypto.Util.Padding import pad, unpad

key = b"YELLOW SUBMARINE"  # 16 bayt = 128 bit

# Shifrlash
cipher = AES.new(key, AES.MODE_ECB)
plaintext = b"Hello World!!!!!"  # 16 bayt (blok o'lchami)
ciphertext = cipher.encrypt(plaintext)
print(ciphertext.hex())

# Deshifrlash
cipher = AES.new(key, AES.MODE_ECB)
decrypted = cipher.decrypt(ciphertext)
print(decrypted.decode())

# MUAMMO: bir xil plaintext → bir xil ciphertext!
# Shuning uchun ECB xavfli — naqsh ko'rinadi

CBC — Cipher Block Chaining (Yaxshiroq)

from Crypto.Random import get_random_bytes

key = get_random_bytes(16)
iv  = get_random_bytes(16)  # Initialization Vector

# Shifrlash
cipher = AES.new(key, AES.MODE_CBC, iv)
plaintext = b"Salom dunyo! Bu CBC rejimi testi!"
ciphertext = cipher.encrypt(pad(plaintext, AES.block_size))

# Deshifrlash
cipher = AES.new(key, AES.MODE_CBC, iv)
decrypted = unpad(cipher.decrypt(ciphertext), AES.block_size)
print(decrypted.decode())

CTR — Counter Mode (Zamonaviy)

from Crypto.Cipher import AES
from Crypto.Util import Counter

key = b"YELLOW SUBMARINE"
nonce = 0  # HECH QACHON bir xil nonce ni qayta ishlatmang!

ctr = Counter.new(128, initial_value=nonce)
cipher = AES.new(key, AES.MODE_CTR, counter=ctr)
ciphertext = cipher.encrypt(b"Salom CTR!")

# Xuddi shunday nonce bilan decrypt
ctr = Counter.new(128, initial_value=nonce)
cipher = AES.new(key, AES.MODE_CTR, counter=ctr)
plaintext = cipher.decrypt(ciphertext)
print(plaintext.decode())

CTF da AES hujumlari