Tầng 2: Modern Symmetric

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Block ciphers: AES SPN structure, 4 phép biến đổi mỗi round; DES history.
Modes: ECB tệ (ECB-Penguin), CBC, CTR (parallel), GCM (authenticated encryption).
Hash: SHA-256 properties; birthday paradox; MD5/SHA1 đã chết.
MAC (HMAC fix length-extension), CSPRNG, KDF (PBKDF2/bcrypt/scrypt/Argon2).

Lesson 01

AES-128 SPN: SubBytes (S-box), ShiftRows, MixColumns (GF(2⁸)), AddRoundKey — animate từng round.

Lesson 02

ECB-Penguin (BAD), CBC chain + padding oracle, CTR + bit-flip attack, GCM authenticated encryption (AEAD).

Lesson 03

Preimage / 2nd-preimage / collision; SHA-256 walk-through; birthday paradox; MD5/SHA1 chết; length-extension attack.

Lesson 04

HMAC fix length-extension; LCG predict-next attack vs CSPRNG; PBKDF2/bcrypt/scrypt/Argon2 cost factor.