This repository contains a didactic Jupyter notebook on the AES-128 block cipher, focused on understanding how the algorithm works internally and how its security properties emerge.

• AES internal structure (SubBytes, ShiftRows, MixColumns, AddRoundKey)
• Key expansion overview
• Modes of operation (ECB, CBC, CFB, OFB)
• Simple experiments on diffusion and confusion using bit flips and Hamming distance