Symmetric Key Algorithms — AES & DES in Depth

This lesson dives into block cipher architectures, exploring how AES operates across 128, 192, and 256-bit key lengths. We'll work through the SubBytes, ShiftRows, MixColumns, and AddRoundKey transformations step by step, then compare AES against its predecessor DES and examine why DES is now considered cryptographically broken.

By the end of this lesson you will be able to:

• Explain the structure and round function of AES-128
• Compare AES key schedule against DES Feistel structure
• Identify common AES implementation vulnerabilities
• Apply CBC, CTR, and GCM modes appropriately