Block Cipher Fundamentals & Padding
Understand block size, PKCS7 padding, and cipher structure.
Welcome
Block ciphers encrypt fixed-size blocks. When plaintext doesn't fill a block, we need padding. In this lesson we master block cipher structure, padding schemes, and why they matter.
Block Size Review
AES uses 128-bit (16-byte) blocks. DES used 64-bit (8-byte) blocks. If plaintext is exactly 16 bytes, it's one block. 17 bytes requires two blocks.
All lessons in this course
- Block Cipher Fundamentals & Padding
- ECB vs CBC: Patterns & IVs
- CTR Mode & Stream-Cipher Behavior
- GCM & Authenticated Encryption