06 Block Cipher Modes

Block Ciphers can be used in a number of modes

1. Electronic codebook mode (ECB)
   • each block is encrypted individually.
   • encrypted blocks are assembled in the same order as the plain text blocks.
   • if blocks are repeated in the plain text, this is revealed by the cipher text.
2. Cipher Block Chaining Mode (CBC)
   • each block is XOR’d with the previous block.
   • starts with a random initialization vector (IV).
   • helps overcome replay attack.