In Cipher Block Chaining (CBC) mode, the encryption process is bootstrapped by inputting an IV that is XOR'd with the first block of plaintext. The result of the XOR operation is input to the cipher to produce the first block of encrypted ciphertext, the value of which is then XOR'd with the next block of plaintext. The result of this XOR goes through the cipher again. The process continues until all of the blocks of plaintext have been processed. This construction ensures that two identical blocks of plaintext will not have the same ciphertext representation. Thus, traffic analysis (the ability to discern what the plaintext was from its ciphertext) is far more difficult to perform by adversaries.
Other block chaining ...
