CBC

A block cipher mode where each block is XORed with the previous ciphertext block.

CBC is a block cipher mode that XORs each plaintext block with the previous ciphertext block before encryption, so identical plaintext blocks produce different output and patterns are hidden. It requires a random initialization vector for the first block and processes blocks sequentially, which prevents parallel encryption. Because a single corrupted block affects decryption of adjacent blocks, and padding handling has enabled padding oracle attacks, authenticated modes such as GCM are now generally preferred over plain CBC.