Cipher Block Chaining (CBC)

• Cipher block chaining (CBC) is a mode of operation of block cipher.

• CBC uses what is known as an initialization vector (IV) of a certain length to start the process.

• Each previous ciphertext block is chained with current  plain text block.

• It is mainly used for bulk data encryption and authentication.

• A ciphertext block depends on all blocks before it , thus any change to a block affects all the following blocks.

• If an attacker gets hold of the initialization vector, they can change the bits of the first block, thus IV should be a fixed value or derived in a way hard to manipulate.

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