cipher block chain (DES) (CBC)

Cipher Block Chain(CBC) is an encryption method. In this block cipher, a data block of plaintext to be ciphered is linked to the previous text block by an XOR operation before being encrypted with an encryption algorithm such as the DES algorithm.

Thus, there is a dependency of the cipher blocks on all preceding cipher blocks. The concatenation of the data blocks means that they cannot be changed, swapped or deleted without this being detected.

Block cipher process

For this concatenation process to work for the first block to be encrypted, an initial value agreed on both sides, the initialization vector( IV), is required. This initialization vector replaces the feedback-encrypted preceding block in the first step.

CBC modules

There are two different CBC methods: The CBC- MAC (Message Authentication Code), in which a MAC code is constructed using a block cipher, and the CBC mode, in which a block is XORed with the previous, already ciphered block before encryption.