Design and analysis of AES-CBC mode for high security applications

The challenge in securizing communications networks is to obtain flexible means able to deal with the intensive computation needed by the cryptography algorithms. A representative example of this algorithm is the Rijndael The 128-bit AES block cipher combines a 128-bit key and a 128-bit plaintext data block to get a 128-bit block of cipher text data. The Electronic Code Book (ECB) mode is the simplest encryption mode. In this mode, the message is split into blocks and each one is separately encrypted. So, therefore identical plaintext blocks are encrypted to identical cipher text blocks. This drawback generates vulnerabilities like modification of ciphered messages. In order to solve this problem, more complex modes of operation combine the data of the previous ciphered blocks and use Initialization Vectors (IV) to make each ciphered message unique. The AES Cipher-Block Chaining (CBC) mode includes these features. Before encrypting a block, it is XORed with the cipher text of the previous cipher text block. In this paper, the design and analysis of AES-CBC mode is presented to find the fault during the encryption process. Simulation is performed to analyze the chip size reduction.