Describe in detail how the CBC-MAC mode works . Do not just paste formulas in yo
ID: 3838923 • Letter: D
Question
Describe in detail how the CBC-MAC mode works . Do not just paste formulas in your paper; rather, give a high - level, readable English description of the operations of the mode. One good approach here is to use our hypothetical communicators, Alice and Bob, going through the procedures of message construction, transmission, decryption, and validation for one complete authenticated message. S upplement the description with your own intuitions and an alysis of how these operations work to ensure different aspects of secure communication. You don’t need to use a lot of math in this portion; rather, strive to present as clearly as possible an intuitive understanding of the protocol
Explanation / Answer
Cipher Block Chaining Message Aunthentication Code is a technique in cryptography for constructing a message authentication code from a block cipher. Cipher is an algorithm which encrypts and decrypts by well defined steps.
Block cipher is a symmetric key cipher which operates on blocks and have no change in transmission throughout the signal. To ensure an encrypted message from vulnerabilities it is needed an authentication code such as CBC-MAC.
Assume Bob sends a message through CBC-MAC code to Alice. The message is encrypted with some block cypher algorithm in CBC mode and create a chain of blocks. CBC is one of the mode of operation of block cypher in which it uses Initial vector of certain length. This makes the chain of blocks such that each block depends upon the encrytion of the previous block.
This encryption is done by means of XOR operation between the cipher blocks. i.e., each plain text block is XORed with the immediately previous ciphertext block.
This interdependence ensures that any change that made to any of the plain text bits will cause the final encrypted block to make changes in the message that it cannot be predicted without the cipher key.
The key is provided to the alice and if any attack occurs the message then changes into unpredicatble manner and by using the key she can read the code.