Illustrate CBCMAC for the message 123 with 1byte blocksSolut

Illustrate CBC-MAC for the message “123” with 1-byte blocks

Solution

Cipher block chaining message authentication code (CBC MAC) is based on the functionality of pseudorandom function.

In this CBC encryption, this technique is applies to a plain text block and cipher. Internally cbc uses initialization vector IV. Remember that Cbc is stateless so we call it as cbc stateless.

Cbc encryption algorithm :

N – [|M|/bl-bits]

If |M| does not belongs to {bl,2bl,3bl,…} now

M – M || 10^(bl-1-(|M|mod bl)) finalized

C0 – Intialization Vector IV – {0,1} raised to bl bits

For num =1 to n then do

Cnum – Encrypted (Cnum-1 + Mnum) close the loop

Return C – C0C1C2…Cn

In the given message 123

CBC with MAC by using this authenticate with a secret shared key. If the message 123 CBC mac is generating hex characters which is in 64 bit format.

Using 1 byte block

Message 123

Convert that into hex format is by using 1 byte block. AES Cipher Block Chaining (CBC) encryption we use an IV to make sure that the bits differ for the same message. In CBC-MAC the IV is set to zero, whereas with AES-CCM (Counter with CBC-MAC) the IV value is used to change the message digest.

Observe the algorithm: encrypted of message by using key is 55FE2982C1D2227B2687B1

MAC for the above message is 0FFB33725933D582