Question: 1.Consider the Basic CBC-MAC in module 4.3, with a block cipher having a 256-bit key and 128-bit block length to MAC a 1024-bit message. How

1.Consider the Basic CBC-MAC in module 4.3, with a block cipher

1.Consider the Basic CBC-MAC in module 4.3, with a block cipher having a 256-bit key and 128-bit block length to MAC a 1024-bit message. How many evaluations of the block cipher will be performed to calculate the tag? Explain. [Assume there is no padding]

2. How will your answer to question 1 change if the key size is reduced to 128 bits? Explain.

Characteristics Need to know message length at the beginning FIGURE 4.2: A version of CBC-MAC secure for authenticating arbitrary-length messages

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