Question $4$ Encryption $[40$ marks$]$

Develop a program named MAC, which simulates a Message Authentication Code. This

program should accept four parameters: the option $("$gen$"$ or "verify"$),$ the name of the AES

file, the input file, and the MAC file $($for generation or verification$).$

The program will read an AES key that has been generated by the provided program,

RandomAESKeyGen. If the chosen option is "gen", it will calculate the SHA$-1$ hash of the

input file, encrypt this hash using the AES key, and write the encrypted data to the specified

MAC file. If the chosen option is "verify", it will again calculate the SHA$-1$ hash of the input

file and encrypt it using the AES key. The result will then be compared with the content of the

specified MAC file. If the two match, 'Verification: Successful!$\text{'}$ will be displayed; if not,

'Verification: Failed!$\text{'}$ will be displayed. For both options, the digest is displayed in base$64$

format.

The RandomAESKeyGen program is provided for you, which generates a random AES key

and writes to the file specified in the input parameter.

Below are sample outputs from compiling and running the program.

$>$ javac a$2\backslash$RandomAESKeyGen$.$java

$>$ javac a$2\backslash$MAC$.$java

$>$ java a$2.$RandomAESKeyGen my$\_$aes.key

$>$ java a$2.$MAC gen my$\_$aes.key notes.txt notes.txt$.$mac

The digest is $($in base$64$ format$)$: JkSYEkH$5$rRBIlayDdI$1$SuGI$4$Qto$=$

$>$ java a$2.$MAC verify my$\_$aes.key notes.txt notes.txt$.$mac

The digest is $($in base$64$ format$)$: JkSYEkH$5$rRBIlayDdI$1$SuGI$4$Qto$=$

Verification: Successful!

If the notes.txt is modified

$>$ java a$2.$MAC verify my$\_$aes.key notes.txt notes.txt$.$mac

The digest is $($in base$64$ format$)$: Lk$/$Oa$44$NojNXCBPcTwSRyzttIGM$=$

Verification: Failed!

If the mode is incorrect

$>$ java a$2.$MAC verify my$\_$aes.key notes.txt notes.txt$.$mac

Incorrect modeDevelop a program named MAC, which simulates a Message Authentication Code. This

program should accept four narameters: the option $("$gen$"$ or "verify"$),$ the name of the $\frac{?}{\text{b}\text{a}\text{r}}((\frac{?}{\text{b}\text{a}\text{r}}(A))ES)$

file, the input file, and the $\frac{?}{\text{b}\text{a}\text{r}}(\frac{?}{\text{b}\text{a}\text{r}}(M))AC$ file $($for generation or verification$).$

The program will read an AES key that has been generated by the provided program,

RandomAESKeyGen. If the chosen option is "gen", it will calculate the SHA$-1$ hash of the

input file, encrypt this hash using the AES key, and write the encrypted data to the specified

MAC file. If the chosen option is "verify", it will again calculate the SHA$-1$ hash of the input

file and encrypt it using the AES key. The result will then be compared with the content of the

specified MAC file. If the two match, 'Verification: Successful!$\text{'}$ will be displayed; if not,

'Verification: Failed!$\text{'}$ will be displayed. For both options, the digest is displayed in base $64$

format.

The RandomAESKeyGen program is provided for you, which generates a random AES key

and writes to the file specified in the input parameter.

Below are sample outputs from compiling and running the program.javac a$2\backslash$MAC$.$javajava a$2.$MAC gen my$\_$aes.key notes.txt notes.txt$.$mac

The digest is $($in base$64$ format$)$: JkSYEkH$5$rRBIlayDdI$1$SuGI$4$Qto$=$The digest is $($in base$64$ format$)$: JkSYEkH$5$rRBIlayDdI$1$SuGI$4$Qto$=$

Verification: Successful!

If the notes.txt is modifiedThe digest is $($in base$64$ format$)$: Lk$/$Oa$44$NojNXCBPCTwSRyzttIGM$=$

Verification: Failed!

If the mode is incorrect

$>$ java a$2.$MAC verify my$\_$aes.key notes.txt notes.txt$.$mac

Incorrect mode