How to fix this python code to do this:

$1.$ Your program should be able to replace part of one message with part of the other message. The exercise suggests to begin by replacing the last block of the new message with the last block of the older message. This probably does not decrypt exactly like you thought.

$2.$ Consider making changes to the message format to make it easier to switch one block for another. For example, you may want to change the format of the date so that it uses the same number of digits for all dates.

$3.$Modify your program so that it asks the user which part of the message to change $($From Who, To Whom, Date, or Meeting place$).$

$4.$ Your program should take the user input and swap out the respective block$($s$)$ of one message with the respective block$($s$)$ from another message. The newly created ciphertext should decrypt to something that looks like a real message.

This is the prompt: "Take two different ciphertexts from Alice to Bob with different meeting instructions on different dates. Splice the ciphertext from the body of the first message into the body of the second message. that is$,$ start by replacing the last block of the newer message with the last block $($or blocks if it was longer$)$ of the previous message. Does the message decrypt? did you change where Bob goes to meet Alice?"

The code:

from Crypto.Cipher import AES

from Crypto.Random import get$\_$random$\_$bytes

from Crypto.Util.Padding import pad, unpad

# Key for encryption

key $=$ get$\_$random$\_$bytes$(16)$

# Encrypt function using AES

def encrypt$\_$message$($message$)$:

cipher $=$ AES.new$($key$,$ AES.MODE$\_$CBC$)$

ciphertext $=$ cipher.encrypt$($pad$($message$.$encode$(),$ AES.block$\_$size$))$

return ciphertext, cipher.iv

# Decrypt function using AES

def decrypt$\_$message$($ciphertext$,$ iv$)$:

cipher $=$ AES.new$($key$,$ AES.MODE$\_$CBC$,$ iv$)$

decrypted$\_$message $=$ unpad$($cipher$.$decrypt$($ciphertext$),$ AES.block$\_$size$).$decode$()$

return decrypted$\_$message

# Function to switch message parts

def switch$\_$message$\_$parts$($message$1,$ message$2,$ part$\_$to$\_$change$)$:

# Split messages into parts

parts$1=$ message$1.$split$(\text{'}$

$\text{'})$

parts$2=$ message$2.$split$(\text{'}$

$\text{'})$

# Switch the respective values

if part$\_$to$\_$change $==$ "From Who":

parts$1[0]=$ parts$2[0]$

parts$2[0]=$ parts$1[0]$ # Swap the 'From Who' parts

elif part$\_$to$\_$change $=="$To Whom":

parts$1[1]=$ parts$2[1]$

parts$2[1]=$ parts$1[1]$ # Swap the $\text{'}$To Whom' parts

elif part$\_$to$\_$change $==$ "Date":

parts$1[2]=$ parts$2[2]$

parts$2[2]=$ parts$1[2]$ # Swap the 'Date' parts

elif part$\_$to$\_$change $==$ "Meeting place":

parts$1[3]=$ parts$2[3]$

parts$2[3]=$ parts$1[3]$ # Swap the 'Meeting place' parts

# Return the updated parts

new$\_$message$1=\text{'}$

$\text{'}.$join$($parts$1)$

new$\_$message$2=\text{'}$

$\text{'}.$join$($parts$2)$

return new$\_$message$1,$ new$\_$message$2$

# Example messages

message$1=$ "Alice

Bob

$2024-06-10$

Park"

message$2=$ "Alice

Bob

$2024-06-15$

Restaurant"

# Encrypt messages

ciphertext$1,$ iv$1=$ encrypt$\_$message$($message$1)$

ciphertext$2,$ iv$2=$ encrypt$\_$message$($message$2)$

# Switch values

part$\_$to$\_$change $=$ input$("$Which part of the message to switch? $($From Who, To Whom, Date, or Meeting place$)$: $")$

# Decrypt messages before switching

decrypted$\_$message$1=$ decrypt$\_$message$($ciphertext$1,$ iv$1)$

decrypted$\_$message$2=$ decrypt$\_$message$($ciphertext$2,$ iv$2)$

# Switch parts and reconstruct messages

new$\_$message$1,$ new$\_$message$2=$ switch$\_$message$\_$parts$($decrypted$\_$message$1,$ decrypted$\_$message$2,$ part$\_$to$\_$change$)$

# Encrypt the $*$NEW$*$ messages

ciphertext$\_$new$1,$ iv$\_$new$1=$ encrypt$\_$message$($new$\_$message$1)$

ciphertext$\_$new$2,$ iv$\_$new$2=$ encrypt$\_$message$($new$\_$message$2)$

# Print new messages

print$("$New Message $1$:$")$

print$($new$\_$message$1)$

print$("$New Message $2$:$")$

print$($new$\_$message$2)$

decrypted$\_$message$\_$new$1=$ decrypt$\_$message$($ciphertext$\_$new$1,$ iv$\_$new$1)$

decrypted$\_$message$\_$new$2=$ decrypt$\_$message$($ciphertext$\_$new$2,$ iv$\_$new$2)$

print$("$

Decrypted New Message $1$:$")$

print$($decrypted$\_$message$\_$new$1)$

print$("$Decrypted New Message $2$:$")$

print$($decrypted$\_$message$\_$new$2)$