Write a program to do the enciphering. It should prompt the user for a message,

Question

Write a program to do the enciphering. It should prompt the user for a message, and print out both the entered message and its corresponding ciphertext.

Input. The message to be enciphered. Here is what a correct input should look like (the red text is what you type):

Output. The message to be enciphered and the corresponding ciphertext. Here is what the output corresponding to the above input should look like:

(note the double quotes around the plaintext and ciphertext).

Here is another example. The input is:

and the corresponding output is:

Now write a program to decipher the messages. Again, it should prompt the user for a ciphertext, and print out both the entered ciphertext and the corresponding plaintext.

Input. The message to be deciphered. Here is what a correct input should look like (the red text is what you type):

Output. The message to be deciphered and the corresponding plaintext. Here is what the output corresponding to the above input should look like:

(note the double quotes around the ciphertext and plaintext).

Here is another example. The input is:

and the corresponding output is:

Now we will combine the two parts you just did into a single program. This program asks the user to type

Explanation / Answer

# http://ideone.com/Wc4wXR

def encipher(msg):
   l = len(msg)
   cipher = ''
   for i in range(0,l,2):
       cipher = cipher+msg[i]
   for i in range(1,l,2):
       cipher = cipher+msg[i]
   return cipher

def decipher(cipher):
   l1 = len(cipher)
   l = int(l1/2)
   msg = ''
   for i in range(l):
       msg = msg+cipher[i]
       if l1%2 != 0:
           msg = msg+cipher[l+i+1]
       else:
           msg = msg+cipher[l+i]
   if l1%2 != 0:
       msg = msg+cipher[l]
   return msg

if __name__=='__main__':
   msg = raw_input('Enter plain text: ')
   print('Plain = "{0}"'.format(msg))
   print('Cipher = "{0}"'.format(encipher(msg)))
   msg = raw_input('Enter cipher text: ')
   print('Cipher = "{0}"'.format(msg))
   print('Plain = "{0}"'.format(decipher(msg)))

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