Question

Cryptography and Applications

1. Write Python program to implement Caesar’s Cipher. Take user input to get plain text and key.

2.  Write a Python program to implement Vignere Cipher. Take user input to get plain text and key.

TRY TO MAKE IT AS EASY AS YOU CAN.

Answer 1

1.

'''
"program to implement ceasar's cipher"

def encrypt(string, shiftkey):

cipher = ''
for char in string:
if char == ' ':
cipher = cipher + char
elif char.isupper():
cipher = cipher + chr((ord(char) + shiftkey - 65) % 26 + 65) #Encrypt uppercase characters in plain text
else:
cipher = cipher + chr((ord(char) + shiftkey - 97) % 26 + 97) #Encrypt lowercase characters in plain text
  
return cipher
  
print("program to implement ceasar's cipher")
text = input("enter string: ")
skey = int(input("enter shift number: ")) #number used to shift character
print("original string: ", text)
print("after encryption: ", encrypt(text, skey)) # function call inside print statement"

output:

program to implement ceasar's cipher                                                                            

enter string: welcome to programming                                                                            

enter shift number: 3                                                                                           

original string:  welcome to programming                                                                        

after encryption:  zhofrph wr surjudpplqj  

"Explanation for ceasar' cipher:

• In Caesar Cipher each letter of plain text is replaced by a letter with some fixed number of positions down with alphabet. We need to pass the text to be encrypted using Caesar cipher along with the shift key length (fixed difference) then to encrypt our data; we have to replace each letter in the text by some other letter at a fixed difference.
• If we give key length as “2” then letter “t” will be changed to “v”, “h” will be changed to “j” and so on."
• In our program have used text as ^“welcome to programming  “ which encrypted as “zhofrph wr surjudpplqj “