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

PART 1 -

CODE -

# Taking plain text and key as input from the user
plain_text = input("Enter Plain Text: ")
key = int(input("Enter key: "))
# Initializing cipher text with empty string
cipher_text = ""
# Iterating over each character of plain text
for i in range(len(plain_text)):
letter = plain_text[i]
# Encrypting uppercase characters
if letter.isupper():
cipher_text += chr((ord(letter) - 65 + key) % 26 + 65)
# Encrypting lowercase characters
else:
cipher_text += chr((ord(letter) - 97 + key) % 26 + 97)
# Displaying plain text and encrypted text
print("\n\nPlain Text: ", plain_text)
print("\nEncrypted Text: ", cipher_text)

SCREENSHOT -

PART 2 -

CODE -

# Taking plain text and key as input from the user
plain_text = input("Enter Plain Text: ")
key = input("Enter key: ")

# Initializing generated key with key
gen_key = key
# Checking if length of key is equal to length of plain text or not
if len(gen_key) != len(plain_text):
# Generating key in a cyclic manner until its length is equal to length of plain text
for i in range(len(plain_text) - len(key)):
gen_key += key[i % len(key)]

# Initializing cipher text with empty string
cipher_text = ""
# Iterating over each character of plain text
for i in range(len(plain_text)):
# Converting into letter number between 0-25
letter_num = (ord(plain_text[i]) + ord(gen_key[i])) % 26
# Converting into ASCII characters
if plain_text[i].islower():
cipher_text += chr(ord('A') + letter_num).lower()
else:
cipher_text += chr(ord('A') + letter_num)

# Displaying plain text and encrypted text
print("\n\nPlain Text: ", plain_text)
print("\nEncrypted Text: ", cipher_text)

SCREENSHOT -

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