BIS MICRO PROJECT
AN MICRO PROJRCT REPORT ON
ENCRYPTION & DECRYPTION USING CAESAR
CIPHER
Submitted by
KASHISH MAHOVIA (216300307006)
KARINA SHARMA (226300307120 )
PRUTHA PANCHAL (226300307078)
Student of
Diploma In Engineering
in
computer Department
Project Overview:
The project will consist of:
A Python program to encrypt and decrypt messages.
A simple user interface (command-line) where the user can input a message and choose
to either encrypt or decrypt it using a key (shift value).
Encryption Algorithm - Caesar Cipher:
Encryption: The plaintext is shifted by a key value. For example, if the key is 3, 'A'
becomes 'D', 'B' becomes 'E', and so on.
Decryption: The ciphertext is shifted in the opposite direction by the same key to retrieve
the original message.
CODE(python):
# Caesar Cipher Encryption and Decryption
def encrypt(plaintext, key):
"""Encrypts the plaintext using Caesar Cipher with a given key."""
ciphertext = ''
for char in plaintext:
# Encrypt only alphabets (both uppercase and lowercase)
if char.isalpha():
shift = key % 26 # Ensure key is within the alphabet range
start = ord('A') if char.isupper() else ord('a')
encrypted_char = chr(start + (ord(char) - start + shift) % 26)
ciphertext += encrypted_char
else:
# Non-alphabet characters remain unchanged
ciphertext += char
return ciphertext
def decrypt(ciphertext, key):
"""Decrypts the ciphertext using Caesar Cipher with a given key."""
plaintext = ''
for char in ciphertext:
# Decrypt only alphabets (both uppercase and lowercase)
if char.isalpha():
shift = key % 26 # Ensure key is within the alphabet range
start = ord('A') if char.isupper() else ord('a')
decrypted_char = chr(start + (ord(char) - start - shift) % 26)
plaintext += decrypted_char
else:
# Non-alphabet characters remain unchanged
plaintext += char
return plaintext
def main():
print("Welcome to Caesar Cipher Encryption/Decryption")
while True:
# Menu for the user to choose between encryption or decryption
choice = input("\nChoose an option:\n1. Encrypt a message\n2. Decrypt a message\n3.
Exit\nEnter your choice (1/2/3): ")
if choice == '1':
message = input("\nEnter the message to encrypt: ")
key = int(input("Enter the encryption key (an integer): "))
encrypted_message = encrypt(message, key)
print(f"Encrypted message: {encrypted_message}")
elif choice == '2':
message = input("\nEnter the message to decrypt: ")
key = int(input("Enter the decryption key (an integer): "))
decrypted_message = decrypt(message, key)
print(f"Decrypted message: {decrypted_message}")
elif choice == '3':
print("Exiting the program...")
break
else:
print("Invalid choice, please try again.")
if __name__ == "__main__": main()
How It Works:
Encrypt Function:
The encrypt() function shifts each letter of the input message by the specified key
(integer). The shift is done modulo 26 to keep the result within the alphabet
range.
Non-alphabet characters (such as spaces, punctuation) remain unchanged.
Decrypt Function:
The decrypt() function works similarly but shifts the letters back in the opposite
direction to recover the original message.
Main Program:
The user is presented with a menu to choose between encrypting a message,
decrypting a message, or exiting the program.
Depending on the user's choice, they are prompted to input the message and key
(shift value).
OUTPUT SCREENSHORT :
