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Author: PurpleVen

vignere_cipher.py

@@ -0,0 +1,45 @@
+'''Firstly, a key is generated with the help of a keyword if the length of
+the message is not equal to the keyword.'''
+def generateKey(string, key):
+    key = list(key)
+    if len(string) == len(key):
+        return (key)
+    else:
+        for i in range(len(string) - len(key)):
+            key.append(key[i % len(key)])
+    '''The join() method takes all items in an iterable and joins them into one string.'''
+    return ("".join(key))
+
+'''encryption() to encrypt the message which takes two arguments one is the message that needs to be encrypted and
+the second argument is the key that returns the encrypted text.'''
+def encryption(string, key):
+    encrypt_text = []
+    for i in range(len(string)):
+        '''In the encryption function the
+        message and key are added modulo 26'''
+        x = (ord(string[i]) + ord(key[i])) % 26
+        x += ord('A')
+        encrypt_text.append(chr(x))
+    return ("".join(encrypt_text))
+
+'''decryption function to decrypt the encrypted message. That takes two
+arguments one is the encrypted text and the second one is the key that used for encryption.'''
+def decryption(encrypt_text, key):
+    orig_text = []
+    for i in range(len(encrypt_text)):
+        '''In the decryption function encryption text
+        and key are subtracted, then added 26 modulo 26.'''
+        x = (ord(encrypt_text[i]) - ord(key[i]) + 26) % 26
+        x += ord('A')
+        orig_text.append(chr(x))
+    return ("".join(orig_text))
+
+
+if __name__ == "__main__":
+    string = input("Enter the message: ")
+    keyword = input("Enter the keyword: ")
+    key = generateKey(string, keyword)
+    encrypt_text = encryption(string, key)
+    print("Encrypted message:", encrypt_text)
+    print("Decrypted message:", decryption(encrypt_text, key))
+