Initial

ciphers/vigenere_cipher.py

@@ -0,0 +1,60 @@
+LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+
+def main():
+    message = input('Enter message: ')
+    key = input('Enter key [alphanumeric]: ')
+    mode = input('Encrypt/Decrypt [e/d]: ')
+
+    if mode.lower().startswith('e'):
+        mode = 'encrypt'
+        translated = encryptMessage(key, message)
+    elif mode.lower().startswith('d'):
+        mode = 'decrypt'
+        translated = decryptMessage(key, message)
+
+    print('\n%sed message:' % mode.title())
+    print(translated)
+
+def encryptMessage(key, message):
+    '''
+    >>> encryptMessage('HDarji', 'This is Harshil Darji from Dharmaj.')
+    'Akij ra Odrjqqs Gaisq muod Mphumrs.'
+    '''
+    return translateMessage(key, message, 'encrypt')
+
+def decryptMessage(key, message):
+    '''
+    >>> decryptMessage('HDarji', 'Akij ra Odrjqqs Gaisq muod Mphumrs.')
+    'This is Harshil Darji from Dharmaj.'
+    '''
+    return translateMessage(key, message, 'decrypt')
+
+def translateMessage(key, message, mode):
+    translated = []
+    keyIndex = 0
+    key = key.upper()
+
+    for symbol in message:
+        num = LETTERS.find(symbol.upper())
+        if num != -1:
+            if mode == 'encrypt':
+                num += LETTERS.find(key[keyIndex])
+            elif mode == 'decrypt':
+                num -= LETTERS.find(key[keyIndex])
+
+            num %= len(LETTERS)
+
+            if symbol.isupper():
+                translated.append(LETTERS[num])
+            elif symbol.islower():
+                translated.append(LETTERS[num].lower())
+
+            keyIndex += 1
+            if keyIndex == len(key):
+                keyIndex = 0
+        else:
+            translated.append(symbol)
+    return ''.join(translated)
+
+if __name__ == '__main__':
+    main()