@@ -0,0 +1,62 @@
+import sys, random
+
+LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+
+def main():
+message = input('Enter message: ')
+key = 'LFWOAYUISVKMNXPBDCRJTQEGHZ'
+resp = input('Encrypt/Decrypt [e/d]: ')
+
+checkValidKey(key)
+
+if resp.lower().startswith('e'):
+mode = 'encrypt'
+translated = encryptMessage(key, message)
+elif resp.lower().startswith('d'):
+mode = 'decrypt'
+translated = decryptMessage(key, message)
+
+print('\n%sion: \n%s' % (mode.title(), translated))
+
+def checkValidKey(key):
+keyList = list(key)
+lettersList = list(LETTERS)
+keyList.sort()
+lettersList.sort()
+
+if keyList != lettersList:
+sys.exit('Error in the key or symbol set.')
+
+def encryptMessage(key, message):
+return translateMessage(key, message, 'encrypt')
+
+def decryptMessage(key, message):
+return translateMessage(key, message, 'decrypt')
+
+def translateMessage(key, message, mode):
+translated = ''
+charsA = LETTERS
+charsB = key
+
+if mode == 'decrypt':
+charsA, charsB = charsB, charsA
+
+for symbol in message:
+if symbol.upper() in charsA:
+symIndex = charsA.find(symbol.upper())
+if symbol.isupper():
+translated += charsB[symIndex].upper()
+else:
+translated += charsB[symIndex].lower()
+else:
+translated += symbol
+
+return translated
+
+def getRandomKey():
+key = list(LETTERS)
+random.shuffle(key)
+return ''.join(key)
+
+if __name__ == '__main__':
+main()