Шифр сдвига

#Реализация шифрования / дешифрование простейшим шифром сдвига
#Взлом шифра статистическим криптоанализом(только на русском)

#!/usr/bin/python3

import collections

def enCrypt(filename,key=3):
    encrypte = ""
    f = open(filename)
    for char in f.read():
        encrypte+=chr(ord(char) + key)
    return encrypte

def deCrypt(encrypted,key =3):
    decrypted = ""
    for char in encrypted:
        decrypted+=chr(ord(char)- key)
    return decrypted

def mostFrequent (encrypted) :
    charCount = {}
    for char in encrypted:
        if char != '#':
            if char not in charCount:
                charCount[char] = 1
            else:
                charCount[char] += 1
    char_counter = collections.Counter(charCount).most_common(4)
    return  char_counter

def tryGetKeys(mostReq):
    keys =  []
    for char in mostReq:
        if ord(char[0]) > 0 : keys.append(ord(char[0]) - ord('о'))
    return keys

encrypted = enCrypt("input")
decrypted = deCrypt(encrypted)
most_Frequent = mostFrequent(encrypted)
keys = tryGetKeys(most_Frequent)
for key in keys:
    print(deCrypt(encrypted,key))