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I recently posted a program that I wrote that would change a password after being validated, the program can be found here.

I have rewritten this program, it has a couple new features:

• Usernames
• Decryption
• Program related errors

How it works. At the beginning of the program you asked to make a username, that username is stored in a file, you are then asked to create a password, the password is run through a series of verification such as length, characters, integers, etc.. If the password completes verification that password is encrypted (using a simple encryption technique) and stored into a file. From there the password will be asked for to login. If you fail to put in the correct password to many times, both the user name and the password file are truncated back to 0.

Source:

# -*- encoding: UTF-8 -*-
import re
import getpass
class ValidatorError(Exception):
 pass
class SecondAuthenticationError(Exception):
 pass
class PasswordValidator(object):
 """ A password validator, used to validate a password for
 specific characters, numbers, and special characters """
 def __init__(self, password):
 self.password = password
 self.validators = [self.validate_integers(self.password), self.validate_spec_chars(self.password),
 self.validate_length(self.password), self.validate_lower_case(self.password),
 self.validate_upper_case(self.password)]
 def validate_length(self, password): # Check the length, gotta be over 8
 if len(password) > 8:
 return True
 else:
 raise ValidatorError("Failed to validate length. Allowed length: (> 8)")
 def validate_upper_case(self, password): # Check for upper case characters
 if re.search("[A-Z]", password) is not None:
 return True
 else:
 raise ValidatorError("Failed to validate upper case characters. (A - Z)")
 def validate_lower_case(self, password): # Check for lower case characters
 if re.search("[a-z]", password) is not None:
 return True
 else:
 raise ValidatorError("Failed to validate lower case characters. (a - z)")
 def validate_integers(self, password): # Check for integers
 if re.search("[0-9]", password) is not None:
 return True
 else:
 raise ValidatorError("Failed to validate integers. (0 - 9)")
 def validate_spec_chars(self, password): # Check for special characters
 if re.search("[!$&*]", password) is not None:
 return True
 else:
 raise ValidatorError("Failed to validate special characters. Allowed: ( !$&* )")
 def validate(self):
 """ Validate everything. """
 try:
 return all(validators for validators in self.validators)
 except ValidatorError as e:
 print e
 return False
def encrypt(password):
 """ Encrypt the password simply example: bíFuo <- says Test!23456
 :type password: String """
 encrypt_arr = list(password)
 new_encrypt_arr = []
 for i in encrypt_arr:
 num = ord(i) + 3
 new_encrypt_arr.append(chr(num))
 return ''.join(new_encrypt_arr)
def decrypt(encrypted_password):
 """ Decrypt a password when needed
 :type encrypted_password: String (UTF-8) """
 decrypt_arr = list(encrypted_password)
 new_decrypt_arr = []
 for char in decrypt_arr:
 num = ord(char) - 3
 new_decrypt_arr.append(chr(num))
 return ''.join(new_decrypt_arr)
def obtain_password():
 """ Get the password, simple and easy with getpass library """
 return getpass.getpass('Change your password: ')
def second_authentication(password_to_verify):
 """ Verify that the password is what the user wants it to be,
 by asking for it a second time.
 :type password_to_verify: String """
 password = getpass.getpass('Enter password a second time: ')
 if encrypt(password) == encrypt(password_to_verify):
 with open('passwords.txt', 'a+') as f:
 f.write(encrypt(password_to_verify))
 return "Password changed successfully."
 else:
 raise SecondAuthenticationError("Passwords encryption did not match.")
def erase_all(file_list):
 """ Erase all data from the file because you where an idiot and
 forgot your password
 :type file_list: List """
 for files in file_list:
 open(files, 'w').close()
def user_login():
 """ Login and create a username, maybe """
 with open('username.txt', 'a+') as f:
 if f.readline() is "":
 username = raw_input("First login, enter a username to use: ")
 f.seek(0)
 f.write(username)
 else:
 login_id = raw_input("Enter username: ")
 f.seek(0)
 if login_id == f.readline():
 return True
 else:
 print "Invalid username."
 return False
def user_password():
 """ If you mess up all the data will be gone. """
 files = ['username.txt', 'passwords.txt']
 attempts = 3
 while True:
 password_to_compare = getpass.getpass("Enter password: ")
 with open('passwords.txt', 'a+') as password:
 if password.readline() is not "":
 password.seek(0)
 if password_to_compare == decrypt(password.readline()):
 return True
 else:
 print "Invalid password.."
 if attempts == 0:
 print "Exiting and erasing data.."
 erase_all(files)
 print "All data truncated."
 break
 else:
 attempts -= 1
 print "You have {} attempts left..".format(attempts)
if __name__ == '__main__':
 try:
 if user_login() is True:
 if user_password() is True:
 print "Welcome home.."
 else:
 password_to_verify = obtain_password()
 val = PasswordValidator(password_to_verify)
 if val.validate() is not False:
 print second_authentication(password_to_verify)
 except ValidatorError, SecondAuthenticationError:
 print "Failed to verify, password and username truncated"
 erase_all(['username.txt', 'password.txt'])