Python Generate Secure Password

Requirements

How to come up with a randomly generated password or key is a common problem or challenge when programming, or just in security. On top of just randomly generating a password, there are some custom criteria pieces that are also challenges:

• Password Length
• Certain number of uppercase letters
• Certain number of lowercase letters
• Certain number of numbers
• Certain number of special characters
• Finally, a restriction to only a fixed set of special characters. Some special characters can be very unfriendly to different operation systems or platforms.
  • For example, on Cisco IOS or NXOS, you cannot easily use a question mark as it will signal the OS to display the current help.

Required Modules

All of the modules used in this code, are included with Python 2.7.5+.

• random
• string

What the Code Does

By default the code will:

• Generate a password length of 25 Characters
• 35% of that password length will be lowercase
• 35% of that password length will be uppercase
• 25% of the password length will be numbers
• to make the password the full length of 25 characters, it will add the special characters !@#$ randomly until the length is 25
• the code will then randomly shuffle the 25 characters

  • random.shuffle(pWcharList)
                    

Example of the run

>> python gen.py 
pIB4L#!E0muq8Wpx4XI#l4R6v

The Code

import random
import string

def generatePw():
    pWcharList = []
    special = '!@#$'
    pWlen = 25
    # 35 percent will be lowercase
    for x in range(int(pWlen * .35)):
        pWcharList.append(random.choice(string.ascii_lowercase))
    # 35 percent will be uppercase
    for x in range(int(pWlen * .35)):
        pWcharList.append(random.choice(string.ascii_uppercase))
    # 25 percent will be numbers
    for x in range(int(pWlen * .25)):
        pWcharList.append(random.choice(string.digits))
    # Add the remaining length of the string with special characters
    for x in range(pWlen - len(pWcharList)):
        pWcharList.append(random.choice(special))

    random.shuffle(pWcharList)
    newPw = ''.join(pWcharList)
    return newPw

if __name__ == '__main__':
    print(generatePw())