# Strengthen Your Cipher with Substitution

At the end of the Cybersecurity: Encryption Intro tutorial, there’s a Your Turn in the Substitution Ciphers page where you created a scrambled_alphabet_cipher script.  This kind of function is a much better defense against brute force attacks.  Instead of testing 93 possible shifts, a brute force attack would have to try decrypting with 26! permutations of the alphabet.  The term 26! is pronounced 26 factorial.

3! = 3 * 2 * 1 = 6
4! = 4 * 3 * 2 * 1 = 24
5! = 5 * 4 * 3 * 2 * 1 = 120

26! = 403,291,461,126,605,635,584,000,000

Wow!  That would be a lot of rearrangements of the alphabet for a brute force algorithm to crack.  Also, who would try to look at all those combinations to find the intelligible text?

### Example script: scrambled_alphabet_cipher

• Enter, save, and flash scrambled_alphabet_cipher into a micro:bit.
```# scrambled_alphabet_cipher

from microbit import *

# Scrambled alphabet cipher.
def scramble(text, encrypt):
alpha  = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
result = ""

if encrypt is False:
temp = alpha
alpha = crypta
crypta = temp

for letter in text:
letter = letter.upper()
index = alpha.find(letter)
result = result + crypta[index]

return result

# The script starts executing statements from here.

sleep(1000)

print("Set your keyboard to CAPS LOCK.")
print()

while True:
text = input("Enter a CAPS LOCK string: ")

result = scramble(text, True)

print("scrambled result =", result)

result =  scramble(result, False)

print("unscrambled result =", result)```

• Click the Open Serial button.
• Type HAPPY into the terminal.
• Verify that the scrambled result is RPBBL.  That’s the encrypted result.
• Verify that the unscrambled, decrypted result is HAPPY.