In this chapter, we will focus on testing substitution cipher using various methods, which helps to generate random strings as given below −

import random, string, substitution
def main():
   for i in range(1000):
      key = substitution.getRandomKey()
      message = random_string()
      print(''Test %s: String: "%s.."'' % (i + 1, message[:50]))
      print("Key: " + key)
      encrypted = substitution.translateMessage(message, key, ''E'')
      decrypted = substitution.translateMessage(encrypted, key, ''D'')
      
      if decrypted != message:
         print(''ERROR: Decrypted: "%s" Key: %s'' % (decrypted, key))
         sys.exit()
      print(''Substutition test passed!'')

def random_string(size = 5000, chars = string.ascii_letters + string.digits):
   return ''''.join(random.choice(chars) for _ in range(size))
if __name__ == ''__main__'':
   main()

Output

You can observe the output as randomly generated strings which helps in generating random plain text messages, as shown below −

After the test is successfully completed, we can observe the output message Substitution test passed!.

Thus, you can hack a substitution cipher in the systematic manner.