We’ve talked about creating strong passwords in multiple groovy posts , but we’ve never given you a way to test them. There are several free internet tools that offer a localized password strength test and operate in any modern web browser. Most of these tools use common cryptography algorithms to determine the likelihood of a password cracker generating an exact match for an encrypted password’s translated MD5.
What is Password Entropy?
Entropy is the level of unpredictability that the password has, or in other words if a password has a higher level of entropy that means it has a higher chance of being something that will never be guessed.
To understand the basics of how long a password would take to crack vs. its amount of entropy, there is a very simplified formula to follow. Please note that this is very, very simplified and anyone in the cryptography field is likely shaking their head at this, but here it goes:
- 2^(the level of entropy) = number of guesses needed to crack
- Any average Joe can install password-cracker software and make about 1000 guesses per second.
- Divide # of guesses needed by guesses-per-second and you have the seconds of time required to crack the password, just divide according to days/hours/minutes.
- However, if we speed that up to crazy supercomputer levels (like this guy who built a 25-GPU machine that can do 350 billion guesses per second), it becomes a lot quicker. But, the guess rate is significantly slowed down depending upon which encryption algorithm is used. The typical website uses SHA1, which a supercomputer could crack at a rate of 63 billion guesses per second.
Keep in mind that while these passwords are stored on a web server, they are usually protected by a maximum number of password attempts over a certain amount of time. But, if the website ever gets hacked then its password hashes can be easily run through any offline cracking system that the hackers have set up.
Of the available tools, Rumkin’s strength test is my favorite. It’s just a simple box, and when you type in the password, it will tell you its strength, the character set, and its level of entropy.
- “tr0G0d4r” = 35.5 bits of entropy
35.5 bits of entropy = 398 days for the average Joe to crack, but only 0.5 seconds for a supercomputer to break. That translates to less than a minute for almost any cracking expert out there to break in!
- “mygmailpassword” = 58.9 bits of entropy
58.9 bits of entropy = 18,267,344 years for the average Joe password crack to break. Or on a supercomputer about 105 days, in theory.
- “i have a very strong password” = 107.4 bits of entropy
107.4 bits of entropy = 5,141,800,300,000,000,000 millennia for the average Joe password cracker to break. On a supercomputer, it would take 81,615,877,245 millennia to crack. It is highly unlikely it will ever be cracked unless your password is singled out and targeted by multiple systems.
Other sites that can test your password strength
Article Update 10/6/2017 (Published 4/9/13)