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Password Security: Why the Horse Battery Staple Is Not Correct
First time accepted submitter Dadoo writes By now, everyone who reads Slashdot regularly has seen the XKCD comic discussing how to choose a more secure password, but at least one security researcher rejects that theory, asserting that password managers are the most important technology people can use to keep their accounts safe. He says, "In this post, I'm going to make the following arguments: 1) Choosing a password should be something you do very infrequently. 2) Our focus should be on protecting passwords against informed statistical attacks and not brute-force attacks. 3) When you do have to choose a password, one of the most important selection criteria should be how many other people have also chosen that same password. 4) One of the most impactful things that we can do as a security community is to change password strength meters and disallow the use of common passwords."
Just because the author asserts that the password system is broken doesn't make Randall Munroe's point about passwords incorrect. "At least one security researcher rejects that theory." What theory does he reject? It's simple math that shows that Munroe's method is better for creating stronger passwords (at least for the average user), but that has nothing to do with relying on password managers...
Good, bad & ugly - Your password
PASSWORD REQUIREMENTS
A good password must have two properties:
1) It has been memorized by the user
2) It is difficult to guess for a third person (even if he/she knows the user well)
But in most cases another requirement is thrown into the mix:
3) The password shell be complex (have a high entropy)
Usually the requirements take the form of a password policy like this:
The password must be at least 8 characters long
The password must contain upper- and lower-case letters
The password must contain a number
The password must contain a non-alphanumeric character
You notice anything? Yep, this policy only focuses on the third requirement. And it does so at the expense of the first requirement and (knowing human psychology) it also has a negative impact on the second requirement.
THREATS TO PASSWORDS
Let us take look at how the security of password can be compromised:
- The input of the password has been observed (by eavesdropping, key-loggers or by the ordinary Mark 1 Eyeball)
- The password has been re-used by the user in a different context where the attacker has access to it
- The attacker gained access to the encrypted storage of password and managed to extract it from there
- The password has been guessed by the attacker
How does having a complex password help you against these attacks?
In case of an attacker observing the user entering the password, no complexity will help. Rather the contrary, a password with mixed upper/lower-case, numbers and special characters is entered at a significantly slower pace. This helps an attacker observing the password by good old-fashioned peeking.
If the password is known to the attacker from the use in a different context, the complexity is no help either. Knowing the psychological side, cryptic passwords are rather compound the problem. Once a user has found a password that fits the typical policy, he tends to use it wherever such a password policy is in place and therefor increases the chances of an attacker to use a known password of the user in a different context.
In case of access to the encrypted password store, the complexity clearly helps to hamper the attacker (if the password is encrypted properly).
One would expect that password policy should help making a password un-guessable for a third person. From my personal observation the contrary is true. Under the watchful eye of a password policy they tend to stick to first names, upper-casing the first or last letter, replacing characters by similar looking special characters or numbers and/or adding numbers at the end (like birthdays).
Summary: Only in one attack scenario choosing a complex password helps, in all other scenarios it does not have any or even a negative impact. So let us look at this scenario a bit more detailed.
DECRYPTING PASSWORDS
To decrypt the password of a user, the attacker has first to have access to the password storage. At which point the first and most critical security failure has already occurred. And the user had nothing to do with it.
When it comes to decrypting a password, the algorithm used is a more important than the complexity of the password. If the service provider has not done his home work, complex passwords offer only little protection. This is another critical point, where the user has no influence whatsoever.
But in case of the service provider having botched the safety of his password file but made everything correct when choosing the algorithm the complexity of the user passwords can offer extra protection against the attacker.
Does this case justify all the negative impact?
I want to point out, that the safety of the encrypted password is not the responsibility of the user. So would say: Don't make him part of the process here. Don't shift the responsibility to to him where the service provider is responsible.
Remark: I did not specifically address the issue of an attacker
Not having the manager available is a big problem. I redid all my passwords after the Heartbleed issue, and pretty much maxed out the password for each of my important accounts. Was great on my PCs where I had KeePassX, but the first time I had to enter a 24-character randomly generated password with special characters on my cellphone to log in, I realized why it will never work for the average person. Big, long complex passwords are great until you have to type them in on a tiny ass keyboard.
IT companies like Microsoft? You've just described the exact password policy that the largest software company in the world uses to enforce a "strong password", under the guises of best practices. I don't know why you blame the end user, when the manufacturer is the one perpetuating this system through documentation, training certifications, and the operating system itself.
But all that aside, those passwords are plenty good enough. Any system that allows an attacker to brute force passwords, especially online, has a design problem. It would take an idiot to build a system that allows 1000 password guesses per second without a timeout. Guess wrong 5 times, and you get locked out for 10 minutes, and a warning email sent. Suddenly you've increased the brute force time to thousands of years, and the target is aware. This is basic stuff, and just about any dictionary word is safe.
Ever increasing complexity is an unnecessary solution. Password breaches are not being done through brute force, there's no real reason to make brute force harder.
Not only that, but remember multiple different passwords like that, because some websites/databases don't allow the carat symbol.
I have over 20 different passwords for different sites at work. Some of them don't allow a password under 12 characters, some don't allow a password over 8 characters. Some don't allow a number or symbol in the first space. Some only allow 6 different symbols to be used. Some don't allow capital letters. Some require capital letters.
It's insane. It's not possible for my coworkers to remember them all, so they get written down, which certainly doesn't increase security. Many times people keep their passwords in their phones. Some write them down on paper and keep them in their wallet. Some folks leave them on notes in their cubicle.
Then, to top it off, some require the password to change every 30 days. Some every 60 days. Some every 90 days.
These insane attempts to force password security have actually destroyed it.