This morning I got an email from someone about secure passwords. The email was a link to this article. Before even opening the link I had a good idea of what it was going to say…make your passwords use all four character sets and make them random, but base it on a phrase that you can easily remember. My guess (and I was correct) was that it was going to ignore/gloss over the issue of password length.
In years past I was a strong proponent of passwords that used all four character sets (UPPERCASE, lowercase, 12345, !@#$%^%). I’m really not anymore. Reason being that password length has a much greater effect on whether a password can be cracked than does complexity. One of the best articles I have seen on this issue was an InfoWorld article back in 2006. The author did a great job of mathematically showing how the two factors in password complexity (length and number of possible characters) work together.
In the times that I have done password audits for the ministry I work for, this has proven out every time. I have seen some very complex passwords that were shorter in length get cracked. I have never cracked a long password. That is the primary reason that my non-admin password is currently 20+ characters long. The password for my admin account? Somewhere north of 30 characters. Good luck cracking it while I am still alive.
A few paragraphs from the InfoWorld article above that I most enjoyed…:
For everyone using six- to nine-character passwords with “complexity,” I appreciate it. I get paid to break in to systems for a living, and you make my job easier.
Strength is provided by increasing the number of possible passwords the attacker has to guess (let’s call this the keyspace even though it really isn’t appropriate in this context). The keyspace is represented mathematically as X^L, where X is the number of possible characters that can be in the password and L is the length. If you do the basic analysis, you can see that changes in L are more significant, character for character, than changes in X.
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And because most users also use dictionary words as the root to their “complex” password, and follow other common conventions (capitalized letters are at the beginning, numbers are at the end), a simple hybrid attack will break most of them in less than a day. Trust me, I know — I do it for a living.
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So, when trying to increase the strength of your passwords, my advice is to consider length as much or more than you consider complexity. For my money, length is all the protection I need. Make your admin and root passwords 15 or more characters long and forget about complexity — at 15 characters-plus, they are all but uncrackable.
