Will Passphrases Foretell the Death of Pa55.W0rd5?

By Larry Seltzer  |  Posted 2004-10-25 Print this article Print

Opinion: Microsoft blogger starts controversy over the proper password techniques, but the answer isn't so obvious.

How long and complex should a password be? At what point is it effectively uncrackable? Time out: Look at that opening paragraph. Its 87 characters long, but it could be your password to your Windows system. Yes, even with the spaces in it. Technically, this has become known as a "passphrase."

Robert Hensing, a member of Microsofts Security Incident Response Team, has written in his blog that you shouldnt use passwords anymore for Windows systems—you should use passphrases. The blog entry has generated a lot of interest on security lists. Many agree with Hensing, and theres a lot I like about the idea. The discussions also raised my awareness of cracking tools for Windows passwords that do things you might not believe possible.

My opening lines might not make a good passphrase because its not very memorable. But lets say youre a Dead Head: "Its just a box of rain, I dont know who put it there" is a very strong passphrase, and it might be easy to remember. It has upper and lower case, punctuation and 58 characters. The downside relative to a more conventional password is that it has upper and lower case, punctuation and 58 characters. Its going to take a while to type, and youre more likely to make mistakes on it.

As Hensing points out, Windows has supported passphrases of up to 127 characters since Windows 2000. But boilerplate password advice from people like me has always focused on bizarre words that we kid ourselves as being easy to remember, like "Ih8m0d3rnART!" ("I hate modern art"). Take a phrase you can remember and distort it into a password. Hensing asks why not just use the phrase?

In fact, the "Ih8m0d3rnART!" example is instructive in another way. While it looks long and complex, and is relatively impervious to certain types of attacks, its only 13 characters and is therefore vulnerable to a weakness in Windows 2000 password hash methodology. Ill get into it more in a future column, but if you have local administrator access to the system, its possible to reverse-engineer Windows passwords up to a particular length. As I understand it, this problem has been eliminated in Windows 2003 domains, but remains in Windows 2000 for reasons of backward compatibility with third-party programs.

Next page: Malwares embedded dictionaries.

Larry Seltzer has been writing software for and English about computers ever since—,much to his own amazement—,he graduated from the University of Pennsylvania in 1983.

He was one of the authors of NPL and NPL-R, fourth-generation languages for microcomputers by the now-defunct DeskTop Software Corporation. (Larry is sad to find absolutely no hits on any of these +products on Google.) His work at Desktop Software included programming the UCSD p-System, a virtual machine-based operating system with portable binaries that pre-dated Java by more than 10 years.

For several years, he wrote corporate software for Mathematica Policy Research (they're still in business!) and Chase Econometrics (not so lucky) before being forcibly thrown into the consulting market. He bummed around the Philadelphia consulting and contract-programming scenes for a year or two before taking a job at NSTL (National Software Testing Labs) developing product tests and managing contract testing for the computer industry, governments and publication.

In 1991 Larry moved to Massachusetts to become Technical Director of PC Week Labs (now eWeek Labs). He moved within Ziff Davis to New York in 1994 to run testing at Windows Sources. In 1995, he became Technical Director for Internet product testing at PC Magazine and stayed there till 1998.

Since then, he has been writing for numerous other publications, including Fortune Small Business, Windows 2000 Magazine (now Windows and .NET Magazine), ZDNet and Sam Whitmore's Media Survey.

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