But when you say cracking, you'd have to have the password hashes to crack. And if they are salted hashes then you are FUBAR, there are no rainbow tables for that.

Now, if you're talking brute force attacks, its a different story. And that's why a lockout policy is important.

Finally, a 20 character minimum for a passphrase is ridiculous. If you just consider 52 chars (upper/lower, no spaces or punctuation) a 15 character passphrase has 5.5 X 10^25 values. Your aforementioned password poliicy (8 chars, at least 1 numeric) has a minimum complexity of 52^7*10 or 1.0 X 10^13, significantly lower than the 15 character passphrase. So... what kind of complexity are you really looking to enforce?

-dhs


Dean H. Saxe, CISSP, CEH
[email protected]
"I have always strenuously supported the right of every man to his own opinion, however different that opinion might be to mine. He who denies another this right makes a slave of himself to his present opinion, because he precludes himself the right of changing it."
    -- Thomas Paine, 1783


On Mar 9, 2009, at 12:08 PM, Shane wrote:

I agree that users do choose poor passwords. But even using an extended character set you see them choose passwords like "T!mmy". From a cracker's
point of view there is little difference between Timmy and T!mmy.

I definitely agree that long pass phrases are best all around - even using words. Set the min length at 20 and let the user choose whatever they want.

I just brought up the point because I have seen more than one website,
including my bank, that forces an extended char set but limits the password
length to a MAX of 8 characters.  Yeesh.

Security in layers - everything is a compromise.

Shane Heasley
www.CTek-Media.com

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Dean H. Saxe
Sent: Monday, March 09, 2009 10:54 AM
To: [email protected]
Subject: Re: [ACFUG Discuss] Password CFinput regular expression - throws
alert/error after correction also

I'm not sure I totally agree with you.

Yes, the math is not good when you force character sets like this, but the
reality is that users choose bad passwords.
http://www.schneier.com/essay-144.html
The enforcement of complex passwords improves overall complexity for most
users.

From the social engineering side, you are right, users may write down their passwords. But you'd have to find the password to break in, as opposed to guessing the password from a large, complex pool. So its a balancing act.

My suggestion is the use of passphrases such as "yellow polkadot pancakes". You trade length for complexity but increase the ability of memorization.
If you then add in some kind of special characters or "leet speak" the
passwords are extremely difficult to guess or break.

Finally, all of this is useless if you allow the passwords to be recovered or you don't enforce server-side lockouts to slow/stop brute force attacks
against passwords.  There's a lot more to do than just enforce good
passwords if you want to have a secure authentication system.

-dhs


Dean H. Saxe, CISSP, CEH
[email protected]
"What is objectionable, what is dangerous about extremists is not that they
are extreme, but that they are intolerant."
    -- Robert F. Kennedy, 1964


On Mar 9, 2009, at 11:46 AM, Shane wrote:

This is off topic - but I thought I would throw it in for free:

Forcing an extended character set (upper case, numbers, special
characters) on the user frequently does not lead to good security.

First, from the mathematical side, the length of the password has much more bearing on how difficult it is to crack than the added complexity gained from using an extended character set. So sliggyfiverbotgar is
much harder to crack than ^%tgYh.  As a practical matter, passwords
longer than 10 characters are not
generally breakable - even when composed of mostly English words.
Each extra character adds so many permutations that you need to be the
NSA to brute force longer passwords.

On the social engineering side.  If you force average users to use
an extended character set they have a hard time remembering them.
If they can't easily remember them they write them down and all too
frequently post them next to their monitor.  It's all a balancing act
- and it varies by situation.  I usually go for what you have -
minimum of 8 characters, with at least one number.  Sometimes I
require mixed case also.  I don't force special characters as that
tends to make too many users write down their passwords.
From: [email protected] [mailto:[email protected]] On Behalf Of Ajas
Mohammed
Sent: Monday, March 09, 2009 10:28 AM
To: [email protected]
Subject: [ACFUG Discuss] Password CFinput regular expression - throws
alert/error after correction also

Hi there,

I have this code which checks if password is strong i.e. atleast 8
characters long, consiting of one Upper case and one Lower case and
one Number.and if not alerts the user about it. I am using a regular
expression to do this as u can see from code below. The problem is
that once the alert is displayed, even if the user corrects the error
and enters a strong password, the error alert does not go away. For
example, if i entered password for the first time, then obviously I
will get alert saying password is not strong. Then, afterwards if i
correct password to be lets say Leave1234 which is 9 chars, has one
uppper case, one lower case and has a number also, I still end up
getting password not strong message. I tried removing onBlur,OnSubmit
one at a time but doesnt work.

Any ideas????

Here is the code

New Password:
    <!--- some possible regular expressions i used new_password --->
     <!--- ^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,}$ or  --->
    <cfinput type="password" name="new_password"
validate="regular_expression" pattern="^(?=.*\d)(?=.*[a-z])(?=.*[A-
Z]).{8,}$" validateat="onBlur,onSubmit,onServer" message="Your
password is not strong. Your password should be atleast 8 characters
long, consiting of one Upper case and one Lower case and one Number."


<Ajas Mohammed />
http://ajashadi.blogspot.com
We cannot become what we need to be, remaining what we are.
No matter what, find a way. Because thats what winners do.
You can't improve what you don't measure.
Quality is never an accident; it is always the result of high
intention, sincere effort, intelligent direction and skillful
execution; it represents the wise choice of many alternatives.
No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 8.0.237 / Virus Database: 270.11.9/1990 - Release Date:
03/08/09 17:17:00


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Version: 8.0.237 / Virus Database: 270.11.9/1990 - Release Date: 03/08/09
17:17:00



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