18 Jun
2009
18 Jun
'09
8:03 p.m.
On Thursday 18 June 2009, Dan Gahlinger wrote:
The strength of a password storage system has nothing to do with the
security of the passwords you are storing in it.
If you're storing passwords in plaintext in a world-readable file or
using a trivial crypt() function, it doesn't matter how secure your
passwords are.
If you're storing passwords securely (like a MD5 hash, with a reasonably
sized salt), then the strength of the password/passphrase matters.
brute-forcing a passphrase is not necessarily a
function of the
length especially where windows is concerned, or if another system,
where there are weaknesses in the cryptographic functions themselves.
If that's the case, I don't see how the randomness of a password matters
in your ability to crack it.
Re: passwords vs passphrases...
I don't see how you can claim that a password is more secure than a
passphrase. Using some basic combinatorics, you can calculate the
strength of each, based on the possible combinations.
A low estimate of the number of words in the English language is
500,000. If you use 4 words, and only 1/5 of the possible English
words makes grammatical sense in each position, that gives you
100,000^4 possible passwords, so 10^20 total possible passwords. Using
an eight charactor password, with any possible combination of generally
valid characters (we'll call that ASCII chars 32-127, to make the math
easier, or 96 possibilities), that gives you 96^8 possible passwords.
If we call that 100^8 to make the math easier, that's 10^16 passwords.
So, a conservative estimate for the number of possible passphrases vs an
overestimate of the number of possible passwords leaves passphrases
winning 10,000 to 1.
one portion of windows password stores saves the
password as an 8
character uppercase string, that's hardly very secure and can easily
provide clues as to the true password.
Really? I doubt this applies outside of home environments. I know that
the account/password distribution system we have at Purdue doesn't
distribute anything but a password hash, and pretty much nothing uses
LANMAN encrypted passwords anymore.
In any case, I doubt that most important passwords (by percentage of
passwords to systems) are (1) login passwords on Windows systems or (2)
handled by a Windows system outside of the client's web browser (if
even there).
and you just reinforced my suggestion, the methods
I've been using.
the password generators I've written produce not only hardened
passwords, and also passwords which are next to impossible to
remember, BUT are incredibly easy for the user to type in.
this does several things
it means the user never has to write them down,
they can never give out their password
however, the user has no issues logging in.
Huh? If they're "next to impossible to remember" then someone is more
likely to write them down than a short phrase that they can both
remember and type easily.
You seem to be
confusing a bad implementation of the translation of
plaintext to cryptotext and the poor storage of said cryptotext
with the relative security of passphrases vs. passwords. The two
are utterly distinct.
no, I'm not, and they are not necessarily distinct, dependent on the
system. any good security person has to take the system as a whole,
there are many "paths" to finding ways through the system, flaws in
implementation, weaknesses in cryptography, the human element, and of
course, others. This doesn't apply, at least in the case of
windows (and perhaps
others). On windows systems I've seen it decrypt the first (or
second) half of a password, or the first 8 characters, I've seen it
do portions in sections. all this with no access to cleartext.
So, which of these is it? And, where did you see it? What version of
the OS, in what program, etc? I can't check this, as I don't have
anything that runs Windows anymore to check this on.
I'd have to double-check if this has any
similarity for md5
passwords, I don't recall, though I doubt it.
You can't decrypt an MD5 hash. You can potentially find collisions, but
it's still not a trivial proposition, and you definately can't do it in
parts.
Also, it still doesn't necessarily give you the actual password, or
something with characters in a set that you can enter into the password
entry field.
windows is a good example because it is (still) the
most used OS in
the world, and a large percentage of people have a false sense of
security in using it. The above includes Vista.
I don't think that the security of the password that people use to log
into the home system (if they even have a password set for that) is a
valid measure of security of anything except for what's stored on their
home PC.
Pat
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