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Date:      Sat, 16 Aug 2003 10:22:49 -0700
From:      underway@comcast.net (Gary W. Swearingen)
To:        Terry Lambert <tlambert2@mindspring.com>
Cc:        Glenn Johnson <gjohnson@srrc.ars.usda.gov>
Subject:   Re: password strength checking not consistently implemented
Message-ID:  <5d7k5dcyae.k5d@mail.comcast.net>
In-Reply-To: <3F3DD290.D237F6D2@mindspring.com> (Terry Lambert's message of "Fri, 15 Aug 2003 23:43:28 -0700")
References:  <20030814225453.GA1385@node1.cluster.srrc.usda.gov> <3F3C9E22.D24F3C0A@mindspring.com> <9ek79edgvu.79e@mail.comcast.net> <3F3DD290.D237F6D2@mindspring.com>

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Terry Lambert <tlambert2@mindspring.com> writes:

> You're assuming that everyone uses dictionary attacks, which is
> really not true these days.

No, I was assuming that crackers COULD use dictionary attacks.  I
won't quote it again, but you clearly implied that it takes "a lot
longer" to crack passwords in the absence of strength checking.  Maybe
that's true if YOU assume that crackers can't use dictionaries (though
I still doubt if it takes "a lot" longer).  But they can and would use
dictionaries in the absense of strength checking and it would not take
a lot longer to crack passwords.  It would take less time, on average.

This whole discussion breaks down eventually, because if crackers are
taking account of strength checking, then they are using a form of
dictionary attack.  They are searching the keyspace starting with
the most likely passwords, however crudely this is done.

But maybe you meant to say that brute force methods are so good that
they will always use brute force instead of dictionaries, whether or
not the latter are sometimes faster.  So we might as well allow all of
the passwords to be "password", as long as our lack of strength
checking "forces" crackers to search the whole keyspace so they wind
up cracking fewer of them.  That makes SOME sense, but people
shouldn't be expected to be altruistic enough take on the risk that
all those "password" passwords won't be exploited, maybe manually.

> Actually, thanks to strength-checkers, most crackers have switched
> to brute-force, since dictionary attacks no longer work.  For some
> definitions of "strength checking", they can also ignore the search
> space where passwords contain all alphabetic characters.

So convince me.  What did you mean by "a lot longer"?  For one
password, are we talking a millisecond or a week or what?  It it long
enough for me to care how much longer it takes?  Is it worth the risk
of allowing passwords like "password"?


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