Re: Salt in encrypted password in pg_shadow

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: David Garamond <lists(at)zara(dot)6(dot)isreserved(dot)com>
Cc: Richard Huxton <dev(at)archonet(dot)com>, pgsql-general(at)postgresql(dot)org
Subject: Re: Salt in encrypted password in pg_shadow
Date: 2004-09-07 19:09:28
Message-ID: 2897.1094584168@sss.pgh.pa.us
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David Garamond <lists(at)zara(dot)6(dot)isreserved(dot)com> writes:
> Tom Lane wrote:
>> Also, MD5 hashing is fast enough that I'm not sure the above is really
>> significantly cheaper than a straight brute-force attack, ie, you just
>> take your list of possible passwords and compute the hashes on the fly.
>> The hashes are going to be much longer than the average real-world
>> password, so reading in a list of hashes is going to take several times
>> as much I/O as reading the passwords --- seems to me that it'd be
>> cheaper just to re-hash each password.

> Many people use short and easy-to-guess passwords (remember we're not
> talking about the superuser only here), so the dictionary attack can be
> more effective than people think.

And that responds to the speed argument how? I quite agree that a
guessable password is risky, but putting in a random salt offers no
real advantage if the salt has to be stored in the same place as the
encrypted password.

regards, tom lane

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