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Date:      Sat, 29 Dec 2001 23:00:12 -0600 (CST)
From:      Ryan Thompson <ryan@sasknow.com>
To:        Rik <freebsd-security@rikrose.net>
Cc:        <freebsd-security@FreeBSD.ORG>
Subject:   Re: MD5 password salt calculation
Message-ID:  <20011229224936.E46948-100000@catalyst.sasknow.net>
In-Reply-To: <20011230043020.A9927@spoon.pkl.net>

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Rik wrote to Ryan Thompson:



Hi Rik,


> Salt is just some randomness thrown in so that you can't just make
> a standard dictionary to compare hashed passwords with. All you
> need to do is make the relevant number of random chars.

Right.. I gather it's still the convention to use $1$ to differentiate
between DES/MD5, in the case where both password formats are being
imported. Is $1$ pretty much caught on everywhere? I've seen it in
OpenBSD and NetBSD, probably even Linux, but it's been awhile since I
looked.


> Personally, I just run the current time as a string (from
> strftime(3)) through the hash, and take the first couple of chars
> as an index into an array of allowable chars (modulo the size of
> the array, obviously).
>
> I'm sure someone on this list will tell us if that's a completely
> stupid way of generating salt...

:-) Well, it doesn't sound too unreasonable...(though using integer
time would be faster by a mult. constant if your process is CPU bound)
the approaches that I've seen use some kind of random data (like
current sec+usec) passed through a char array... so I suppose that's
essentially the same thing.

- Ryan

-- 
  Ryan Thompson <ryan@sasknow.com>
  Network Administrator, Accounts

  SaskNow Technologies - http://www.sasknow.com
  #106-380 3120 8th St E - Saskatoon, SK - S7H 0W2

        Tel: 306-664-3600   Fax: 306-664-1161   Saskatoon
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