True in some form, it always comes down again to the strength and
integrity of the original password.
Yes, even if a salt is unknown and it is a plain text, dictionary
password, then it doesn't take much for a brute force attempt at just
using the first two characters of each word and salting it with the word
to create the hash and seeing if it matches.
But just knowing the two character salt doesn't overly help in
decrypting the hash. Using a custom hash particularly using part of the
key itself as the hash increases the integrity and uniqueness of the
hash by an exponential factor. You have two values now that are
affecting the hash output value.
Something to chew on...
-J B
This begs the question of what would this method buy you over MD5?
Some people have "issue" with like passwords looking the same with MD5
encryption, also a one way hash.
But if you know the salt, then like passwords would also look the
same, right?
-B
Giff Hammar wrote:
For an example, look at how UNIX/Linux stores regular login passwords.
In
short, the salt is the first two characters in the password. When
comparing
passwords, you take the salt and the user supplied password, encrypt,
then
compare the two encrypted strings. If they match, the recently
supplied
password matches the original. AFAIK, that is the only way to verify
passwords encrypted with a one-way algorithm.
Giff
-----Original Message-----
From: chris smith [mailto:dmagick@xxxxxxxxx] Sent: Monday, April 17,
2006 4:36 PM
To: Sean Mumford
Cc: php-db@xxxxxxxxxxxxx
Subject: Re: MD5, MySQL, and salts
On 4/18/06, Sean Mumford <smumford@xxxxxxxxxxxxxxxxxx> wrote:
Hi Guys,
I'm working on securing user passwords in a MySQL 4 database with a
PHP5 frontend. I remember being told in one of my classes (I'm
currently a college junior) that the best way would be to hash a salt
and the password together and then store the hash in the database
instead of the plain MD5 hash. My question is, what is a good method
for the server and the database to agree on a salt value to use? I
know i could use a predefined variable, but I was wondering if
something dynamic might be better (timestamp, current date, something
like
that). Any ideas? Thanks in advance!
If it's a dynamic salt, how are you going to access it when you have
to
compare ?
There was an article either on phpsec.org or shiflett.org which talks
about
this.. can't find the link right now :(
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