[pLog-svn] Salted MD5

Matt Wood matt at woodzy.com
Tue Mar 11 16:36:48 EDT 2008 

At the login page you could do a check on the length of the database field
returned (md5 is shorter than sha256), and since you have the cleartext
password at that point you can recompute the new hash after comparing it to
the md5($cleartext) to see if it matched.

On Tue, Mar 11, 2008 at 2:04 AM, Mark Wu <markplace at gmail.com> wrote:

>  ** sha2($salt + sha2($password + $salt))
>
> I consider this before, the problem is I have to keep the compatibility.
>
> In lieftype 1.2.x and before, the $password is stored in database with
> md5($password)...
>
> So, any algorithm have to based on this, like
>
> sha2($salt + md5($password) + sha2($salt))  or
>
> sha2(md5($password) + $private_key)
>
> Or, there is no way for us to upgrade.... since we can not get the
> original plain text password
>
> Unless we leave an option for user( administrator) to use the old
> algorithm.
>
> Mark
>
>  ------------------------------
>  *From:* plog-svn-bounces at devel.lifetype.net [mailto:
> plog-svn-bounces at devel.lifetype.net] *On Behalf Of *Matt Wood
> *Sent:* Tuesday, March 11, 2008 1:49 PM
>
> *To:* LifeType Developer List
> *Subject:* Re: [pLog-svn] Salted MD5
>
>   From a cryptographic standpoint, since sha256 has a larger byte output,
> there are situations where the md5 calculation will actually reduce the
> number of bytes of "randomness" (entropy). And since we're talking about a
> WebApp here... not a high speed wireless encryption scheme, why not just use
> sha256 all the way through? Same for the salt, if it contains a sufficient
> amount of entropy.
>
> And to clairify what I said about the salt before... simply adding a salt
> will defeat rainbow attacks as Reto has already said, the added complexity
> of using a "hash function", of any kind, on the salt, does not significantly
> impact a dedicated attacker. Because in the situation of a database
> compromise the salt (which is assumably stored in the database, per user,
> and of sufficient entropy) has already been revealed, and the hash of it
> simply needs to be calculated once for the brute force attack on the
> password.
>
> Either way, the salt is a good addition. I'm pleased you guys are so
> proactive about security.
>
> However, if you are wishing to increase the security (time to brute
> force) of the password/salt entry it may be worthwhile to follow the
> following algorithm instead.
>
> sha2($salt + sha2($password + $salt))
>
> you can repeat that ad-naseum increasing the complexity of the brute force
> by forcing the attacker to follow the chained hash algorithm in their brute
> forcing attempts. You can even add multiple salts... Just don't store the
> final hash in the HTTP cookie like some of these other blogging platforms...
> On Tue, Mar 11, 2008 at 12:04 AM, Mark Wu <markplace at gmail.com> wrote:
>
> >  That's why I use (MD5($password)+MD5($salt)) to keep it easy to
> > upgrade.
> >
> > And use sha256() to enhence the security level.
> >
> > Mark
> >
> >  ------------------------------
> > *From:* plog-svn-bounces at devel.lifetype.net [mailto:
> > plog-svn-bounces at devel.lifetype.net] *On Behalf Of *Matt Wood
> > *Sent:* Tuesday, March 11, 2008 3:23 AM
> >
> > *To:* LifeType Developer List
> > *Subject:* Re: [pLog-svn] Salted MD5
> >
> >   The only reason you would salt passwords in a database means your
> > concerned that the password db table has been compromised... if you fear
> > that has happened then the salt that your storing in the database is
> > available to the attacker. Thus adding md5 or sha1 or sha256 of that salt to
> > the password is no more secure than just appending the salt in plaintext.
> > The same number of computations will be required to "crack" the password
> > hash.
> >
> > -Matt
> >
> > PS. md5/sha1 are not cryptographically secure hash algorithms anymore
> > (however probably are ok for this situation). any sha2 algorithm (sha256,
> > sha512) is suposedly.
> >
> > On Mon, Mar 10, 2008 at 11:32 AM, Mark Wu <markplace at gmail.com> wrote:
> >
> > > >
> > > >       How much more secure is than simply:
> > > >
> > > > md5($password . $private_key)
> > >
> > > Actually, it's no difference for normal people, but much secure for
> > > those
> > > hackers...
> > >
> > > BTW, VBB and IPB use:
> > >
> > > md5(md5($password).md5($private_key))
> > >
> > > >
> > > > And are there any downsides of the new method - ie. will it
> > > > fail on upgrades, or fail for certain servers, etc?
> > > >
> > >
> > > mmm .... for lifetype 2.0 . The minimal requirement is php 5.1.x ...
> > >
> > > so, It won't be a problem.
> > >
> > > mhash become "hash" in pecl in php5, if there is no hash installed, it
> > > will
> > > use the pure php  implementation...
> > >
> > > >
> > > > On Mon, 10 Mar 2008, Mark Wu wrote:
> > > >
> > > > > Here comes more secure algorithm:
> > > > >
> > > > > sha256(md5($password)+md5($your_provide_private_key));
> > > > >
> > > > > I use sha256 here.
> > > > >
> > > > > Here also comes the pure php sha256 implementation:
> > > > >
> > > > > http://nanolink.ca/pub/sha256/
> > > > >
> > > > > If the server has "hash" pecl, it will use it instead of
> > > > the pure one.
> > > > >
> > > > > Mark
> > > > >
> > > > >> -----Original Message-----
> > > > >> From: plog-svn-bounces at devel.lifetype.net
> > > > >> [mailto:plog-svn-bounces at devel.lifetype.net] On Behalf Of Reto
> > > Hugi
> > > > >> Sent: Monday, March 10, 2008 7:25 PM
> > > > >> To: LifeType Developer List
> > > > >> Subject: Re: [pLog-svn] Salted MD5
> > > > >>
> > > > >> Hi Mark
> > > > >>
> > > > >> I welcome your suggestion and think that this is valuable
> > > > >> protection against rainbow table attacks.
> > > > >>
> > > > >> We already had an issue with the revealed admin password
> > > > >> hash. This would have been less severe with the saltet md5.
> > > > >>
> > > > >> Thanks for suggesting!
> > > > >>
> > > > >> reto
> > > > >>
> > > > >> Mark Wu wrote:
> > > > >>> Hi All:
> > > > >>>
> > > > >>> I plan to upgrade our password algorithm to salted MD5, take the
> > > > >>> following for eaxample:
> > > > >>>
> > > > >>> sha1(md5($password) + user_defined_private_key);
> > > > >>>
> > > > >>> I will also remain an option in lifetype admin panel for
> > > > >> user to use
> > > > >>> the old MD5 way to keep compatability.
> > > > >>>
> > > > >>> If we use the algorithm above, It is also possible to
> > > > >> convert the old
> > > > >>> hashed password to new hased password.
> > > > >>>
> > > > >>> How do you think?
> > > > >>>
> > > > >>>
> > > > >>
> > > >
> > > http://kuza55.blogspot.com/2006/10/online-reverse-lookup-tables-for.ht
> > > > >>> ml
> > > > >>>
> > > > >>> These kind of online reverse lookup table sites making
> > > > the MD5 only
> > > > >>> algorithm more dangerous.
> > > > >>>
> > > > >>> Mark
> > > > >>>
> > > > >>>
> > > > >>>
> > > > >>>
> > > > >>>
> > > > >>
> > > >
> > > ----------------------------------------------------------------------
> > > > >>> --
> > > > >>>
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> > > > >>
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> > > >
> > > > --
> > > > Jon Daley
> > > > http://jon.limedaley.com/
> > > >
> > > > We are all made different, but we are all sinners.
> > > > -- Jim Herron
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