forms and secure authentication

[Brad Marsh]

Eric (and Brian),

As I looked through my documentation, I realized that I had realized that. I
had been doing Eric's #3, but switched to #1 - kind of. I store a hash that
is the md5 of a (md5(password) + salt). I did this because if the database
is compromised the passwords are already obfuscated.

Brad

----- Original Message -----
From: "Eric Soroos" <eric-ul at soroos.net>
To: <Frontier-Users at userland.com>
Sent: Thursday, November 21, 2002 12:44 PM
Subject: Re: forms and secure authentication


>
> > >Auth Scheme
> > >Person logs in with username "username", password "greatPassword".
> > > Web page javascript creates MD5 has from password before sending to
server.
> > >Only encrypted password is sent, and that only once.
>
> >
> > This really isn't any more secure than simply sending the password in
the
> > clear.  (The one advantage is that for people who use the same password
for
> > many different services, a successful attacker could impersonate them
only
> > for this service, and would not gain the actual password which could be
> > used elsewhere.  So this is a step better than sending a cleartext
> > password.)
>
> If you're going to write login algorithims that rely on some for of
hashing or encryption, PLEASE look at relevant RFCs for similar services so
that you don't get bitten by subtle of not so subtle bugs.
>
> Maybe I should rephrase that. If you're going to create algorithims that
use crypto, please look at current practice.
>
> Some things that you may want to worry about:
>
> Replay attacks, both login and cookie.
> Comprimised clients.
> Cleartext transmission of password.
> Transmission of password equivalents.
> Effect of NAT/Proxy gateways.
>
> In general, you have 4 options:
>
> 1) store plaintext pw, transmit hash(pw + salt), hash your copy of the pw
with the salt and compare.
> 2) store hash(pw + salt) transmit plaintext pw, hash it with salt and
compare.
> 3) store plaintext pw, transmit plaintext pw, compare. (What you're doing
currently)
> 4) More complicated systems like challenge-response, certs, etc.
>
> Of course, where I sey transmit plaintext, that may be through an ssl
tunnel, in which case it's only plaintext to the server, not to snoopers.
>
> eric
>
>
>