[Zope] CoreSessionTracking-based LoginMethod for LoginManager

[Florent Guillaume]

> 1. Start with the data you want to store
> 2. Append identifying information, eg the IPs of the client and
>    server, and the current date/time.
> 3. Make a digest of this plus a secret string which only you know,
>    and append that as a fingerprint.

I rewrite you 3. as computing as a fingerprint:
        H(known-string || password).

This construction apparently still has some very slight cryptographic
weaknesses. Lifted from bugtraq sometime ago:

    From: Michael Wojcik <Michael.Wojcik@merant.com>
    Date: Mon, 16 Jul 2001 10:45:48 -0700

    Schneier cites a private communication with Bart Preneel (author of
    RIPE-MAC) on possible weaknesses of the obvious constructions

	    H(known-string || password)
	    H(password || known-string)
	    H(password || known-string || password)
	    H(password-1 || known-string || password-2)

    and suggests one of the following instead (rewritten as password
    hashes):

	    H(password-1 || H(password-2 || known-string))
	    H(password || H(password || known-string))   [ie. pw-1 == pw-2]
	    H(password || pad || known-string || password)
                                                     [pad pw to full block]

    The simplest of these, in terms of retrofitting existing systems
    that use one of the constructions Ishikawa mentions, is

	    H(password || H(password || known-string))


So I'd use that last one instead.


Florent Guillaume
Nuxeo