Microid mailing list

["Eran Sandler" <eran AT yedda.com>]

HMAC needs an underlying hashing function such as SHA256 or (the already
problematic) MD5 and SHA1.
It has the additional value of a secret key but it is still as strong as the
underlying hashing function.

As far as I understand HMAC, the key is needed in both places, the place the
generates the hash and the place that creates it to verify it.
This means it will raise problems in distributing this key in a secure
manner and will make it harder for implementers of microid and validation
implementers.

I think that by using just a hashing algorithm it should be fine and make
the code a lot easier to write for implementers.
The one thing we do need to give thought to is being able to replace the
hashing algorithm when (or if) it is not considered safe for usage anymore
(like SHA1 and MD5).

For that we will need the ability to describe the hashing function used,
just like Yaniv previously suggested, i.e.:

<meta name="microid"
       content="sha256:openid:e5de55ef248b5f8b06d38253cac0ae725d6455fb"/>

or, more correctly presented (after discussing it with Yaniv :-) ):

<meta name="microid"
       content="openid:sha256:e5de55ef248b5f8b06d38253cac0ae725d6455fb"/>

So that the data being hashing will be first, and then we will have the
hashing algorithm.

Eran


-----Original Message-----
From: microid-bounces AT lists.ibiblio.org
[mailto:microid-bounces AT lists.ibiblio.org] On Behalf Of Peter Saint-Andre
Sent: Tuesday, December 05, 2006 10:34 PM
To: yaniv AT yedda.com
Cc: microid AT lists.ibiblio.org
Subject: Re: [Microid] MicroID hashing algorithm(s) and normalization

<snip/>

Regarding HMAC, read this (user-friendly intro):

http://en.wikipedia.org/wiki/HMAC

HMAC is not a hashing algorithm like the SHA family, it is a Message
Authentication Code (MAC) function. So HMAC uses a secret key in the MAC
generation process. For our purposes the question is: whose secret key?
I guess for microid it would be the key of the entity that generates the
microid. So if I visit yedda.com or whatever, the microid is generated
by Yedda and so Yedda uses its key in the microid generation process.
(It could also use a key provided by the other party, naturally, but in
consumer-oriented applications that may be less likely to succeed.)

Thoughts?

Peter

-- 
Peter Saint-Andre
Jabber Software Foundation
http://www.jabber.org/people/stpeter.shtml