OpenSAML user discussion

[Derek Atkins <>]

"Scott Cantor" 
<>
 writes:

>> How do you do your symmetric key exchange?  In particular, how do you get
>> the shared secret between the subject (the user) and the SP (the service)?
>
> How does Kerberos do it? By hashing a password into a key, right? Have the
> authority issue an assertion with the confirmation key wrapped in the
> principal's key, then the principal enters the password, the client decrypts
> the confirmation key and uses it to generate the proof of posession to
> confirm itself as the subject to the SP.

No, there's no pre-shared secret between the user and the SP, just between
the user and the KDC.  The user makes a request of the KDC to authenticate
to the SP, and the KDC replies with (effectively):

  E({ K_ses, E({ username, service name, timestamp, K_ses }, K_kdc_sp) }, 
K_user)

The user can decrypt this and obtain the ticket and session key with
the SP, and then can use the K_ses to prove this isn't a replay.

> I'm sure there are lots more details to get right. I'm not advocating doing
> it, I'm just saying it's technically possible.

Sure, but at this point you're re-inventing kerberos; why would you
want to do that instead of just using RFC1510bis?

> -- Scott

-derek

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       

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