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List:       ipsec
Subject:    Re: Re: question about Nonce
From:       Derek Atkins <warlord () mit ! edu>
Date:       2001-10-21 12:49:45
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Sorry, you are correct.  The cookie is reachability.  The nonces
are used to derive the session key.  The nonces should be used
ONLY ONCE.  This means that each phase-i and each phase-ii nonce
should be generated independently.

-derek

dxh <sleepy-cat@263.net> writes:

> =09you still did not tell if the nonce in phase one and the one in=
>  phase two is
> the same. And I think the cookie is not the nonce. It's cookie's=
>  reachability, not
> nonce's, that is tested.
> =09I am a newbie in security area. Maybe I miss your point. Would=
>  you give more 
> detail?
> 
> 
> 
> you writes:
> >The nonce provides a quick, non-cryptographic check to prevent=
>  not
> >only replay but also DoS attacks.  The responder should not have=
>  to
> >perform any high-CPU operations (e.g. modexp) until the nonce=
>  (cookie)
> >reachability test has succeeded.
> >
> >-derek
> >
> >dxh <sleepy-cat@263.net> writes:
> >
> >> =09I am not sure if the nonce in Phase One is the same as 
> >> the one in Phase two. And I still can not see why there is 
> >> need using nonce to prevent from replay attacking in Phase 
> >> One. I think the Kes of DH exch can do this.
> >> 
> >> 
> >> 
> >> Dong Xiaohu
> >> 
> >
> >-- 
> >       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
> >       warlord@MIT.EDU                        PGP key available
> 
>                     =D6=C2
> =C0=F1=A3=A1
> 
>             dxh
>             sleepy-cat@263.net
> 

-- 
       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
       warlord@MIT.EDU                        PGP key available

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