Re: [Mobopts] Review of draft-irtf-mobopts-location-privacy-solutions-06

Vijay Devarapalli <vijay.devarapalli@azairenet.com> Wed, 07 November 2007 00:06 UTC

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Date: Tue, 06 Nov 2007 16:06:22 -0800
From: Vijay Devarapalli <vijay.devarapalli@azairenet.com>
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To: Rajeev Koodli <rajeev.koodli@nokia.com>
Subject: Re: [Mobopts] Review of draft-irtf-mobopts-location-privacy-solutions-06
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Rajeev Koodli wrote:
> Hi Vijay,
> 
> 
> On 11/5/07 3:28 PM, "ext Vijay Devarapalli"
> <vijay.devarapalli@azairenet.com> wrote:
> 
>> Hello,
>>
>> I reviewed the draft. It still needs a lot of work.
>>
>> Section 4.1
>> -----------
>> Section 4.1 is not making sense to me. The pseudo home address
>> changes every time return routability is run. It also changes
>> every time the CoA changes. Why does it have to change so often?
>>
>> Isn't one pseudo home address per session with a correspondent
>> node sufficient?
>>
> 
> The pseudo HoA changing at each run of the RR provides some protection
> against profiling. Change of CoA upon handover, or a new CoA nonce index or
> a new RFC 3041 style CoA configuration makes a round of RR to be run. The
> pseudo HoA itself is not inducing new signaling, but a few computational
> steps.

Ok, but I am questioning the need for changing the pseudo home
address every time the return routability signaling is done
(every 420 seconds).


>>>    When a correspondent node receives a Binding Update with a new
>>>    destination option carrying the pseudo home address, it must first
>>>    compute Kpm as above.
>> You probably meant "a destination option carrying a new pseudo home
>> address". The home address destination option is always present in
>> the BU.
>>
> Actually, there is a new Type number for the Destination Option containing
> the pseudo HoA, so that the CN can first compute the String and recover the
> HoA.

Ok, got it. You would need add this new destination option to
the IANA considerations section. It is empty currently.

>>>    The privacy management key Kpm can be the same as the binding
>>>    management key Kbm and the mobile node generates the pseudo home
>>>    address as follows:
>>>
>>>       pseudo home address = Enc(Kpm, home address)
>>>
>>>       Where Enc(.) is a symmetric key encryption algorithm, for example,
>>>       AES.
>> hmm... You would need to pick *an* encryption algorithm and convey
>> the same to the CN. How would both ends pick the same algorithm
>> otherwise?
> 
> Right.

How is the information about the encryption algorithm conveyed?

>> Section 5
>> ---------
>> I am not sure why section 5 is needed at all. There is absolutely
>> no need to generate a pseudo home address with the home agent. The
>> MN can always use ESP in tunnel mode for MIPv6 signaling messages
>> and hide the home address from the access link. I suggest removing
>> sections 5.1, 5.2 and 5.3.
>>
> 
> You mean in relation to Section 4, this offers no additional benefits?

More fundamental than that. Why would the mobile node want to use a
pseudo home address with its home agent?

Vijay

> 
> Thanks for the review.
> 
> -Rajeev


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