Re: [decade] Open Issue-3 (draft "An HTTP-based DECADE ResourceProtocol")

Stephen Farrell <stephen.farrell@cs.tcd.ie> Tue, 18 September 2012 08:57 UTC

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Date: Tue, 18 Sep 2012 09:57:53 +0100
From: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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To: Peng Zhang <pzhang.thu@gmail.com>
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Cc: "DECADE@ietf.org" <DECADE@ietf.org>
Subject: Re: [decade] Open Issue-3 (draft "An HTTP-based DECADE ResourceProtocol")
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On 09/18/2012 09:48 AM, Peng Zhang wrote:
> Exactly, the probability would be negligible. Even if we use the trunked hash, say 32 bit, it would suffice too.

Not sure about that. For collisions you need to think about the
birthday problem, so a 32 bit hash may mean a 2^-16 collision
probability which is probably too high in many cases.

Either don't truncate at all or think deeply about it first is
the right approach I'd say.

S.

> BR,
> 
> Peng.
> 
> On Sep 18, 2012, at 4:34 PM, Stephen Farrell wrote:
> 
>>
>>
>> On 09/18/2012 08:08 AM, Songhaibin wrote:
>>> Hi Peng,
>>>
>>> "Low" does not mean no existence. I'm wondering if two different objects are happened to have the same name at the same DECADE server, or at different DECADE servers with different service providers (we require the name to be global unique), we should have a collision avoidance mechanism for it.
>>
>> The existence of SHA256 collisions would be news that would make
>> CNN and BBC probably (after they picked it up from /.:-). In
>> this case "low" is practically the same as non-existent if you
>> use all the bits of SHA256.
>>
>> S.
>>
>>> -Haibin
>>>
>>>
>>> From: Peng Zhang [mailto:pzhang.thu@gmail.com]
>>> Sent: Tuesday, September 18, 2012 2:10 PM
>>> To: Songhaibin
>>> Cc: Rahman, Akbar; Wangdanhua; DECADE@ietf.org
>>> Subject: Re: [decade] Open Issue-3 (draft "An HTTP-based DECADE ResourceProtocol")
>>>
>>> Hi Haibin,
>>>
>>>     I don't quite understand your question. If we are using SHA-256, as suggested in draft-farrell-decade-ni, the probability that two different objects have the same name would be very low.
>>>
>>> BR,
>>>
>>> Peng.
>>>
>>> On Sep 17, 2012, at 5:42 PM, Songhaibin wrote:
>>>
>>>
>>> While many people advocate Hashed names, the key point is, shall we allow conflict for the names? If we do not allow, how to solve it.
>>>
>>> BR,
>>> -Haibin
>>>
>>> From: decade-bounces@ietf.org<mailto:decade-bounces@ietf.org> [mailto:decade-bounces@ietf.org] On Behalf Of Rahman, Akbar
>>> Sent: Wednesday, September 12, 2012 10:31 PM
>>> To: Wangdanhua
>>> Cc: DECADE@ietf.org<mailto:DECADE@ietf.org>
>>> Subject: Re: [decade] Open Issue-3 (draft "An HTTP-based DECADE ResourceProtocol")
>>>
>>> Hi Danhua,
>>>
>>> Yes, I agree that to make progress on your draft you need to show how to use a naming scheme as part of your proposal.  And I also agree that using the draft-farrell-decade-ni should be the starting point.
>>>
>>>
>>> Sincerely,
>>>
>>>
>>> Akbar
>>>
>>> From: decade-bounces@ietf.org<mailto:decade-bounces@ietf.org> [mailto:decade-bounces@ietf.org] On Behalf Of Wangdanhua
>>> Sent: Wednesday, September 12, 2012 2:13 AM
>>> To: DECADE@ietf.org<mailto:DECADE@ietf.org>
>>> Subject: [decade] Open Issue-3 (draft "An HTTP-based DECADE ResourceProtocol")
>>>
>>>
>>> Hi all,
>>>
>>> The following is the third open issue left for "An HTTP-based DECADE Resource Protocol" (draft-wang-drp). We're looking forward to your opinions and comments.
>>>
>>> About the object naming scheme used in DECADE Protocol, we're inclined to adopting the naming scheme proposed in the draft-farrell-decade-ni (Naming Things with Hashes). We thought it's a good scheme and we are planning to have a try and see whether it's workable in the protocol we proposed.
>>>
>>> Does anybody have other opinions? And we'd like to hear your voice.
>>>
>>> Best wishes,
>>> Danhua Wang
>>>
>>>
>>>
> 
> 
>