Re: [hiprg] use of sha-1 in the DHT interface draft

Tobias Heer <heer@cs.rwth-aachen.de> Fri, 21 October 2011 16:04 UTC

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From: Tobias Heer <heer@cs.rwth-aachen.de>
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Date: Fri, 21 Oct 2011 18:04:51 +0200
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To: "Henderson, Thomas R" <thomas.r.henderson@boeing.com>
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Subject: Re: [hiprg] use of sha-1 in the DHT interface draft
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Am 21.10.2011 um 17:33 schrieb Henderson, Thomas R:

> 
> 
>> -----Original Message-----
>> From: Ahrenholz, Jeffrey M
>> Sent: Friday, October 21, 2011 8:00 AM
>> To: Henderson, Thomas R; hiprg@irtf.org
>> Subject: RE: use of sha-1 in the DHT interface draft
>> 
>>> However, my understanding is that the DHT server does not enforce the
>>> use of SHA-1; modified clients (that are HIP-aware) could use SHA-256
>>> truncated to 160 bits.
>> 
>> The DHT server does use SHA-1 internally to process removes. If the
>> client uses another hash function, the secret given in the DHT remove
>> will not match the SHA-1 hash used in the put.
> 
> I did not catch that detail since it is not very clear from the API document, but it makes more sense that it operates that way.
> 
>> 
>> The draft does not currently require a modified OpenDHT/Bamboo server.
>> It states in sections 3 and 7 that the server MAY/SHOULD be modified
>> for signature and host ID verification (it looks like the "MAY" in
>> section 3 should be changed to "SHOULD".)  Use of another hash
>> algorithm would require further server modifications (and specifying an
>> interface that deviates from OpenDHT.)
>> 
>>> - keep the draft as is, citing that OpenDHT interface prescribes SHA-
>> 1,
>>> and that the other usage of SHA-1 is not trying to obtain any crypto
>>> properties.  However, the implication of this is we will need to add
>>> more text in the security section and elsewhere to defuse this "red
>>> flag"
>> 
>> I would prefer the above option. The security considerations section
>> can include text about deviating from the OpenDHT interface in order to
>> support other hash functions. The original intent of the draft was to
>> re-use the freely-available OpenDHT interface in an interoperable
>> fashion.
>> 
> 
> In light of the above, I would lean towards your recommendation as well.  
> 
+1
Same here. If compatibility is an issue, it outweighs the other reasons. Having an API that is incompatible to the system makes little sense.

Tobias

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Dipl.-Inform. Tobias Heer, Ph.D. Student
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RWTH Aachen University, Germany
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