Re: [CGA-EXT] One more bit for hash information in CGAs? ( was [Fwd: [BEHAVE] Modified EUI-64 format]

[Sheng Jiang <shengjiang at huawei.com>]

Agreed. I think it is useful. Since the hash length is really limited, every
bit is cherish and important. One more bit means, in average, attackers have
to double their efforts in order to break the same CGA. This update suits
CSI charter well as we target to update SEND and CGA specifications from the
beginning of this CSI WG.

The only issue we need to solve is the complicite backwards compatibility.
Since we cannot indicate whether this is CGAv1 without g bit or CGAv2 with b
bit, we may have to fully abandon CGAv1 in the updating process. Personally,
I think it is fine through it requests all existing implementation changed.

Best regards,

Sheng

> -----Original Message-----
> From: cga-ext-bounces at ietf.org 
> [mailto:cga-ext-bounces at ietf.org] On Behalf Of marcelo bagnulo braun
> Sent: Tuesday, July 07, 2009 2:58 AM
> To: cga-ext at ietf.org
> Cc: Dave Thaler
> Subject: [CGA-EXT] One more bit for hash information in CGAs? 
> ( was [Fwd: [BEHAVE] Modified EUI-64 format]
> 
> There is an ongoing discussion in BEHAVE ml, where it seems 
> that we could use the "g" bit in order to include hash information...
> considering that the hash length is one of the key 
> limitations of CGAs, we may consider updating 3972 to use this bit...
> comments?
> 
> I attach the extract of the thread below...
> 
> -------- Mensaje original --------
> Asunto: 	[BEHAVE] Modified EUI-64 format
> Fecha: 	Thu, 2 Jul 2009 04:06:21 +0000
> De: 	Dave Thaler <dthaler at windows.microsoft.com>
> Para: 	Xing Li <xing at cernet.edu.cn>
> CC: 	Behave WG <behave at ietf.org>
> 
> 
> 
> Similarly, with privacy addresses referred to in the draft 
> quote at top, RFC 3041 section 3.2.1 point 3 forces the 
> randomized interface identifier to adhere to this 
> requirement, so that it's a 63-bit random number, not a 
> 64-bit random number.  And with CGAs, RFC 3972 section 4 
> point 6 similarly forces a generated interface identifier to 
> adhere to this requirement. (As an aside, it also reserves 
> the "g" bit which is actually unnecessary since it's not IEEE 
> EUI-64-derived.  RFC 4291 only discusses the "g" bit for 
> addresses derived from IEEE EUI-64's, which is why RFC 3041 
> and a translation format can still use that bit).
> 
> 
> 
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