From: <[email-masked]>
Date: Mon, 4 Aug 2003 12:55:34 +0300

> While the CGA specification for SEND only talks about
> the uses of CGA in SEND, there are other protocols that
> will use the same CGA keys and addresses. This raises 
> the question of related-protocol attacks. In such attacks, 
> CGA-signed messages from one protocol could be replayed
> in another protocol.

Yes. We need to ensure that the messages are indeed
different when they are signed.

> This tag could
> either be a short (e.g. 32-bit) IANA-allocated value or 
> a fixed 128-bit number chosen randomly by us at the protocol 
> design time. The IANA-allocated type tags are more in line 

I'd prefer IANA allocation, but we can start by
giving SEND a random number in this allocation to
reduce the chance of a collision. Say, SEND =
0x1E7F 2003 5E2D C5A1 500D F00D 802E BEE2.

Since the value is not communicated over the wire, it can
be of any length. 

> There is also the editorial question of whether the type
> tag should be part of the CGA or SEND document. If it is
> an IANA-allocated short value, then it seems the CGA documents 
> should define a new IANA registry and the SEND document 
> should define an entry in the registry. 

Sounds good.

> Define a randomly chosen 128-bit tag for each SEND message
> type (NS, NA, RS, RA, Redirect). Define these tag values in 
> the SEND document. One of these 5 tags should be prepended 

Current document includes the whole packet under the digital
signature. This includes therefore also the ICMP Type. Would
that be sufficient with a single tag value for SEND?

--Jari

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