Subject: RE: [Mip6] Security Section Comments ondraft-ietf-mip6-bootstrap-ps-01.txt

From: [email-masked]
Date: Mon, 21 Feb 2005 07:55:56 +0200

Hi James,

> This note contains comments on Section 9, Security Considerations.
> 
> As a high level comment, this section seems to mix security considerations
> regarding the results of the bootstrapping process with security
> considerations for the bootstrapping process itself. This is somewhat
> confusing. Even though the two are related, I think the two need to be
> separated for clearer understanding. Furthermore, the bullet
> list at the end of the section contains a mix of design considerations
> and solutions. The solutions seem to me to be inappropriate in a problem statement.
>
> Finally there isn't any threat analysis and it seems to me that
> a problem statement security considerations should contain a threat
> analysis. Below is some suggested text that addresses these issues.
 
Generally I agree with your proposal, and I think the text improves
upon the current text.  One bit confused me:

> In addition to these attacks, there are other considerations that are
> important in achieving a good security design. Because mobility and network
> access authentication are separate services, any keys for these services
> need to be cryptographically separate, separately named, and have separate
> lifetimes that are not exceeded. This is necessary because a mobile host
> must be able to move from one serving (or roaming) network access provider
> to another without needing to change its mobility access provider. Finally,
> basic cryptographic processes must provide for multiple algorithms in order
> to accommodate the widely varying deployment needs.

Could you more fully explain this statement.

	Because mobility and network access authentication are separate services ...

One one level, in some deployments, these are indeed seperate.  However, in some,
you want fate-sharing between the two - if either fails, the other should fail.
Since mobility is needed (in some deployments) network access authentication
is not sufficient.  

However, I think you might be suggesting that the network access provider may be
seperate from the mobility access provider, therefore they keying material needs
to be seperate.  Is this more along the lines of what you mean?

John

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From: "James Kempf" <[email-masked]>
Date: Tue, 22 Feb 2005 10:59:37 -0800

Hi John,

>to be seperate.  Is this more along the lines of what you mean?

Actually, I think we want to keep the keys separate even if the network
access provider and mobility service provider are the same. From a security
standpoint, it makes sense to maintain separate keys, so that if one is
compromised the other won't be.  I suppose one could argue that "well, if
the network access service is compromised, the user is so hosed, so it
really doesn't matter if mobility service is compromised" but the othe way
around is something different. If the mobility service key is compromised,
the mobile host could stay put at the same place and re-establish secure
mobility access service, as long as network access service is not
compromised. If the two keys are the same, then the mobile host must go
through re-establishing secure network access service before mobility
service security can be repaired.

Does this make sense? If so, perhaps the draft should make this point
explicitly.

            jak