Subject: [Perc] Mirja Kühlewind's No Objection on draft-ietf-perc-private-media-framework-10: (with COMMENT)

From: Mirja Kühlewind via Datatracker <[email-masked]>
Date: Tue, 14 May 2019 04:12:07 -0700

Mirja Kühlewind has entered the following ballot position for
draft-ietf-perc-private-media-framework-10: No Objection

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COMMENT:
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Thanks for this well-written document.

Regarding the security considerations, I would think that the Key Distributor
is actually sometime like a central attack point, however, I don't think that
is really discussed in the security considerations section. Would it make sense
to add some more words there?

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From: "Paul E. Jones" <[email-masked]>
Date: Tue, 14 May 2019 23:53:01 +0000

Mirja,

Yeah, that is valid point.  We mentioned a time or two in the document 
how important it is to secure the Key Distributor, but explicit text 
that discusses that further might be appropriate here.  I've copied 
Vincent for his input, too, since he did have comments on other parts of 
the Security Considerations section.

I made a first draft of a new section.  I pasted it below.  Please let 
me know what you think.

Thanks,
Paul

8.3. Key Distributor Attacks

    As stated in Section 3.2.2, the Key Distributor needs to be secured
    since exploiting the Key Server can allow an adversary to gain access
    to the keying material for one or more conferences. Having access to
    that keying material would then allow the adversary to decrypt media
    sent from any endpoint in the conference.

    As a first line of defense, the Key Distributor authenticates every
    security association, both associations with endpoints and Media
    Distributors. The Key Distributor knows which entities are
    authorized to have access to which keys and inspection of
    certificates will substantially reduce the risk of providing keys to
    an adversary.

    Both physical and network access to the Key Distributor should be
    severely restricted. This may be more difficult to achieve when the
    Key Distributor is embedded within and endpoint, for example.
    Nonetheless, consideration should be given to shielding the Key
    Distributor from unauthorized access or any access that is not
    strictly necessary for the support of an ongoing conference.

    Consideration should be given to whether access to the keying
    material will be needed beyond the conclusion of a conference. If
    not needed, the Key Distributor's policy should be to destroy the
    keying material once the conference concludes or when keying material
    changes during the course of the conference. If keying material is
    needed beyond the lifetime of the conference, further consideration
    should be given to protecting keying material from future exposure.
    While it might be obvious, it is worth stating to avoid any doubt
    that if an adversary were to record the media packets transmitted
    during a conference and then gain unauthorized access to the keying
    material left unsecured on the Key Distributor even years later, the
    adversary could decrypt the content every packet transmitted during
    the conference.

------ Original Message ------
From: "Mirja Kühlewind via Datatracker" <[email-masked]>
To: "The IESG" <[email-masked]>
Cc: [email-masked]; [email-masked]; [email-masked]; 
[email-masked]
Sent: 5/14/2019 7:12:07 AM
Subject: [Perc] Mirja Kühlewind's No Objection on 
draft-ietf-perc-private-media-framework-10: (with COMMENT)

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