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>From: "Hannes Tschofenig" <>
>To: "'Art Botterell'" <>,
> <>
>Date: Thu, 12 Mar 2009 23:11:01 +0200
>Thread-Index: AcmjVNtiQzITaJ5ORimIxcf69zRfLQAATPCA
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>Subject: Re: [CAP] Then Again... (was Re: CAP Security
> UsingDigitalSignatures)
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>Hi Art,
>
>>On Mar 12, 2009, at 3/12/09 1:17 PM, Hannes Tschofenig wrote:
>>> What does it mean if you have authenticated the message sender?
>>> Would this tell the user a lot?
>>
>>It would indeed. For human recipients the credibility of the
>>source is one of the chief factors in warning message
>>effectiveness. And do we expect automated systems to sound
>>sirens or interrupt broadcasts or ring cellphones without
>>being able to determine that the message is intact and
>>authentic and verifiably from a source that can be held
>>accountable? Not likely.
>
>Most systems (even the systems that are being standardized today) are based
>on the assumption of hop-by-hop security).
>
>No digital signature does not mean no security; just means different
>security mechanisms.
>
>>
>>> If you cannot verify the signature do dump the message?
>>
>>Depends on the circumstance, but in many cases (see above) the
>>answer would be "yes"... if a message can't be attributed to a
>>particular source, or if that source isn't considered
>>authoritative according to
>>the recipient's own policy, then that message may well be ignored.
>>Depends on the costs of a "false positive"... for something
>>like a server outage alert, they may be low and such
>>safeguards excessive, but for a large-scale public warning
>>application they're politically essential.
>>
>>As for a PKI... we've been experiencing a chicken-and-egg
>>deadlock for a number of years now. Without implementations
>>that use digital signatures, there's been no demand for a PKI.
>> And many implementers have been waiting for someone to
>>establish a PKI before they start developing such
>>implementations. Fortunately, it's possible develop and
>>demonstrate such implementations on a limited scale without
>>requiring a full-blown PKI, so that's the end of the string I
>>suggest we tug on first.
>>
>>Personally I'd very much like to see a membership-based
>>organization like COMCARE take the lead in deploying a PKI for
>>public safety users. But we don't have to wait for the
>>perfect before we experiment with the good.
>
>Sure, it would be nice to have those things in place but getting there is
>tough.
>If you use the trust anchors already available in the browser then you could
>deploy something that may work but obviously you wouldn't get the same
>guarantees as in a case where you have those entities distributing warnings
>also being accredited (for example, by COMCARE or ITU-T) in order to get a
>certificate.
>
>Ciao
>Hannes
>
>
>>- Art
>>
>>
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