Re: [therightkey] Will the real RPF please stand up?

[Stephen Kent <[e-mail]>]

At 8:22 PM -0500 2/8/12, Phillip Hallam-Baker wrote:
>Alice has three mobile phones and six laptops.
>
>Using embedded keys in those devices for authorization is no problem
>since each device can have a separate private key and the
>authentication server tracks the fact that there are nine devices that
>might authenticate Alice.
>
>The same model can even be made to work for confidentiality. Alice can
>read her DRM protected Kindle content on any one of those devices.
>(Though there may be limits on how many devices the DRM scheme will
>permit).
>
>
>Trying to make S/MIME email work in that scenario is futile. The
>sender only tracks one private key for Alice. So Alice has to export
>her private key to all her S/MIME clients. Not only is that terrible
>security practice, it is too much work. Worse, Alice has to repeat the
>process once a year.
>
>That is why I no longer believe that end-to-end is a desirable
>quality. A security requirement that does not consider the cost it
>imposes versus the risks it mitigates is ideology.

OK, now I understand your argument (aided by 5 paragraphs explanatory of text).

If this is the major issue, then, for the S/MIME context, one could
develop procedures for easy, secure xfer of private keys between 
devices, so that Alice could have the same key for encryption (more 
properly decryption)
for S/MINE. Procedures for doing this have been proposed in secruity 
conferences for at least a decade. Aslo, this is an issue only for 
encrypted S/MIME
messages, not signed messages. Outside of enterprise contexts I 
rarely see encrypted messages, and I don't think the problem you 
cited is the primary'
reason for this.

Steve