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
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