[whatwg] Proposal for secure key-value data stores

Jonas Sicking jonas at sicking.cc
Wed Apr 7 17:09:44 PDT 2010

On Wed, Apr 7, 2010 at 4:54 PM, Jeremy Orlow <jorlow at chromium.org> wrote:
> On Thu, Apr 8, 2010 at 12:48 AM, Jonas Sicking <jonas at sicking.cc> wrote:
>> On Wed, Apr 7, 2010 at 4:29 PM, Jeremy Orlow <jorlow at chromium.org> wrote:
>> >> > In regards to data expiration, part of ensuring the security of data
>> >> > is
>> >> > knowing how long it will be stored on disk. If I let someone borrow
>> >> > my
>> >> > computer to check their email, and the email client happens to save
>> >> > some
>> >> > data onto the client, then that person’s data will now be on my disk
>> >> > for
>> >> > who
>> >> > knows how long. That represents a data security issue. By allowing an
>> >> > expiration date to be tied to the data, you can have reasonable
>> >> > assurance
>> >> > that the data isn’t just going to be sitting around waiting for
>> >> > someone
>> >> > to
>> >> > try and use it.
>> >> >
>> >>
>> >> It is true that not having control over your data could be an issue,
>> >> but
>> >> simply
>> >> embedding expiry into the data may not buy you much to protect it.
>> >> Insofar
>> >> as the crypto wouldn't be running in a TPM, it would be easy to reverse
>> >> engineer
>> >> it and extract the data; it would also be fairly easy to reset the
>> >> clock on the device
>> >> to keep data from being deleted.
>> >
>> > One thing that might be interesting is a way to cache large amounts of
>> > data
>> > that are deleted when the browser and/or tab closes.  This might be
>> > something for the new file system API to consider (hence adding ericu to
>> > the
>> > thread).  But time based controls aren't going to do anything more than
>> > give
>> > perceived security.  (In your use case, expiration doesn't add much
>> > actual
>> > security for the reasons Dirk mentioned.)
>> I disagree. Having data time out is a good "additional layer" of
>> security. For example if your laptop gets stolen, then it's much
>> better if the thief only gets access to the sites you've used the last
>> 24h, than any site you've ever used.
>> This is why people do things like enforce password changes every X
>> weeks. Yes, password changing has social downsides, like people
>> writing down passwords on post-its etc. However those problems do not
>> seem to apply here.
>> So I don't think anyone is arguing that expiration is good security in
>> and of itself. But it is a good (and low cost) way of getting
>> additional security.
> Sure, but it should not be thought of as anything more than a hint.  If I go
> to a site that says expire the data in 24 hours and then I turn it off and
> don't use it for a year, that data is still there.

This is true, and important.

> Anything that has the outward appearance of adding more security than it
> actually does worries me.  (I'm obviously worried a lot. :-)

I think it's pretty obvious though that expiring the data X seconds in
the future doesn't in and of itself give any protection what so ever
until the data has actually been expired.

I guess it could be argued that it isn't obvious that the data is only
expired if the browser is running. I don't think this is enough of a
problem to kill the feature though.

/ Jonas

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