RE: de-identification text for Wednesday's call

Dan,

As with HIPPA, I believe differentiated treatment of internal and external datasets is appropriate as this changes the risk profile of re-identification - again, the root of the conversation being a "risk-based" approach versus a totalitarian approach as you suggest.  My solution meets the perceived consumer harm in this case - yours of course does as well but goes far too far over the top of what is actually needed.  If your goal is to create a compromise end-point that will likely be implemented by industry then my recommended approach gets us there.  If you'd like to instead stand by absolutist approaches, that is of course your prerogative and we'll have those removed through the standard W3C process.  I'm simply trying to save everyone some time and get to a meaningful outcome quickly.

- Shane

From: Dan Auerbach [mailto:dan@eff.org]
Sent: Tuesday, April 02, 2013 12:21 PM
To: public-tracking@w3.org
Subject: Re: de-identification text for Wednesday's call

Shane,

Why hash at all in this case? If you are relying on operational and administrative controls, you might as well just pledge not to look up the cookie when you receive it. If you are rotating (and discarding) salts frequently, then it will have a positive effect, but otherwise I don't think hashing provides any benefit here.

But this is an aside to our main disagreement about the larger issue about the role that operational and administrative controls should play. I agree that they should play a role, but only after de-identification of data has been achieved. If the result of a DNT:1 request is business as usual, with minor scrubbing and the caveat that only 4000 engineers at a large corporation get default access to a specially marked database instead of 10000, then that will not be a successful standard. (Of course I welcome more detailed information about operational and administrative controls.)

One last point I wanted to make is that of course the data sets I mentioned refer to public data. We don't have access to internal corporate data sets. There are laws in place to protect the pilfering of that data, so of course no-one is going to steal data then publish an academic paper about it, effectively painting a big target on themselves for federal prosecutors and corporate legal teams. In light of this, the right empirical question to ask is: of large publicly available data sets that contain user data and are somewhat akin to log data, how often are there successful re-identification or attribute disclosure attacks? Can you point to any public data sets where such an attack has not been found?

If your argument is instead that public data should be treated differently from non-public data, then I'd suggest that this is out of scope for the DNT conversation. DNT is about giving users the choice to opt out of tracking by companies, which must entail meaningfully curbing data collection and retention by that company, not merely a request that a company not make public its collected data. (Indeed, in addition to being an excessively weak demand by the user, this would in some cases be a vacuous request, since making that information public is already prohibited by law.) The de-identification question exists within the scope of what the companies themselves can do with the data -- is the data de-identified with respect to the entity that collected the data?

Best,
Dan

On 04/02/2013 11:03 AM, Shane Wiley wrote:
Dan,

Once the one-way hash is applied (and other elements of record appropriately cleansed) the data is moved to a system that is not allowed to be accessed externally.  Its these operational and administrative controls that are essential to ensure de-identified data is not re-identified at some later time.  I believe you're looking only at the technical merits which is only seeing a small portion of the overall solution.

- Shane

From: Dan Auerbach [mailto:dan@eff.org]
Sent: Tuesday, April 02, 2013 10:59 AM
To: public-tracking@w3.org<mailto:public-tracking@w3.org>
Subject: Re: de-identification text for Wednesday's call

On 04/02/2013 08:50 AM, Shane Wiley wrote:
once the one-way hash function has been applied the data is never again able to be accessed in real-time to modify the user's experience.
I think I'm confused, can you explain this more? How is this possible? If you are just hashing a cookie string, your web server receives a request that includes a cookie string, you hash that cookie string (which is in incredibly fast operation), match the hashed cookie against the stored data, and return personalized results.

Or are you salting the hash differently for every request, or combining the cookie with an ephemeral piece of data (the timestamp) before hashing and then throwing away the timestamp?

Thanks for clarifying, apologies if I'm just being dense.

Dan




--

Dan Auerbach

Staff Technologist

Electronic Frontier Foundation

dan@eff.org<mailto:dan@eff.org>

415 436 9333 x134




--

Dan Auerbach

Staff Technologist

Electronic Frontier Foundation

dan@eff.org<mailto:dan@eff.org>

415 436 9333 x134