W3C home > Mailing lists > Public > public-tracking@w3.org > September 2012

RE: definition of "unlinkable data" in the Compliance spec

From: Shane Wiley <wileys@yahoo-inc.com>
Date: Fri, 21 Sep 2012 15:31:42 -0700
To: "rob@blaeu.com" <rob@blaeu.com>, "public-tracking@w3.org" <public-tracking@w3.org>
Message-ID: <63294A1959410048A33AEE161379C802620761D889@SP2-EX07VS02.ds.corp.yahoo.com>

We'll be having this debate till the end of time :-).  It depends on your definition of anonymous.  If anonymous means that a record identifier that cannot be linked directly to a person or device in the real world, them the approach I defined meets the bar of "anonymization".  If you feel that any identifier anywhere in the world regardless of its application in the real world as NOT being anonymous, then you'd come to the conclusion (albeit incorrectly in my opinion) that the approach I outlined arrives at a pseudonymous outcome.

- Shane

-----Original Message-----
From: Rob van Eijk [mailto:rob@blaeu.com] 
Sent: Friday, September 21, 2012 3:08 PM
To: public-tracking@w3.org
Subject: RE: definition of "unlinkable data" in the Compliance spec

>>  I don't believe the goal here is an absolutist one
> (aka "completed destruction of identifiers") and that is why 
> "commercially reasonable" is the appropriate outcome.

But Shane, do you share the view that a commercially reasonable outcome is still a pseudonomous outcome?


Shane Wiley schreef op 2012-09-21 19:16:
> Ed,
> I disagree with the concept of "easy to recover" as I'm not suggesting 
> hashing the individual octets but rather the entire IP Address (not a 
> single octet or individualized octet hashing) - especially as you 
> apply this to IPv6. With the appropriate level of access to raw and 
> hashed datasets, the necessary tools, and the intent, some 
> anonymization schemes can be hacked (dictionary attacks being the most 
> straight forward). I don't believe the goal here is an absolutist one 
> (aka "completed destruction of identifiers") and that is why 
> "commercially reasonable" is the appropriate outcome.
> - Shane
> FROM: Ed Felten [mailto:ed@felten.com]
> SENT: Friday, September 21, 2012 10:01 AM
> TO: Shane Wiley
> CC: Grimmelmann, James; <public-tracking@w3.org>
> SUBJECT: Re: definition of "unlinkable data" in the Compliance spec
> By the way, hashing IP addresses (with or without salting) does not 
> render them unlinkable. After hashing, it's easy to recovery the 
> original IP address. The story is similar for other types of unique 
> identifiers--there are ways to get to unlinkability, but hashing by 
> itself won't be enough.
> On Fri, Sep 21, 2012 at 12:01 PM, Shane Wiley <wileys@yahoo-inc.com 
> [1]> wrote:
> <Ed - apologies for not getting back to you sooner - I was on vacation 
> for the past week.>
> James,
> I like your approach the best and it was this perspective I was 
> intending when writing the text that Ed is questioning.
> The goal is to find the middle-ground between complete destruction of 
> data and an unlinkable state that still allows for longitudinal 
> consistency for analytical purposes BUT CANNOT be linked back to a 
> production system such that the data could be used to modify a single 
> user's experience.
> For example, performing a one-way secret hash (salted hash) on 
> identifiers (Cookie IDs, IP Addresses) and storing the resulting 
> dataset in a logically/physically separate location from production 
> data with strict access controls, policies, and employee education 
> would meet the definition of "unlinkable" I'm aiming for.
> - Shane
> -----Original Message-----
> From: Grimmelmann, James [mailto:James.Grimmelmann@nyls.edu [2]]
> Sent: Friday, September 21, 2012 8:14 AM
> To: Lauren Gelman
> Cc: Ed Felten; <public-tracking@w3.org [3]>
> Subject: Re: definition of "unlinkable data" in the Compliance spec
> I really like Lauren's suggestion. My only concern is that 
> "reasonably" and "reasonable" have so many different meanings in legal 
> settings that it could be ambiguous. Sometimes an action is 
> "reasonable" if a person who is ethical and cautious would do it:
> it's
> not reasonable to leave sharp tools lying around in a children's play 
> area, or to invest a trust fund in marshmallows. Sometimes it refers 
> to what a rational non-expert would believe about the subject, so a 
> court will uphold a jury verdict unless "no reasonable jury" could 
> have reached the conclusion it did. Sometimes it's about the norms and 
> expectations of an industry. An auction might need to be conducted in 
> a "commercially reasonable" way, which means for example giving enough 
> notice that there will be real competitive bidding, but not spending 
> more than the property is worth.
> I think this last sense is the most appropriate one in context. So 
> perhaps something like "data that cannot be associated with an 
> identifiable person or user agent through commercially reasonable 
> means." That is, the question would be whether a normal business with 
> normal resources and motivations would consider reidentifying the data 
> to be feasible.
> James
> --------------------------------------------------
> James Grimmelmann Professor of Law
> New York Law School (212) 431-2864 [4]
> 185 West Broadway james.grimmelmann@nyls.edu 
> [5]<mailto:james.grimmelmann@nyls.edu [6]> New York, NY 10013 
> http://james.grimmelmann.net [7]
> On Sep 20, 2012, at 7:22 PM, Lauren Gelman <gelman@blurryedge.com 
> [8]<mailto:gelman@blurryedge.com [9]>> wrote:
> Unlinkable data is data that cannot reasonably be associated with an 
> identifiable person or user agent.
> Lauren Gelman
> BlurryEdge Strategies
> 415-627-8512 [10]
> On Sep 18, 2012, at 8:05 AM, Ed Felten wrote:
> Sorry to repost this, but nobody has answered any of my questions 
> about Option 1 for the unlinkability definition.
> Note to proponents of Option 1 (if any): If nobody can explain or 
> clarify Option 1, that will presumably be used as an argument against 
> Option 1 when decision time comes.
> ---------- Forwarded message ----------
> From: Ed Felten <ed@felten.com [11]<mailto:ed@felten.com [12]>>
> Date: Thu, Sep 13, 2012 at 5:03 PM
> Subject: definition of "unlinkable data" in the Compliance spec
> To: "<public-tracking@w3.org [13]<mailto:public-tracking@w3.org
> [14]>>" <public-tracking@w3.org [15]<mailto:public-tracking@w3.org
> [16]>>
> I have some questions about the Option 1 definition of "Unlinkable 
> Data", section 3.6.1 in the Compliance spec editor's draft. The 
> definition is as follows [fixing typos]:
> A party renders a dataset unlinkable when it:
> 1. takes commercially reasonable steps to de-identify data such that 
> there is confidence that it contains information which could not be 
> linked to a specific user, user agent, or device in a production 
> environment [2. and 3. aren't relevant to my questions]
> I have several questions about what this means.
> (A) Why does the definition talk about a process of making data 
> unlinkable, instead of directly defining what it means for data to be 
> unlinkable? Some data needs to be processed to make it unlinkable, but 
> some data is unlinkable from the start. The definition should speak to 
> both, even though unlinkable-from-the-start data hasn't gone through 
> any kind of process. Suppose FirstCorp collects data X; SecondCorp 
> collects X+Y but then runs a process that discards Y to leave it with 
> only X; and ThirdCorp collects X+Y+Z but then minimizes away Y+Z to 
> end up with X. Shouldn't these three datasets be treated the 
> same--because they are the same X--despite having been through 
> different processes, or no process at all?
> (B) Why "commercially reasonable" rather than just "reasonable"? The 
> term "reasonable" already takes into account all relevant factors.
> Can
> somebody give an example of something that would qualify as 
> "commercially reasonable" but not "reasonable", or vice versa? If not, 
> "commercially" only makes the definition harder to understand.
> (C) "there is confidence" seems to raise two questions. First, who is 
> it that needs to be confident? Second, can the confidence be just an 
> unsupported gut feeling of optimism, or does there need to be some 
> valid reason for confidence? Presumably the intent is that the party 
> holding the data has justified confidence that the data cannot be 
> linked, but if so it might be better to spell that out.
> (D) Why "it contains information which could not be linked" rather 
> than the simpler "it could not be linked"? Do the extra words add any 
> meaning?
> (E) What does "in a production environment" add? If the goal is to 
> rule out results demonstrated in a research environment, I doubt this 
> language would accomplish that goal, because all of the 
> re-identification research I know of required less than a production 
> environment. If the goal is to rule out linking approaches that aren't 
> at all practical, some other language would probably be better.
> (I don't have questions about the meaning of Option 2; which shouldn't 
> be interpreted as a preference for or against Option 2.)
> Links:
> ------
> [1] mailto:wileys@yahoo-inc.com
> [2] mailto:James.Grimmelmann@nyls.edu
> [3] mailto:public-tracking@w3.org
> [4] http://roundcube.xs4all.nl/tel:%28212%29%20431-2864

> [5] mailto:james.grimmelmann@nyls.edu
> [6] mailto:james.grimmelmann@nyls.edu
> [7] http://james.grimmelmann.net

> [8] mailto:gelman@blurryedge.com
> [9] mailto:gelman@blurryedge.com
> [10] http://roundcube.xs4all.nl/tel:415-627-8512

> [11] mailto:ed@felten.com
> [12] mailto:ed@felten.com
> [13] mailto:public-tracking@w3.org
> [14] mailto:public-tracking@w3.org
> [15] mailto:public-tracking@w3.org
> [16] mailto:public-tracking@w3.org

Received on Friday, 21 September 2012 22:32:33 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 17:39:00 UTC