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Additional documentation for Issue-231

From: Jack Hobaugh <jack@networkadvertising.org>
Date: Wed, 16 Oct 2013 20:54:07 -0400
Message-ID: <CAB9xRFkCLifKoXsrApju2aDF3AfGNPz_T9OE1P7m7W_zoHhALA@mail.gmail.com>
To: "public-tracking@w3.org (public-tracking@w3.org)" <public-tracking@w3.org>
Cc: Nicholas Doty <npdoty@w3.org>, Jack Hobaugh <jack@networkadvertising.org>

*2.8 De-identified*


For the purpose of this specification, *tracking data* may be de-identified
using one of two methods:

1.     Expert Review
A qualified statistical or scientific expert concludes, through the use of
accepted analytic techniques, that the risk the information could be used
alone, or in combination with other reasonably available information, to
identify a *user* is very small.

 2.     Safe Harbor
Removal of the following fields and/or data types from the *tracking data*:

 a)     Cleanse URLs to remove end user information such as names, IDs, or
account specific information

b)     Any geographic information that represents a granularity less than
zip code

c)     Date information specific to the end user (e.g. DOB, graduation,
anniversary, etc.)  Transaction dates (purchases, registration, shipping,
etc.) specific to the end user can be retained as long as timestamp
information is removed or obfuscated

d)     User age – note that age group information (e.g. 30-40) can be kept
so long as the ages are expanded to year of birth at a minimum.  Multiple
year age bands are preferred.

e)     Direct contact elements such as telephone numbers, email addresses,
social network usernames, or other public “handles” that uniquely identify
a user on a given service

f)      Social security numbers or other government issued identifiers
(e.g. driver’s license number, registration numbers, tax id numbers,
license plate information)

g)     Account numbers, membership numbers, or other static identifiers
that can be used to identify the user on another site or service or to a
place of business or other organization

h)     Full IP addresses and/or remote hostnames – may be converted to
representative geolocation (no more granular than zip code)

i)      Biometric information, including video or images of the end user,
voice prints/audio recording information

In addition to the removal of the above information, the de-identifying
entity must not have actual knowledge that the remaining information could
be used alone or in combination with other reasonably available information
to identify an individual who is subject of the information.

Further, the de-identifying entity must implement:

1.     Technical safeguards that prohibit re-identification of
de-identified data and/or merging of the original tracking data and
de-identified data

2.     Business processes that specifically prohibit re-identification of
de-identified data and/or merging of the original tracking data and
de-identified data

3.     Business processes that prevent inadvertent release of either the
original *tracking data* or de-identified data

4.     Administrative controls that limit access to both the original
tracking data and de-identified data

If third parties will have access to the de-identified data, the
de-identifying entity must have contractual protections in place that
require the third parties (and their agents or affiliates) to:

1.     Appropriately protect the data

2.     Not attempt to re-identify the data

3.     Only use the data for purposes specified by first party

Regardless of the de-identification approach, unique keys can be used to
correlate records within the de-identified dataset, provided the keys do
not exist outside the de-identified dataset and/or have no meaning outside
the de-identified dataset (i.e. no mapping table can exist that links the
original identifiers to the keys in the de-identified dataset.)

A de-identified dataset becomes *irrevocably de-identified* if the
algorithm information used to generate the unique identifiers (e.g.
encryption key(s) or cryptographic hash “salts”) is destroyed after the
data is de-identified.


Request data sent from user agents can contain information that could
potentially be used to identify end users.  Such data *must* be
de-identified prior to being used for purposes not listed under* permitted
uses.  *While data de-identification does *not* guarantee complete
anonymity, it greatly reduces the risk that a given end user can be

Regardless of the method used (Expert Review or Safe Harbor), the
de-identifying entity should document the processes it uses for
de-identification and any instances where it has implemented
de-identification techniques.  The entity should regularly review the
processes and implementation instances to make sure the appropriate methods
are followed.

Both *tracking data* and de-identified data must be appropriately protected
using industry best practices, including:

·       Access by authorized personnel only

·       Rule of Least Privilege

·       Use of secure transfer/access protocols

·       Secure destruction of data once it is no longer needed

The de-identification and cleansing of URL data is particularly important,
since the variety and format of identifying information will vary.
Considerations for cleansing URL information:

·       Truncation to URL domain only where possible

·       Where path and querystring information must be retained, key-value
information should be scrubbed for known (proprietary) data types as well
as data that matches patterns for known PII formats (e.g. telephone
numbers, email addresses, etc.)


De-identification obligations under DNT closely follow those defined under
the HIPAA Privacy
HIPAA de-identification practices (specified in the Privacy Rule) have been
successfully used by companies to protect Personal Health Information in a
variety of scenarios, including research, confidential sharing, and public

*Jack L. Hobaugh Jr
*Network Advertising Initiative | Counsel & Senior Director of Technology
1634 Eye St. NW, Suite 750 Washington, DC 20006
P: 202-347-5341 | jack@networkadvertising.org
Received on Thursday, 17 October 2013 00:54:36 UTC

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