Roger Clarke's Web-Site

© Xamax Consultancy Pty Ltd,  1995-2024
Photo of Roger Clarke

Roger Clarke's 'P3P Re-visited'

P3P Re-visited

Roger Clarke

Principal, Xamax Consultancy Pty Ltd, Canberra

Visiting Fellow, Department of Computer Science, Australian National University

Version of 20 March 2001

This document was prepared for publication in Privacy Law & Policy Reporter 7, 10 (April 2001). The accompanying resource-page provides access to all papers in the series, and to many additional sources of information

This is the third of a family of three papers. The first is an Overview (1998), and the second is a Critique (1998)

© Xamax Consultancy Pty Ltd, 2001

Available under an AEShareNet Free for Education licence

This document is at

This is a column in Roger Clarke's series on Privacy-Invasive and Privacy-Enhancing Technologies. The introductory article for the series appeared in PLPR 7, 9 (March 2001). This column, including hot-links, is available at

The resources page for the series is at


In the introductory paper to this series, I distinguished privacy-invasive technologies (the PITs), and three different categories of privacy-enhancing technologies (PETs). Two of those are savage PETs which deliver anonymity, and gentle PETs which focus on pseudonymity. This first article in the series considers a technology that arguably belongs to the third category of PETs, which I refer to as 'PIT countermeasures'.

The World Wide Web has delivered an explosion in access to information, and in the ability to publish; but it has been perceived by consumer marketers as a further opportunity to apply old-style consumer manipulation techniques that worked well for them in the broadcast / mass marketing era. One important privacy-invasive mechanism on the web is the capture of personal data through web-forms, cookies and other devices, without consent, or with considerably less than informed consent. This paper examines a proposed enhancement to web-protocols that was originally intended to provide controls over those incursions into privacy.


The World Wide Web Consortium (W3C) is an association of large corporations that fund an organisation directed by the web's inventor, Tim Berners-Lee, to refine existing protocols and develop new ones. The Platform for Privacy Preferences (P3P) is an initiative of a W3C Working Group that is claimed to provide "a simple, automated way for users to gain more control over the use of personal information on Web sites they visit".

Readers of this journal were provided with one of the first published overviews of P3P. See PLPR 5, 2 (July 1998) at 35-39. I followed that with a critique in PLPR 5, 3 (August 1998) at 46-48.

In the earlier of those papers, I depicted the purpose of the P3P specification as being "to enable:

I was positive about P3P's prospects. I based that judgement on the belief that P3P-compliance was to be embedded within web-browsers and web-servers, in order to establish the following process:

The scheme was intended to achieve what W3C referred to as 'informed consent through user choice'. The W3C P3P Working Group maintains a substantial list of papers dealing with P3P, including (to their credit) the criticisms as well as the more positive reviews.

The Gathering Clouds

Privacy advocates adopted varying interpretations of P3P. Several activists, myself included, participated in the W3C Working Group, in the belief that the initiative was capable for delivering real technological protections for web-users. Several others were more sceptical, and preferred to stay outside the Working Group.

In my critique of early 1998, I identified four aspects of P3P that I was concerned about:

At the international privacy conference in Montreal in September 1997, EPIC's Marc Rotenberg presented a classification scheme for technologies:

  1. Technologies of Surveillance (equivalent to my 'PITs');
  2. Technologies for Contracting (including P3P, which he saw as being neutral rather than a positive contribution to privacy);
  3. Technologies for Labelling and Notice (such as 'trust labels'); and
  4. Privacy-Enhancing Technologies (PETs).

To address some of his concerns about the limited contribution that he saw P3P as making, I suggested that some refinements were needed, including:

New York-based Australian, Jason Catlett, of Junkbusters Inc., expressed more serious concerns in an open letter to P3P's designers in September 1999. He depicted P3P as being part of the direct marketing lobby's manoeuvres to convert privacy from the fundamental human right that it is, to nothing more than a consumer preference. It diverted attention away from what is really needed (privacy-protective law complete with enforcement and redress), towards the U.S. corporate view of privacy as merely notice of practices and consumer choice. Rather than a Platform for Privacy Preferences, he saw it as a Pretext for Privacy Procrastination.

P3P as a Pseudo-PET

I've had little to do with P3P during the 18 months since Jason's open letter. I re-visited P3P recently, and was very disappointed with what I found.

The descriptions of the now all-but finalised specification make clear that the protocol specifies only the statement of a web-site's use and disclosure policy. Worse, it is actually depicted as thought it were a push-mechanism, rather than a communication initiated by a request by a browser. The accompanying diagrams even go so far as to imply that the browser submits personal data to the server irrespective of what the web-site's policy statement is.

Critically, the specification contains no minimum requirements of web-browsers. This had to be omitted in order to avoid constraining competition among browser-providers. P3P therefore fails to create any momentum towards the inclusion of the necessary privacy-sensitive features in the tools that users have at their disposal.


The original promise of P3P has been neutered. The judgements of Marc Rotenberg in 1997 and Jason Catlett in 1998, as updated in EPIC (2000), are fully vindicated. P3P is nothing more than a 'privacy policy declaration' standard. That's a mere fraction of what it was meant to be, and of what the situation demands.

The key proponents of the P3P protocol have laboured long and hard in an endeavour to deliver a PET, but the interests of W3C's members have resulted in it being watered down to a mere pseudo-protection.

Key References

Catlett J. (1999) 'Open Letter 9/13 to P3P Developers', September 1999, at

Clarke R. (1998a) 'Platform for Privacy Preferences: An Overview' (April 1998), Privacy Law & Policy Reporter 5, 2 (July 1998) 35-39, at

Clarke R. (1998b) 'Platform for Privacy Preferences: A Critique' (April 1998), Privacy Law & Policy Reporter 5, 3 (August 1998) 46-48, at

EPIC (2000) 'Pretty Poor Privacy: An Assessment of P3P and Internet Privacy' Electronic Privacy Information Center and Junkbusters, June 2000, at

W3C (1998-) 'Platform for Privacy Preferences', World Wide Web Consortium, at Platform for Privacy Preferences (P3P)


This series is supplemented by a resource-page that will be maintained on an ongoing basis. PLPR readers are invited, and actively encouraged, to contribute sources and suggestions for enhancement to, and to bookmark the page for their own use and for communication to others.

xamaxsmall.gif missing
The content and infrastructure for these community service pages are provided by Roger Clarke through his consultancy company, Xamax.

From the site's beginnings in August 1994 until February 2009, the infrastructure was provided by the Australian National University. During that time, the site accumulated close to 30 million hits. It passed 65 million in early 2021.

Sponsored by the Gallery, Bunhybee Grasslands, the extended Clarke Family, Knights of the Spatchcock and their drummer
Xamax Consultancy Pty Ltd
ACN: 002 360 456
78 Sidaway St, Chapman ACT 2611 AUSTRALIA
Tel: +61 2 6288 6916

Created: 18 February 2001 - Last Amended: 20 March 2001; addition of FfE licence 5 March 2004 by Roger Clarke - Site Last Verified: 15 February 2009
This document is at
Mail to Webmaster   -    © Xamax Consultancy Pty Ltd, 1995-2022   -    Privacy Policy