P3P - Purpose

Purpose

As the World Wide Web became a genuine medium in which to sell products and services, electronic commerce websites tried to collect more information about the people who purchased their merchandise. Some companies used controversial practices such as tracker cookies to ascertain the users' demographic information and buying habits, using this information to provide specifically targeted advertisements. Users who saw this as an invasion of privacy would sometimes turn off HTTP cookies or use proxy servers to keep their personal information secure. P3P is designed to give users a more precise control of the kind of information that they allow to release. According to the W3C the main goal of P3P “is to increase user trust and confidence in the Web through technical empowerment.”

P3P is a machine-readable language that helps to express a website’s data management practices. P3P manages information through privacy policies. When a website uses P3P, they set up a set of policies that allows them to state their intended uses of personal information that may be gathered from their site visitors. When a user decides to use P3P, they set their own set of policies and state what personal information they will allow to be seen by the sites that they visit. Then when a user visits a site, P3P will compare what personal information the user is willing to release, and what information the server wants to get – if the two do not match, P3P will inform the user and ask if he/she is willing to proceed to the site, and risk giving up more personal information. As an example, a user may store in the browser preferences that information about their browsing habits should not be collected. If the policy of a Website states that a cookie is used for this purpose, the browser automatically rejects the cookie. The main content of a privacy policy is the following:

  • which information the server stores:
    • which kind of information is collected (identifying or not);
    • which particular information is collected (IP address, email address, name, etc.);
  • use of the collected information:
    • how this information is used (for regular navigation, tracking, personalization, telemarketing, etc.);
    • who will receive this information (only the current company, third party, etc.);
  • permanence and visibility:
    • how long information is stored;
    • whether and how the user can access the stored information (read-only, optin, optout).

The privacy policy can be retrieved as an XML file or can be included, in compact form, in the HTTP header. The location of the XML policy file that applies to a given document can be:

  1. specified in the HTTP header of the document
  2. specified in the HTML head of the document
  3. if none of the above is specified, the well-known location /w3c/p3p.xml is used (for a similar location compare /favicon.ico)

P3P allows to specify a max-age for caching. A dummy /w3c/p3p.xml file could use this feature:

Read more about this topic:  P3P

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