Privacy‐enhancing technologies

Privacy enhancing technologies (PET) is a general term for a set of computer tools, applications and mechanisms which &mdash; when integrated in online services or applications, or when used in conjunction with such services or applications &mdash; allow online users to protect the privacy of their personally identifiable information (PII) provided to and handled by such services or applications.

Privacy enhancing technologies can also be defined as:

"Privacy-Enhancing Technologies is a system of ICT measures protecting informational privacy by eliminating or minimising personal data thereby preventing unnecessary or unwanted processing of personal data, without the loss of the functionality of the information system."

Goals of PETs
PETs aim at allowing users to take one or more of the following actions related to their personal data sent to, and used by, online service providers, merchants or other users:


 * increase control over their personal data sent to, and used by, online service providers and merchants (or other online users) (self-determination)
 * data minimization: minimize the personal data collected and used by service providers and merchants
 * choose the degree of anonymity (e.g., by using pseudonyms, anonymizers or anonymous data credentials)
 * choose the degree of unlinkability (e.g., by using multiple virtual identities)
 * achieve informed consent about giving personal data to online service providers and merchants
 * provide the possibility to negotiate the terms and conditions of giving personal data to online service providers and merchants (data handling/privacy policy negotiation). In privacy negotiations, consumers and service providers establish, maintain, and refine privacy policies as individualized agreements through the ongoing choice amongst service alternatives. In incentivized privacy negotiations, the transaction partners may additionally bundle the personal information collection and processing schemes with monetary or non-monetary rewards.
 * provide the possibility to have these negotiated terms and conditions technically enforced by the infrastructures of online service providers and merchants (i.e., not just having to rely on promises, but being confident that it is technically impossible for service providers to violate the agreed upon data handling conditions)
 * provide the possibility to remotely audit the enforcement of these terms and conditions at the online service providers and merchants (assurance)
 * data tracking: allow users to log, archive and look up past transfers of their personal data, including what data has been transferred, when, to whom and under what conditions
 * facilitate the use of their legal rights of data inspection, correction and deletion.

Existing PETs
Examples of existing privacy enhancing technologies are:


 * Communication anonymizers hiding the real online identity (email address, IP address, etc.) and replacing it with a non-traceable identity (disposable/one-time email address, random IP address of hosts participating in an anonymizing network, pseudonym, etc.). They can be applied to email, Web browsing, P2P networking, VoIP, chat, instant messaging, etc.
 * Shared bogus online accounts. One person creates an account for MSN, providing bogus data for name, address, phone number, preferences, life situation etc. They then publish their user-ID and password on the Internet. Everybody can now use this account comfortably. Thereby the user is sure that there is no personal data about him in the account profile. (Moreover, he is freed from the hassle of having to register at the site himself.)
 * Access to personal data: The service provider's infrastructure allows users to inspect, correct or delete all their data stored at the service provider.

Future PETs
Examples of privacy enhancing technologies that are being researched or developed are:
 * Wallets of multiple virtual identities; ideally unlinkable. Such wallets allow the efficient and easy creation, management and usage of virtual identities.
 * Anonymous credentials: asserted properties/attributes or rights of the holder of the credential that don't reveal the real identity of the holder and that only reveal so much information as the holder of the credential is willing to disclose. The assertion can be issued by the user herself, by the provider of the online service or by a third party (another service provider, a government agency, etc.). For example:
 * Online car rental. The car rental agency doesn't really need to know the true identity of the customer. It only needs to make sure that the customer is over 23 (as an example), that the customer has a driving licence, that the customer has health insurance for accidents (as an example), and that the customer is paying. Thus no real need to know her real name nor her address nor any other personal information. Anonymous credentials allow both parties to be comfortable: they allow the customer to only reveal so much data which the car rental agency needs for providing its service (data minimisation), and they allow the car rental agency to verify their requirements and get their money. When ordering a car online, the user, instead of providing the classical name, address and credit card number, provides the following credentials, all issued to pseudonyms, i.e. not to the real name of the customer:
 * An assertion of minimal age, issued by the state, proving that the holder is older than 23 (i.e. the actual age is not provided)
 * A driving licence, i.e. an assertion, issued by the motor vehicle control agency, that the holder is entitled to drive cars
 * A proof of insurance, issued by the health insurance
 * Digital cash
 * With this data, the car rental agency is in possession of all the data it needs to rent the car, it can thus, as an example, provide the unlocking code to the customer with which she can unlock the closet where the car key is kept.
 * Similar scenarios are buying wine at an Internet wine store or renting a movie at an online movie rental store.


 * Negotiation and enforcement of data handling conditions. Before ordering a product or service online, the user and the online service provider or merchant negotiate the type of personal data that is to be transferred to the service provider. This includes the conditions that shall apply to the handling of the personal data, such as whether or not it may be sent to third parties (profile selling) and under what conditions (e.g. only while informing the user), or at what time in the future it shall be deleted (if at all). As an example, it can be negotiated that personal data mustn't be handed out to third parties or that the data is to be deleted after 3 months following the end of the contract. While this negotiation takes place, the online service provider communicates his requirements about the minimum amount of data he needs to provide the wanted service. Additional personal data may be asked for, too, but will be clearly labelled as optional. After the transfer of personal data took place, the agreed upon data handling conditions are technically enforced by the infrastructure of the service provider, which is capable of managing and processing and data handling obligations. Moreover, this enforcement can be remotely audited by the user, for example by verifying chains of certification based on Trusted computing modules or by verifying privacy seals/labels that were issued by third party auditing organisations (e.g. data protection agencies). Thus instead of the user having to rely on the mere promises of service providers not to abuse personal data, users will be more confident about the service provider adhering to the negotiated data handling conditions.


 * Data transaction log. Users can log what personal data they sent to which service provider, when and under what conditions. These logs are stored and allow users to determine what data they have sent to whom, or they can establish the type of data that is in possession by a specific service provider. This leads to more transparency, which is a prerequisite of being in control.