=Paper=
{{Paper
|id=Vol-3674/ASPIRING-paper1
|storemode=property
|title=Towards a Decentralized Data Privacy Protocol for Self-Sovereignty in the Digital World
|pdfUrl=https://ceur-ws.org/Vol-3674/ASPIRING-paper1.pdf
|volume=Vol-3674
|authors=Rodrigo Falcão,Arghavan Hosseinzadeh
|dblpUrl=https://dblp.org/rec/conf/rcis/FalcaoH24
}}
==Towards a Decentralized Data Privacy Protocol for Self-Sovereignty in the Digital World==
https://ceur-ws.org/Vol-3674/ASPIRING-paper1.pdf
Towards a Decentralized Data Privacy Protocol for
Self-sovereignty in the Digital World
Rodrigo Falcão1,∗ , Arghavan Hosseinzadeh1
1
Fraunhofer IESE, Fraunhofer-Platz 1, 67663 Kaiserslautern, Germany
Abstract
A typical user interacts with many digital services nowadays, providing these services with their data.
As of now, the management of privacy preferences is service-centric: Users must manage their privacy
preferences according to the rules of each service provider, meaning that every provider offers its unique
mechanisms for users to control their privacy settings. However, managing privacy preferences holisti-
cally (i.e., across multiple digital services) is just impractical. In this vision paper, we propose a paradigm
shift towards an enriched user-centric approach for cross-service privacy preferences management: the
realization of a decentralized data privacy protocol.
Keywords
personal data, privacy, protocol
1. Motivation
Not long ago, users navigated through Internet-based services (e.g., websites) leaving behind an
unnoticed trail of personal data, browsing habits, and online interactions. Tracking technologies
such as cookies, the development of data analysis techniques, and the rise of tech giants
such as Google and Facebook (whose online presence became pervasive) have given rise to a
massive concentration of data, which has supported targeted advertising for diverse purposes,
sometimes raising ethical concerns [1]. These concerns led to the emergence of several data
protection initiatives around the globe, resulting in regulations such as the GDPR [2] and the
Data Governance Act [3], which aim to facilitate data exchange while increasing trust and
ensuring data protection. One of the most tangible consequences a user experiences occurs
when they visit a website using cookie technology: On the first access, they are asked to accept
or reject cookies.
While users have been given some sort of freedom to choose which types of data are used by
different services and for what purposes, and have also been entitled to change their preferences
and revoke permissions for data usage, it is still hard for them maintain sovereignty over their
choices. Gradually, their data and their choices regarding data usage are spread across the
dozens, hundreds, or even thousands of digital services they interact with. In the long run, it is
easy to lose track of where data is stored and used, by whom, and for what purpose. Taking
Joint Proceedings of RCIS 2024 Workshops and Research Projects Track, May 14-17, 2024, Guimarães, Portugal
∗
Corresponding author.
Envelope-Open rodrigo.falcao@iese.fraunhofer.de (R. Falcão); arghavan.hosseinzadeh@iese.fraunhofer.de (A. Hosseinzadeh)
GLOBE http://rodrigofalcao.info/ (R. Falcão)
Orcid 0000-0003-1222-0046 (R. Falcão); 0009-0001-8699-9972 (A. Hosseinzadeh)
© 2024 Copyright for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
CEUR
ceur-ws.org
Workshop ISSN 1613-0073
Proceedings
back control of the usage of their data becomes a near-impossible endeavor. Even if each digital
service were shipped with a comprehensive and easy-to-use privacy preferences management
tool, users would still have to remember all the services that use their data, visit them, and, one
after another, review their privacy preferences if they want to. In other words, from the end
user’s perspective, privacy preferences management solutions are distributed across virtually
all digital services they interact with. For this very reason, they cannot be effective. To make
matters worse, there is a lack of standardization in the field.
In this vision paper, we propose a paradigm shift in how we approach the issue of privacy
preferences management. The current paradigm focuses on the interaction between a user and
a digital service. It encompasses usable privacy management tools, which are a necessary but
insufficient solution. We envision a future where a fully user-centric approach takes a holistic
view of all digital services, allowing users to manage their preferences in one place, without
any particular service provider monopolizing this space. This is where the decentralized data
privacy protocol comes into play. It can be implemented by any party and offers benefits to
both end users and service providers. It also opens up opportunities for the development of
new privacy-enhancing technologies on top of it. The remainder of this paper is structured as
follows: In Section 2, we review recent related work; Section 3 outlines the protocol concept;
Section 4 explores the benefits and opportunities; and Section 5 concludes the paper, outlining
our next steps.
2. Related work
Several years prior, the World Wide Web Consortium (W3C) developed the Platform for Privacy
Preferences (P3P) to enable web browsers to automatically read, interpret, and compare website
privacy policies against user preferences or settings [4]. Despite its initial innovation, few
websites have adopted P3P, and growing privacy needs have surpassed the protocol’s capabilities.
The most recent advancements in research with respect to preserving user privacy focus
on privacy policy languages and user-friendly settings for privacy preferences. Gharib [5]
argues that most data subjects blindly accept the notices, not because they do not value their
privacy, but because most privacy policies and terms of services are long, complex, and hard
to understand, so the author introduces a model for informed consent. The model involves a
Matching Component that compares the privacy preferences of the user that is included within
their Personal Privacy Profile (PPPo) and the privacy policies that are published by the service
providers and automates the process of giving consent. A dynamic contextual notice is provided
to the user when the user preferences and the policies do not match. Accordingly, the user can
make an informed decision concerning the consent request. Gharib also proposes an ontology
that can be used for realizing preferences and policies. However, where to store the PPPos
seems to be out of the scope of this work.
Dehling et al. [6] introduce Privacy Cockpits, which are central dashboards for users to
navigate and manage their personal data. This solution aims to ease the enforcement of
regulations such as GDPR, although it focuses on protecting the data used across various
services within specific digital ecosystems.
In 2020, the European Data Protection Supervisor introduced the Personal Information
Management Systems (PIMS) concept [7]. The PIMS concept offers a new approach in which
individuals are the “holders” of their own personal information. PIMS aims to empower users
to take charge of their digital identity and the use of their personal information across various
services and platforms. In recent years, several initiatives and projects have claimed PIMS
features. Among these, the Solid protocol [8] stands out. It proposes a set of conventions and
tools for building a decentralized platform for social Web applications. In order to address the
challenge of obtaining consent for processing personal data, Florea and Esteves [9] introduced a
policy layer into the Solid ecosystem. They integrated the usage of the ODRL Policy Language
[10], the ODRL profile for Access Control (OAC) [11], and the Data Privacy Vocabulary (DPV)
[12] to allow Solid users to express their privacy preferences. By integrating such a policy layer
into the Solid ecosystem, the matching process regarding users’ preferences and requests for
data can be automated. However, the focus of the Solid protocol remains on data management
mechanisms that allow users to store their data such as contacts and photos in Personal Online
Datastores (PODs) and control access of applications to this data. We therefore still see an
ongoing need for a protocol specifically designed for privacy preferences management.
3. A paradigm shift
We propose a paradigm shift by adjusting the context of the problem. Users need adequate
means to exercise their data sovereignty. Tools can implement diverse models to provide such
means; however, regardless of whether we consider the implementation of the “notice and
consent model”, the “informed consent model”, or “data protection cockpits”, to name but a few
strategies, solutions address the data sovereignty challenge in the context of the interaction
between the user and a given digital service (or ecosystem). Consider now the exercise of data
sovereignty in the context of not only one digital service, but all of them. If we have this goal
in mind, current strategies – though valuable and necessary – fall short. It is not enough that
each digital service provides its own means for users to manage their preferences; instead, each
individual should be able to manage their data preferences across all digital services that use
their data. A new centralized digital service could fill this gap; however, to be effective, it would
require the providers of digital services to adhere to it, and users would still have to rely on a
centralized service offered by yet another service provider.
Due to these reasons, we argue that a more adequate solution should be positioned at a higher
level of abstraction and be developed as an open protocol that anyone can implement. We
envision a decentralized protocol for users and services to manage data privacy preferences. A
protocol can be defined as a set of syntactic and semantic rules that standardize communication
between two or more entities. Using a defined protocol, users could tell the digital services where
they want to store and manage their privacy preferences. We call this place the user’s Personal
Privacy Preferences Place (P4). P4 instances could be hosted by a user’s trusted third-party or
even be self-hosted. For example, Figure 1 illustrates a scenario where two users, Alice and
Bob, use different sets of digital services. Alice manages her privacy preferences through a P4
instance hosted and operated by a trusted company, while Bob manages his using a self-hosted
P4 instance. The digital services can interoperate with both P4 instances because the digital
services and the P4 instances implement their roles in the protocol.
Trusted third-party Another P4 instance
company P4 instance ddpp (self-hosted by Bob)
realize realize
host P4 role P4 role
and operate
realize realize
data consumer data consumer use,
role role host, and
use operate
Alice use use
Bob
Digital services
Figure 1: Overview of the decentralized data privacy protocol (ddpp).
Shaping the requirements. The goal of the protocol is to improve the usability and self-
sovereignty of privacy preferences from the point of view of end users in the context of numerous
digital services. To achieve this goal, the protocol must fulfill certain quality and functional
requirements. From a quality perspective, the list includes (but is not limited to) openness (the
protocol shall have an open specification in order to enable operational independence, meaning
that anyone could implement its elements), adaptability (The protocol should not prevent
providers from setting their privacy preferences freely, i.e., they shouldn’t be required to change
the way they define privacy preferences), and confidentiality (the personal privacy preferences
place shall not store nor exchange private user data, but only users’ privacy preferences data).
Concerning the functional aspects, we highlight three fundamental constructs: the data structure
(the protocol shall specify a privacy preferences meta-model whose instances express privacy
preferences using generic elements), the behavior (the protocol shall specify the interaction
flows between the participants, namely the user, their P4, and the digital service), and the
interfaces (syntactic and semantic description of each interface that the participating systems
must implement to enable the desired behavior).
On the interaction flows. The protocol must support at least two key flows: handshake
and update. Using the handshake flow, the user informs their digital service about their P4
instance. After the user sets their initial privacy preferences and after the authorization process,
the digital service can communicate with the user’s P4 instance to exchange privacy preferences
data. Using the update flow, every change that the user makes in the privacy preferences on
their P4 should be reflected in the affected digital services, and every change made in a digital
service should be reflected in the user’s P4.
4. Benefits and opportunities
The envisioned approach is an additional step towards enabling data sovereignty as the imple-
mentation of the protocol takes the exclusive control of privacy management means from the
service providers and gives it to the actual data subjects, i.e., the users. Also, following the same
specification language and a standard ontology can facilitate the matching process between
privacy policies and user’s preferences and further automate it
From the point of view of the service provider, and given that we are living in a regulated
society concerning data privacy, non-compliance poses a significant financial risk due to security,
safety, and trust issues. Therefore, adherence to an open standard would help service providers
transfer at least part of the risk beyond the boundaries of their companies. Furthermore,
adopting an open privacy management standard would increase transparency and help build
trust in the service providers.
This idea can be boosted by the adoption of self-sovereign identities (SSI), which have gained
increasing traction through initiatives such as the eIDAS regulation [13]. The location of the
user’s privacy preferences could be tied to their identities. When a user provides their identity
to an arbitrary digital service, the service can directly read the user’s privacy preferences from
the P4 instance.
Customized and optimized P4 instances can give users extended privacy management capa-
bilities in comparison to those offered by their digital services. For example, while a certain
digital service may only allow for either consenting or denying access to certain data for a given
purpose, P4 instances can provide users with the ability to set dynamic rules or constraints on
their preferences (e.g., revoke consent for data X for the purpose Y in all digital services located
in Z 30 days after consent was granted). The development, customization, and operation of P4
instances opens up new business opportunities for companies.
5. Conclusion and outlook
So far, it has been hard for users to maintain sovereignty over their privacy preferences because
privacy preferences management is not centered on the users but scattered across numerous
digital services. In this paper, we sketched our vision of a decentralized data privacy protocol.
We acknowledge that the vision does not provide details, which can make a difference in
realizing a robust protocol. The challenges to overcome will become more evident as the details
are added.
The implementation of this protocol will allow users to manage their privacy preferences
effortlessly. It primarily enables communication between web services and P4 instances but is
also available for any digital service to implement and utilize. Research plays a key role in the
fulfillment of this vision. From our point of view, the next steps include a review of extensible
data privacy meta-models, the design of the protocol flow, the design of a reference architecture
for P4, and prototyping of a reference implementation.
Acknowledgments
This work has been funded by the German Federal Ministry of Education and Research (BMBF)
(grant numbers 16KIS1507 and 16KIS1510).
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