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Privacy-Preserving Transparency-Enhancing Tools
Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.ORCID iD: 0000-0001-6459-8409
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Transparency is a key principle in democratic societies. For example, the public sector is in part kept honest and fair with the help of transparency through different freedom of information (FOI) legislations. In the last decades, while FOI legislations have been adopted by more and more countries worldwide, we have entered the information age enabled by the rapid development of information technology. This has led to the need for technological solutions that enhance transparency, for example to ensure that FOI legislation can be adhered to in the digital world. These solutions are called transparency-enhancing tools (TETs), and consist of both technological and legal tools. TETs, and transparency in general, can be in conflict with the privacy principle of data minimisation.

The goal of transparency is to make information available, while the goal of data minimisation is to minimise the amount of available information. This thesis presents two privacy-preserving TETs: one cryptographic system forenabling transparency logging, and one cryptographic scheme for storing the data for the so called Data Track tool at a cloud provider. The goal of the transparency logging TET is to make data processing by data controllers transparent to the user whose data is being processed. Our work ensures that the process in which the data processing is logged does not leak sensitive information about the user, and thatthe user can anonymously read the information logged on their behalf. The goal of the Data Track is to make it transparent to users which data controllers they have disclosed data to under which conditions. Furthermore, the Data Track intends to empower users to exercise their rights, online and potentially anonymously, with regard to their disclosed data at the recipient data controllers. Our work ensures that the data kept by the Data Track can be stored at acloud storage provider, enabling easy synchronisation across multiple devices, while preserving the privacy of users by making their storage anonymous toward the provider and by enabling users to hold the provider accountable for the data it stores.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2012. , 22 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2012:57
National Category
Computer Science
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-15685ISBN: 978-91-7063-469-7 (print)OAI: oai:DiVA.org:kau-15685DiVA: diva2:570706
Presentation
2013-01-08, 21A342, Karlstad Universitet, Karlstad, 09:15 (English)
Opponent
Supervisors
Available from: 2012-12-17 Created: 2012-11-20 Last updated: 2017-12-06Bibliographically approved
List of papers
1. Distributed Privacy-Preserving Log Trails
Open this publication in new window or tab >>Distributed Privacy-Preserving Log Trails
2012 (English)Report (Other academic)
Abstract [en]

In the online world, increasing amounts of personal data of users are processed by service providers and other third party data processors. The privacy principle of transparency means that users should be informed about what data about them are processed by whom and how. This report describes a log service that enables users to reconstruct a log trail of these actions, by retrieving log entries from log servers. The information that links log entries into a trail is logged — together with the encrypted action data — to dedicated log servers by the data processors. In the proposed service, log entries of one trail can be spread over different log servers, possibly generated by different data processors. The fact that certain information is logged about a user can already leak information, and adding linking information only elevates this privacy risk. Encrypting the logged information does not suffice to protect against this. In our system, linking information across log databases is cryptographically protected and is only meaningful to the user to whom the log entries relate. In the report, we also consider the fact that log servers and data processors can become compromised. The scheme is therefore auditable, meaning that a third party can validate that log servers cannot make any changes to log entries without being detected, even when they collude with other log servers or data processors.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2012. 147 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2012:24
National Category
Computer Science
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-13309 (URN)978-91-7063-428-4 (ISBN)
Projects
EU/FP7 PrimeLifeIBBT/Index
Funder
EU, FP7, Seventh Framework Programme, 216483
Available from: 2012-05-10 Created: 2012-05-10 Last updated: 2017-12-06Bibliographically approved
2. Unlinking Database Entries: Implementation Issues in Privacy Preserving Secure Logging
Open this publication in new window or tab >>Unlinking Database Entries: Implementation Issues in Privacy Preserving Secure Logging
2010 (English)Conference paper, Published paper (Refereed)
Abstract [en]

This paper discusses implementation issues related to using relational databases as storage when implementing privacy preserving secure logs. In these types of logs it is important to keep the unlinkability properties of log entries intact when the entries are stored. We briefly describe the concept of privacy preserving secure logging and give the rational for it. The problems of using relational database systems as storage is discussed and we suggest three solutions to the problem. Two of the solutions are analyzed and compared and we show that at least one of the solutions is feasible in a real live setting and that the added overhead of the solution is very small.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2010
Keyword
privacy, privacy preserving secure logging, transparency, unlinkability, Ambient intelligence, Computer science, Data privacy, Identity management systems, Intelligent sensors, Relational databases, Secure storage, Social network services, Warranties, Web and internet services
National Category
Computer Science
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-9987 (URN)10.1109/IWSCN.2010.5497998 (DOI)978-1-4244-6939-0 (online) 978-1-4244-6938-3 (print) (ISBN)
Conference
Post Proceedings of 2nd International Workshop on Security and Communication Networks (to appear)
Projects
PrimeLife
Available from: 2012-02-08 Created: 2012-02-08 Last updated: 2017-12-06Bibliographically approved
3. (More) Side Channels in Cloud Storage: Linking Data to Users
Open this publication in new window or tab >>(More) Side Channels in Cloud Storage: Linking Data to Users
2012 (English)In: Privacy and Identity Management for Life: 7th IFIP WG 9.2, 9.6/11.7, 11.4, 11.6/PrimeLife International Summer School, Trento, Italy, September 5-9, 2011, Revised Selected Papers, Berlin, Heidelberg: Springer Berlin/Heidelberg, 2012, 102-115 p.Conference paper, Published paper (Refereed)
Abstract [en]

Public cloud storage services are gaining in popularity and several commercial actors are offering their services for users, however, not always with the security and privacy of their users as the primary design goal. This paper investigates side channels in public cloud storage services that allow the service provider, and in some cases users of the same service, to learn who has stored a given file and to profile users’ usage of the service. These side channels are present in several public cloud storage services that are marketed as secure and privacy-friendly. Our conclusions are that cross-user deduplication should be disabled by default and that public cloud storage services need to be designed to provide unlinkability of users and data, even if the data is encrypted by users before storing it in the cloud.

Place, publisher, year, edition, pages
Berlin, Heidelberg: Springer Berlin/Heidelberg, 2012
Series
IFIP Advances in Information and Communication Technology, ISSN 1868-4238 ; 375
National Category
Computer Science
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-15679 (URN)10.1007/978-3-642-31668-5_8 (DOI)978-3-642-31667-8 (Print) 978-3-642-31668-5 (Online) (ISBN)
Conference
7th IFIP WG 9.2, 9.6/11.7, 11.4, 11.6/PrimeLife International Summer School, Trento, Italy, September 5-9, 2011
Available from: 2012-11-20 Created: 2012-11-20 Last updated: 2017-12-06Bibliographically approved
4. Privacy-Friendly Cloud Storage for the Data Track: An Educational Transparency Tool
Open this publication in new window or tab >>Privacy-Friendly Cloud Storage for the Data Track: An Educational Transparency Tool
2012 (English)In: Secure IT Systems: 17th Nordic Conference, NordSec 2012, Karlskrona, Sweden, October/November 2012, Proceedings / [ed] Audun Jøsang, Bengt Carlsson, Berlin/Heidelberg: Springer Berlin/Heidelberg, 2012, 231-246 p.Conference paper, Published paper (Refereed)
Abstract [en]

The Data Track is a transparency-enhancing tool that aims to educate users by providing them with an overview of all their data disclosures. In this paper, we describe a cryptographic scheme for storing all data disclosures tracked by the Data Track centrally in the cloud in a privacy-friendly way. Our scheme allows users to store their data anonymously, while keeping the cloud provider accountable with regard to the integrity of the data. Furthermore, we introduce a separation of concerns for the different components of the Data Track, well suited for tracking data disclosures from semi-trusted devices that may become compromised. We provide an informal evaluation of our scheme and briefly describe a proof of concept implementation.

Place, publisher, year, edition, pages
Berlin/Heidelberg: Springer Berlin/Heidelberg, 2012
Series
Lecture Notes in Computer Science, ISSN 0302-9743 ; 7617
National Category
Computer Science
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-15680 (URN)10.1007/978-3-642-34210-3 (DOI)978-3-642-34209-7 (Print) 978-3-642-34210-3 (Online) (ISBN)
Conference
17th Nordic Conference, NordSec 2012, Karlskrona, Sweden, October/November 2012
Available from: 2012-11-20 Created: 2012-11-20 Last updated: 2017-12-06Bibliographically approved

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