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A vast number of online services is based on users contributing their personal information. Examples are manifold, including social networks, electronic commerce, sharing websites, lodging platforms, and genealogy. In all cases user privacy depends on a collective trust upon all involved intermediaries, like service providers, operators, administrators or even help desk staff. A single adversarial party in the whole chain of trust voids user privacy. Even more, the number of intermediaries is ever growing. Thus, user privacy must be preserved at every time and stage, independent of the intrinsic goals any involved party. Furthermore, next to these new services, traditional offline analytic systems are replaced by online services run in large data centers. Centralized processing of electronic medical records, genomic data or other health-related information is anticipated due to advances in medical research, better analytic results based on large amounts of medical information and lowered costs. In these scenarios privacy is of utmost concern due to the large amount of personal information contained within the centralized data. We focus on the challenge of privacy-preserving processing on genomic data, specifically comparing genomic sequences. The problem that arises is how to efficiently compare private sequences of two parties while preserving confidentiality of the compared data. It follows that the privacy of the data owner must be preserved, which means that as little information as possible must be leaked to any party participating in the comparison. Leakage can happen at several points during a comparison. The secured inputs for the comparing party might leak some information about the original input, or the output might leak information about the inputs. In the latter case, results of several comparisons can be combined to infer information about the confidential input of the party under observation. Genomic sequences serve as a use-case, but the proposed solutions are more general and can be applied to the generic field of privacy-preserving comparison of sequences. The solution should be efficient such that performing a comparison yields runtimes linear in the length of the input sequences and thus producing acceptable costs for a typical use-case. To tackle the problem of efficient, privacy-preserving sequence comparisons, we propose a framework consisting of three main parts. a) The basic protocol presents an efficient sequence comparison algorithm, which transforms a sequence into a set representation, allowing to approximate distance measures over input sequences using distance measures over sets. The sets are then represented by an efficient data structure - the Bloom filter -, which allows evaluation of certain set operations without storing the actual elements of the possibly large set. This representation yields low distortion for comparing similar sequences. Operations upon the set representation are carried out using efficient, partially homomorphic cryptographic systems for data confidentiality of the inputs. The output can be adjusted to either return the actual approximated distance or the result of an in-range check of the approximated distance. b) Building upon this efficient basic protocol we introduce the first mechanism to reduce the success of inference attacks by detecting and rejecting similar queries in a privacy-preserving way. This is achieved by generating generalized commitments for inputs. This generalization is done by treating inputs as messages received from a noise channel, upon which error-correction from coding theory is applied. This way similar inputs are defined as inputs having a hamming distance of their generalized inputs below a certain predefined threshold. We present a protocol to perform a zero-knowledge proof to assess if the generalized input is indeed a generalization of the actual input. Furthermore, we generalize a very efficient inference attack on privacy-preserving sequence comparison protocols and use it to evaluate our inference-control mechanism. c) The third part of the framework lightens the computational load of the client taking part in the comparison protocol by presenting a compression mechanism for partially homomorphic cryptographic schemes. It reduces the transmission and storage overhead induced by the semantically secure homomorphic encryption schemes, as well as encryption latency. The compression is achieved by constructing an asymmetric stream cipher such that the generated ciphertext can be converted into a ciphertext of an associated homomorphic encryption scheme without revealing any information about the plaintext. This is the first compression scheme available for partially homomorphic encryption schemes. Compression of ciphertexts of fully homomorphic encryption schemes are several orders of magnitude slower at the conversion from the transmission ciphertext to the homomorphically encrypted ciphertext. Indeed our compression scheme achieves optimal conversion performance. It further allows to generate keystreams offline and thus supports offloading to trusted devices. This way transmission-, storage- and power-efficiency is improved. We give security proofs for all relevant parts of the proposed protocols and algorithms to evaluate their security. A performance evaluation of the core components demonstrates the practicability of our proposed solutions including a theoretical analysis and practical experiments to show the accuracy as well as efficiency of approximations and probabilistic algorithms. Several variations and configurations to detect similar inputs are studied during an in-depth discussion of the inference-control mechanism. A human mitochondrial genome database is used for the practical evaluation to compare genomic sequences and detect similar inputs as described by the use-case. In summary we show that it is indeed possible to construct an efficient and privacy-preserving (genomic) sequences comparison, while being able to control the amount of information that leaves the comparison. To the best of our knowledge we also contribute to the field by proposing the first efficient privacy-preserving inference detection and control mechanism, as well as the first ciphertext compression system for partially homomorphic cryptographic systems.

Nachhaltige und ethisch vertretbare Beschaffung und Produktion gehören zu den großen Herausforderungen, die aus dem rasanten Klimawandel und der wachsenden Weltbevölkerung resultieren. Die Erneuerbare-Energien-Richtlinie II der EU und das deutsche Lieferkettensorgfaltspflichtengesetz sind nur zwei Beispiele für die Vielzahl von Gesetzen und Vorschriften, die Standards für nachhaltige und ethisch vertretbare Beschaffung und Produktion vorgeben. Sie implizieren einen Bedarf an Transparenz, Rückverfolgbarkeit und Verifizierbarkeit von Lieferketten und Transaktionen. Öffentliche Verifikationen von Transaktionen entlang von Lieferketten ermöglichen es Dritten, die Einhaltung von Standards und Richtlinien und den Wahrheitsgehalt von Nachhaltigkeitsversprechen zu überprüfen. Folglich kann die öffentliche Überprüfbarkeit Kunden, öffentlichen Stellen und Nichtregierungsorganisationen dabei helfen, Verstöße und Betrug in Lieferketten aufzudecken. Dies wiederum kann dazu beitragen, den Druck zur Einhaltung geltender Standards und Vorschriften zu erhöhen. Transaktionen in Lieferketten basieren oft auf vertraulichen Informationen, wie beispielsweise Mengen und Preise. Die Transparenz derartiger Daten könnte auf Geschäftsgeheimnisse schließen lassen, was direkten Einfluss auf die Wettbewerbsvorteile der beteiligten Firmen hätte. Die Vereinbarkeit von Transparenz und Vertraulichkeit scheint jedoch auf den ersten Blick widersprüchlich zu sein. Diese Dissertation stellt sich der Herausforderung, die öffentliche Verifizierbarkeit von Transaktionen in Lieferketten unter Wahrung der Vertraulichkeit zu ermöglichen. Ausgehend von zwei Fallbeispielen für Lieferketten-Verifikationen werden zunächst Anforderungen an Lösungen untersucht und fünf Forschungsfragen abgeleitet. Anschließend wird eine universelle Lösung entworfen, welche Transparenz und Vertraulichkeit in Einklang bringt. Das vorgestellte Systemmodell ermöglicht sichere öffentliche Verifikationen durch den Einsatz von Fully Homomorphic Encryption (FHE) und Proxy Re-Encryption (PRE). Um die Eignung des Systemmodells für eine Vielzahl realer Szenarien zu verdeutlichen, werden in dieser Dissertation Protokolle für verschiedene Verifikationsfunktionen entworfen. Dies umfasst die Verifikation von Bilanzen, motiviert durch den Handel mit nachhaltigem Palmöl, sowie die Verifikation von Verhältnissen, veranschaulicht durch die Verarbeitung verschiedener Arten von Kobalt. Durch theoretische und empirische Untersuchungen wird nachgewiesen, dass die Protokolle sichere öffentliche Verifikationen für realitätsnahe Szenarien in praktikabler Zeit ermöglichen. Im Weiteren werden die Sicherheitseigenschaften und -implikationen des vorgeschlagenen Systemmodells und der Protokolle untersucht. Dies beinhaltet eine formale Analyse des Risikos, vertrauliche Informationen im Falle wiederholter, gleicher Verifikationen preiszugeben. Aufgrund der Anfälligkeit gegenüber derartigen Angriffen beim Verwenden probabilistischer Output Obfuscation, wird das Paradigma der Data-Dependent Deterministic Obfuscation (D3O) vorgestellt. D3O ist ein universelles Konzept und damit unabhängig vom Anwendungsfall der Lieferketten-Verifikation. Daher kann es in einer Vielzahl weiterer Protokolle für sichere Berechnungen eingesetzt werden, um das Abfließen vertraulicher Informationen zu reduzieren. / Sustainable and ethical sourcing and production are major challenges that arise from rapid climate change and our growing world population. The EU's Renewable Energy Directive II and the German Supply Chain Act are just two examples of the multitude of laws and regulations that define standards for sustainable and ethical sourcing and production. They imply a need for supply chain transparency, traceability, and verification. Public verification of supply chain transactions gives any third-party verifier the chance to evaluate compliance and the correctness of claims based on supply chain transaction details. Therefore, public verification can help customers, buyers, regulators, and non-governmental organizations uncover non-compliance and fraud committed by supply chain actors. This, in turn, can help increase the pressure to comply with applicable standards and regulations. Supply chain transactions often involve confidential data like amounts or prices. Transparency of such data could leak trade secrets and affect companies' competitive advantages. However, reconciling transparency with confidentiality seems contradictory at first glance. This thesis takes up the challenge of enabling privacy-preserving public verification of confidential supply chain transactions. Given two exemplary real-world use cases for supply chain verification, the thesis first investigates requirements for valid solutions and infers five research questions. It then designs a universal solution that combines transparency with confidentiality. The proposed system model achieves privacy-preserving public verification by employing the cryptographic techniques of fully homomorphic encryption (FHE) and proxy re-encryption (PRE). To demonstrate the suitability of the system model for a large variety of lifelike supply chain verification scenarios, the thesis designs privacy-preserving protocols for different verification functions. This includes the verification of balances, using the trade in sustainable palm oil as an example, as well as the verification of ratios, motivated by different forms of cobalt sourcing. These protocols are evaluated both theoretically and empirically. Through extensive empirical evaluation, the proposed protocols prove to enable privacy-preserving public verification for the mentioned supply chain scenarios in practical time. Additionally, this thesis investigates the security implications of the proposed system model and protocols and formally analyzes the risk of leaking information through repeated similar verifications. Based on the identified vulnerability to such attacks in the case of probabilistically obfuscated protocol outputs, the thesis introduces and investigates the paradigm of data-dependent deterministic obfuscation (D3O). D3O is a universal concept that is independent of the field of supply chain verification. It can reduce the leakage of confidential information in a large class of privacy-preserving protocols.

Die Chemnitzer Linux-Tage fanden am 13. und 14. März 2010 auf dem Campus der Technischen Universität Chemnitz statt. Neben den Präsentationen im Foyer zogen vor allem die Vorträge über 2500 Besucher zur 12. Auflage der Veranstaltung. Der Band vereint den Inhalt von 15 Hauptvorträgen und die Abstrakts von 76 weiteren Beiträgen und stellt damit einen Überblick über das weit gefächerte Programm der Veranstaltung dar. / The Chemnitz Linux Days took place at the campus of the Chemnitz University of Technology. Besides the presentations at the foyer the lectures were first of all attractive for more than 2.500 visitors. This volume contains the content of 15 main lectures and abstracts of 76 further talks and hence gives a survey of the broadly based program of this event.

Nutzerinformationen des Universitätsrechenzentrums

Nutzerinformationen des Universitätsrechenzentrums

Nutzerinformationen des Universitätsrechenzentrums:A Toolbox for System Configuration and Administration (ToSCA) Sicheres Programmieren mit PHP (Teil 3) "Nutzerforum des URZ" - Neue Veranstaltungsreihe IP-Adressvergabe Windows XP Service Pack 2 - Erfahrungen im URZ Adobe-Rahmenvertrag Kurzinformationen Software-News

Nutzerinformationen des Universitätsrechenzentrums:A Toolbox for System Configuration and Administration (ToSCA) Sicheres Programmieren mit PHP (Teil 3) 'Nutzerforum des URZ' - Neue Veranstaltungsreihe IP-Adressvergabe Windows XP Service Pack 2 - Erfahrungen im URZ Adobe-Rahmenvertrag Kurzinformationen Software-News

Die Chemnitzer Linux-Tage fanden am 13. und 14. März 2010 auf dem Campus der Technischen Universität Chemnitz statt. Neben den Präsentationen im Foyer zogen vor allem die Vorträge über 2500 Besucher zur 12. Auflage der Veranstaltung. Der Band vereint den Inhalt von 15 Hauptvorträgen und die Abstrakts von 76 weiteren Beiträgen und stellt damit einen Überblick über das weit gefächerte Programm der Veranstaltung dar. / The Chemnitz Linux Days took place at the campus of the Chemnitz University of Technology. Besides the presentations at the foyer the lectures were first of all attractive for more than 2.500 visitors. This volume contains the content of 15 main lectures and abstracts of 76 further talks and hence gives a survey of the broadly based program of this event.