Pseudonymization and its Application to Cloud-based eHealth Systems

Responding to the security and privacy issues of information systems, we propose a novel pseudonym solution. This pseudonym solution has provable security to protect the identities of users by employing user-generated pseudonyms. It also provides an encryption scheme to protect the security of the users’ data stored in the public network. Moreover, the pseudonym solution also provides the authentication of pseudonyms without disclosing the users’ identity information. Thus the dependences on powerful trusted third parties and on the trustworthiness of system administrators may be appreciably alleviated. Electronic healthcare systems (eHealth systems), as one kind of everyday information system, with the ability to store and share patients’ health data efficiently, have to manage in-formation of an extremely personal nature. As a consequence of known cases of abuse and attacks, the security of the health data and the privacy of patients are a great concern for many people and thus becoming obstacles to the acceptance and spread of eHealth systems. In this thesis, we survey current eHealth systems in both research and practice, analyzing potential threats to the security and privacy. Cloud-based eHealth systems, in particular, enable applications with many new features in data storing and sharing. We analyze the new issues on security and privacy when cloud technology is introduced into eHealth systems. We demonstrate that our proposed pseudonym solution can be successfully applied to cloud-based eHealth systems. Firstly, we utilize the pseudonym scheme and encryption scheme for storing and retrieving the electronic health records (EHR) in the cloud. The identities of patients and the confidentiality of EHR contents are provably guaranteed by advanced cryptographic algorithms. Secondly, we utilize the pseudonym solution to protect the privacy of patients from the health insurance companies. Only necessary information about patients is disclosed to the health insurance companies, without interrupting the cur-rent normal business processes of health insurance. At last, based on the pseudonym solution, we propose a new procedure for the secondary use of the health data. The new procedure protects the privacy of patients properly and enables patients’ full control and clear consent over their health data to be secondarily used. A prototypical application of a cloud-based eHealth system implementing our proposed solution is presented in order to exhibit the practicability of the solution and to provide intuitive experiences. Some performance estimations of the proposed solution based on the implementation are also provided.Um gewisse Sicherheits- und Datenschutzdefizite heutiger Informationssysteme zu beheben, stellen wir eine neuartige Pseudonymisierungslösung vor, die benutzergenerierte Pseudonyme verwendet und die Identitäten der Pseudonyminhaber nachweisbar wirksam schützt. Sie beinhaltet neben der Pseudonymisierung auch ein Verschlüsselungsverfahren für den Schutz der Vertraulichkeit der Benutzerdaten, wenn diese öffentlich gespeichert werden. Weiterhin bietet sie ein Verfahren zur Authentisierung von Pseudonymen, das ohne die Offenbarung von Benutzeridentitäten auskommt. Dadurch können Abhängigkeiten von vertrauenswürdigen dritten Stellen (trusted third parties) oder von vertrauenswürdigen Systemadministratoren deutlich verringert werden. Elektronische Gesundheitssysteme (eHealth-Systeme) sind darauf ausgelegt, Patientendaten effizient zu speichern und bereitzustellen. Solche Daten haben ein extrem hohes Schutzbedürfnis, und bekannte Fälle von Angriffen auf die Vertraulichkeit der Daten durch Privilegienmissbrauch und externe Attacken haben dazu geführt, dass die Sorge um den Schutz von Gesundheitsdaten und Patientenidentitäten zu einem großen Hindernis für die Verbreitung und Akzeptanz von eHealth-Systemen geworden ist. In dieser Dissertation betrachten wir gegenwärtige eHealth-Systeme in Forschung und Praxis hinsichtlich möglicher Bedrohungen für Sicherheit und Vertraulichkeit der gespeicherten Daten. Besondere Beachtung finden cloudbasierte eHealth-Systeme, die Anwendungen mit neuartigen Konzepten zur Datenspeicherung und -bereitstellung ermöglichen. Wir analysieren Sicherheits- und Vertraulichkeitsproblematiken, die sich beim Einsatz von Cloud-Technologie in eHealth-Systemen ergeben. Wir zeigen, dass unsere Pseudonymisierungslösung erfolgreich auf cloudbasierte eHealth-Systeme angewendet werden kann. Dabei werden zunächst das Pseudonymisierungs- und das Verschlüsselungsverfahren bei der Speicherung und beim Abruf von elektronischen Gesundheitsdatensätzen (electronic health records, EHR) in der Cloud eingesetzt. Die Vertraulichkeit von Patientenidentitäten und EHR-Inhalten werden dabei durch den Einsatz moderner kryptografischer Algorithmen nachweisbar garantiert. Weiterhin setzen wir die Pseudonymisierungslösung zum Schutz der Privatsphäre der Patienten gegenüber Krankenversicherungsunternehmen ein. Letzteren werden lediglich genau diejenigen Patienteninformationen offenbart, die für den störungsfreien Ablauf ihrer Geschäftsprozesse nötig sind. Schließen schlagen wir eine neuartige Vorgehensweise für die Zweitverwertung der im eHealth-System gespeicherten Daten vor, die die Pseudonymisierungslösung verwendet. Diese Vorgehensweise bietet den Patienten angemessenen Schutz für ihre Privatsphäre und volle Kontrolle darüber, welche Daten für eine Zweitverwertung (z.B. für Forschungszwecke) freigegeben werden. Es wird ein prototypisches, cloudbasiertes eHealth-System vorgestellt, das die Pseudonymisierungslösung implementiert, um deren Praktikabilität zu demonstrieren und intuitive Erfahrungen zu vermitteln. Weiterhin werden, basierend auf der Implementierung, einige Abschätzungen der Performanz der Pseudonymisierungslösung angegeben

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Collision attack on NaSHA-512

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