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Der Campus im Frühling. Bildinformationen anzeigen

Der Campus im Frühling.

Foto: Universität Paderborn, Kamil Glabica.

Dr. Nils Löken


Digitale Zukunft

Mitglied - Doktorand

Codes und Kryptographie

Mitglied - Wissenschaftlicher Mitarbeiter

+49 5251 60-6653
Fürstenallee 11
33102 Paderborn

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Dynamic Searchable Encryption with Access Control

J. Blömer, N. Löken, in: 12th International Symposium on Foundations and Practice of Security, FPS 2019, Springer, 2019

We present a searchable encryption scheme for dynamic document collections in a multi-user scenario. Our scheme features fine-grained access control to search results, as well as access control to operations such as adding documents to the document collection, or changing individual documents. The scheme features verifiability of search results. Our scheme also satisfies the forward privacy notion crucial for the security of dynamic searchable encryption schemes.

Personal Cross-Platform Reputation

J. Blömer, N. Löken, in: Security and Trust Management, STM 2019, 2019

We propose a novel personal reputation system for cross-platform reputation. We observe that, in certain usage scenarios, e.g. crowd work, the rater anonymity property typically imposed on reputation systems is not necessary. Instead, we propose a relaxed notion of rater anonymity that is more applicable in the crowd work scenario. This allows us to construct a secure personal reputation system from simple cryptographic primitives.


Cloud Architectures for Searchable Encryption

J. Blömer, N. Löken, in: Proceedings of the 13th International Conference on Availability, Reliability and Security, ARES 2018, ACM, 2018, pp. 25:1--25:10



Searchable Encryption with Access Control

N. Löken, in: Proceedings of the 12th International Conference on Availability, Reliability and Security - ARES '17, ACM Press, 2017

Attribute-Based Encryption as a Service for Access Control in Large-Scale Organizations

J. Blömer, P. Günther, V. Krummel, N. Löken, in: Foundations and Practice of Security, Springer International Publishing, 2017, pp. 3-17


Short Group Signatures with Distributed Traceability

J. Blömer, J. Juhnke, N. Löken, in: Proceedings of the Sixth International Conference on Mathematical Aspects of Computer and Information Sciences (MACIS), 2015, pp. 166-180

Group signatures, introduced by Chaum and van Heyst [15], are an important primitive in cryptography. In group signature schemes every group member can anonymously sign messages on behalf of the group. In case of disputes a dedicated opening manager is able to trace signatures - he can extract the identity of the producer of a given signature. A formal model for static group signatures schemes and their security is defined by Bellare, Micciancio, and Warinschi [4], the case of dynamic groups is considered by Bellare, Shi, and Zhang [5]. Both models define group signature schemes with a single opening manager. The main difference between these models is that the number of group members in static schemes is fixed, while in dynamic schemes group members can join the group over time.


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