Andre Büttner

• Hansen, Malte & Büttner, Andre (2024). Secure and Privacy-Preserving Authentication for Data Subject Rights Enforcement, Privacy and Identity Management. Sharing in a Digital World. Springer Nature. ISSN 978-3-031-57978-3. p. 175–191. doi: 10.1007/978-3-031-57978-3_12. Full text in Research Archive
• Büttner, Andre; Pedersen, Andreas Thue; Wiefling, Stephan; Gruschka, Nils & Lo Iacono, Luigi (2024). Is It Really You Who Forgot the Password? When Account Recovery Meets Risk-Based Authentication, Ubiquitous Security. Springer Nature. ISSN 9789819712748. doi: 10.1007/978-981-97-1274-8_26. Full text in Research Archive
• Büttner, Andre & Gruschka, Nils (2024). Evaluating the Influence of Multi-Factor Authentication and Recovery Settings on the Security and Accessibility of User Accounts. ICISSP. ISSN 2184-4356. doi: 10.5220/0012319000003648. Full text in Research Archive
• Pöhn, Daniela; Gruschka, Nils; Ziegler, Leonhard & Büttner, Andre (2023). A framework for analyzing authentication risks in account networks. Computers & Security. ISSN 0167-4048. 135. doi: 10.1016/j.cose.2023.103515.
• Büttner, Andre & Gruschka, Nils (2023). Protecting FIDO Extensions Against Man-in-the-Middle Attacks, Emerging Technologies for Authorization and Authentication, 5th International Workshop, ETAA 2022, Copenhagen, Denmark, September 30, 2022, Revised Selected Papers. Springer. ISSN 978-3-031-25467-3. p. 70–87. doi: 10.1007/978-3-031-25467-3_5. Show summary

  FIDO authentication has many advantages over password-based authentication, since it relies on proof of possession of a security key. It eliminates the need to remember long passwords and, in particular, is resistant to phishing attacks. Beyond that, the FIDO protocols consider protocol extensions for more advanced use cases such as online transactions. FIDO extensions, however, are not well protected from Man-in-the-Middle (MitM) attacks. This is because the specifications require a secure transport between client and server, but there exists no end-to-end protection between server and authenticator. In this paper, we discuss MitM scenarios in which FIDO extensions may be intercepted. We further propose an application-layer security protocol based on the CBOR Object Signing and Encryption (COSE) standard to mitigate these threats. This protocol was verified in a formal security evaluation using ProVerif and, finally, implemented in a proof-of-concept.

• Sæbø, Johan Ivar; Büttner, Andre; Gruschka, Nils; Jolliffe, Bob & McGee, Austin (2022). Where There is No CISO. In Zheng, Y.; Abbott, P. & Robles-Flores, J. A. (Ed.), Freedom and Social Inclusion in a Connected World 17th IFIP WG 9.4 International Conference on Implications of Information and Digital Technologies for Development. Springer. ISSN 978-3-031-19429-0. doi: 10.1007/978-3-031-19429-0_12.
• Büttner, Andre & Gruschka, Nils (2021). Enhancing FIDO Transaction Confirmation with Structured Data Formats. NIKT: Norsk IKT-konferanse for forskning og utdanning. ISSN 1892-0713. Show summary

  FIDO Transaction Confirmation is an extension for the FIDO authentication protocols to enable the verification and signing of digital transactions, e.g., for online banking. The standard currently considers only to include a transaction message text in the assertion which is signed by the user’s authenticator. However, this is not useful for more complex transactions and leaves room for ambiguities that might lead to security vulnerabilities. Therefore, we propose to include the transaction information to the FIDO protocols in a structured data format with a strictly defined schema to validate and sign transactions more reliably and securely.

• Büttner, Andre; Nguyen, Hoai Viet; Gruschka, Nils & Lo Iacono, Luigi (2021). Less is Often More: Header Whitelisting as Semantic Gap Mitigation in HTTP-Based Software Systems. In Jøsang, Audun; Futcher, Lynn & Hagen, Janne Merete (Ed.), ICT Systems Security and Privacy Protection. Springer Nature. ISSN 978-3-030-78120-0. p. 332–347. doi: 10.1007/978-3-030-78120-0_22. Show summary

  The web is the most wide-spread digital system in the world and is used for many crucial applications. This makes web application security extremely important and, although there are already many security measures, new vulnerabilities are constantly being discovered. One reason for some of the recent discoveries lies in the presence of intermediate systems—e.g. caches, message routers, and load balancers—on the way between a client and a web application server. The implementations of such intermediaries may interpret HTTP messages differently, which leads to a semantically different understanding of the same message. This so-called semantic gap can cause weaknesses in the entire HTTP message processing chain. In this paper we introduce the header whitelisting (HWL) approach to address the semantic gap in HTTP message processing pipelines. The basic idea is to normalize and reduce an HTTP request header to the minimum required fields using a whitelist before processing it in an intermediary or on the server, and then restore the original request for the next hop. Our results show that HWL can avoid misinterpretations of HTTP messages in the different components and thus prevent many attacks rooted in a semantic gap including request smuggling, cache poisoning, and authentication bypass.

View all works in Cristin