Alexander Dax

dblp:240/8159 · DBLP profile ↗
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7ranked-venue papers
2as first author
6since 2021 · last 2025
0009-0007-3415-5579ORCID · verified

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Security and privacy · 7 · 2 first-author · 6 since 2021
YearPublicationVenuePosition
2025 Breaking and Provably Restoring Authentication: A Formal Analysis of SPDM 1.2 including Cross-Protocol Attacks
abstract
The SPDM (Security Protocol and Data Model) protocol is a standard under development by the DMTF consortium, and supported by major industry players including Broadcom, Cisco, Dell, Google, HP, IBM, Intel, and NVIDIA. SPDM 1.2 is a complex protocol that aims to provide platform security, for example for communicating hardware components or cloud computing scenarios. SPDM is the core security mechanism of PCI Express (PCIe) and Compute Express Link (CXL).
Cas Cremers, Alexander Dax, Aurora Naska
CCS2
2024 Keeping Up with the KEMs: Stronger Security Notions for KEMs and Automated Analysis of KEM-based Protocols
abstract
Key Encapsulation Mechanisms (KEMs) are a critical building block for hybrid encryption and modern security protocols, notably in the post-quantum setting. Given the asymmetric public key of a recipient, the primitive establishes a shared secret key between sender and recipient. In recent years, a large number of abstract designs and concrete implementations of KEMs have been proposed, e.g., in the context of the NIST process for post-quantum primitives.
Cas Cremers, Alexander Dax, Niklas Medinger
CCS2
2023 Hash Gone Bad: Automated discovery of protocol attacks that exploit hash function weaknesses
Vincent Cheval, Cas Cremers, Alexander Dax, Lucca Hirschi, Charlie Jacomme, Steve Kremer
USENIX Security Symposium3
2023 Automated Analysis of Protocols that use Authenticated Encryption: How Subtle AEAD Differences can impact Protocol Security
Cas Cremers, Alexander Dax, Charlie Jacomme, Mang Zhao
USENIX Security Symposium2
2023 Formal Analysis of SPDM: Security Protocol and Data Model version 1.2
Cas Cremers, Alexander Dax, Aurora Naska
USENIX Security Symposium2
2021 On the Soundness of Infrastructure Adversaries
abstract
Campus Companies and network operators perform risk assessment to inform policy-making, guide infrastructure investments or to comply with security standards such as ISO 27001. Due to the size and complexity of these networks, risk assessment techniques such as attack graphs or trees describe the attacker with a finite set of rules. This characterization of the attacker can easily miss attack vectors or overstate them, potentially leading to incorrect risk estimation. In this work, we propose the first methodology to justify a rule-based attacker model. Conceptually, we add another layer of abstraction on top of the symbolic model of cryptography, which reasons about protocols and abstracts cryptographic primitives. This new layer reasons about Internet-scale networks and abstracts protocols.We show, in general, how the soundness and completeness of a rule-based model can be ensured by verifying trace properties, linking soundness to safety properties and completeness to liveness properties. We then demonstrate the approach for a recently proposed threat model that quantifies the confidentiality of email communication on the Internet, including DNS, DNSSEC, and SMTP. Using off-the-shelf protocol verification tools, we discover two flaws in their threat model. After fixing them, we show that it provides symbolic soundness.
Alexander Dax, Robert Künnemann
CSF1
2019 How to Wrap it up - A Formally Verified Proposal for the use of Authenticated Wrapping in PKCS#11
abstract
Being the most widely used and comprehensive standard for hardware security modules, cryptographic tokens and smart cards, PKCS#11 has been the subject of academic study for years. PKCS#11 provides a key store that is separate from the application, so that, ideally, an application never sees a key in the clear. Again and again, researchers have pointed out the need for an import/export mechanism that ensures the integrity of the permissions associated to a key. With version 2.40, for the first time, the standard included authenticated deterministic encryption schemes. The interface to this operation is insecure, however, so that an application can get the key in the clear, subverting the purpose of using a hardware security module. This work proposes a formal model for the secure use of authenticated deterministic encryption in PKCS#11, including concrete API changes to allow for secure policies to be implemented. Owing to the authenticated encryption mechanism, the policy we propose provides more functionality than any policy proposed so far and can be implemented without access to a random number generator. Our results cover modes of operation that rely on unique initialisation vectors (IVs), like GCM or CCM, but also modes that generate synthetic IVs. We furthermore provide a proof for the deduction soundness of our modelling of deterministic encryption in Böhl et.al.'s composable deduction soundness framework.
Alexander Dax, Robert Künnemann, Sven Tangermann, Michael Backes 0001
CSF1