This paper shows a generic and simple conversion from weak asymmetric and symmetric encryption schemes into an asymmetric encryption scheme which is secure in a very strong sense- indistinguishability against adaptive chosen-ciphertext attacks in the random oracle model. In particular, this conversion can be applied efficiently to an asymmetric encryption scheme that provides a large enough coin space and, for every message, many enough variants of the encryption, like the ElGamal encryption scheme.

Secure integration of asymmetric and symmetric encryption schemes

Modern key exchange protocols are usually based on the Diffie–Hellman (DH) primitive. The beauty of this primitive, among other things, is its potential reusage of key shares: DH shares can be either used a single time or in multiple runs. Since DH-based protocols are insecure against quantum adversaries, alternative solutions have to be found when moving to the post-quantum setting. However, most post-quantum candidates, including schemes based on lattices and even supersingular isogeny DH, are not known to be secure under key reuse. In particular, this means that they cannot be necessarily deployed as an immediate DH substitute in protocols.

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Towards Post-Quantum Security for Signal's X3DH Handshake

The technology of modern vehicles is currently undergoing a major transformation with increased communication and the introduction of new protocols. It is essential that these protocols are secure and do not allow attacks on the vehicle. In this paper, we discuss how formal models can be used to verify the security of protocols used in modern vehicles and propose new group membership authentication properties for shared key scenarios used in some automotive protocols. Our focus is on tool-based analysis for which we provide an overview of suitable tools, analyze the current status of (automotive) protocol analysis and, as an example, analyze AUTOSAR’s Secure Onboard Communication (SecOC) with the Tamarin tool. Our results show that tool-based formal analysis is a relatively quick and easy way to assess the security of protocols and can help to increase the security of modern vehicles.

Security Analysis of Automotive Protocols

5G saw the introduction of an encrypted user identifier, the Subscriber Concealed Identifier (SUCI), to provide confidentiality of the subscriber's whereabouts and identities. The SUCI protects the new generation of cellular networks against tracking devices, so-called IMSI-catchers, which have undermined users' confidentiality ever since the inception of cellular networks. However, the potential advent of large-scale quantum computers in the near future threatens to compromise the confidentiality provided by the SUCI yet again. The security of the public-key cryptography that underpins the SUCI relies on the hardness of the discrete logarithm problem. Using Shor's algorithm, a quantum adversary could break the SUCI's cryptography and once more gain the capability to track and identify users. Advancements in quantum computing are unpredictable, and a breakthrough might be only a decade away. Given the slow nature of standards and their implementation, it is thus necessary to already integrate now quantum-resistant cryptography into the current and also next-generation (6G) cellular networks. To contribute to this development, we propose a post-quantum secure scheme for the SUCI calculation, \textttKEMSUCI. To this end, we first analyze the weak points in the current SUCI calculation scheme when considering quantum attacks. We then describe an alternative SUCI calculation scheme based on post-quantum secure key-encapsulation mechanisms (KEMs). Our proposed scheme can use any of the KEMs submitted to the NIST call for standardization of post-quantum secure cryptography (PQC) schemes. For the usage in \textttKEMSUCI, the KEM should provide efficient execution on a SIM card and induce little network communication overhead. We evaluate all of the NIST PQC finalists under these aspects and identify Kyber and Saber as the best fit. Instantiated with these KEMs, \textttKEMSUCI can be integrated into 5G and 6G. Compared to the existing SUPI protection schemes, \textttKEMSUCI exhibits faster execution speed and only little communication overhead.

A Post-Quantum Secure Subscription Concealed Identifier for 6G

While quantum computers are rapidly becoming more powerful, the current cryptographic infrastructure is imminently threatened. In a preventive manner, the U.S. National Institute of Standards and Technology (NIST) has initiated a process to evaluate quantum-resistant cryptosystems, to form the first post-quantum (PQ) cryptographic standard. Classic McEliece (CM) is one of the most prominent cryptosystems considered for standardization in NIST’s PQ cryptography contest. However, its computational cost poses notable challenges to a big fraction of existing computing devices. This work presents an HLS-based, HW/SW co-design acceleration of the CM Key Encapsulation Mechanism (CM KEM). We demonstrate significant maximum speedups of up to 55.2 ×, 3.3 ×, and 8.7 × in the CM KEM algorithms of key generation, encapsulation, and decapsulation respectively, comparing to a SW-only scalar implementation.

HLS-Based HW/SW Co-Design of the Post-Quantum Classic McEliece Cryptosystem

In this paper we present PQ-WireGuard, a post-quantum variant of the handshake in the WireGuard VPN protocol (NDSS 2017). Unlike most previous work on post-quantum security for real-world protocols, this variant does not only consider post-quantum confidentiality (or forward secrecy) but also post-quantum authentication. To achieve this, we replace the Diffie-Hellman-based handshake by a more generic approach only using key-encapsulation mechanisms (KEMs). We establish security of PQ-WireGuard, adapting the security proofs for WireGuard in the symbolic model and in the standard model to our construction. We then instantiate this generic construction with concrete post-quantum secure KEMs, which we carefully select to achieve high security and speed. We demonstrate competitiveness of PQ-WireGuard presenting extensive bench-marking results comparing to widely deployed VPN solutions.

Post-quantum WireGuard

We introduce PQNoise, a post-quantum variant of the Noise framework. We demonstrate that it is possible to replace the Diffie-Hellman key-exchanges in Noise with KEMs in a secure way. A challenge is the inability to combine key pairs of KEMs, which can be resolved by certain forms of randomness-hardening for which we introduce a formal abstraction. We provide a generic recipe to turn classical Noise patterns into PQNoise patterns. We prove that the resulting PQNoise patterns achieve confidentiality and authenticity in the fACCE model. Moreover we show that for those classical Noise-patterns that have been conjectured or proven secure in the fACCE model our matching PQNoise patterns eventually achieve the same security. Our security proof is generic and applies to any valid PQNoise pattern. This is made possible by another abstraction, called a hash-object, which hides the exact workings of how keying material is processed in an abstract stateful object that outputs pseudorandom keys under different corruption patterns. We also show that the hash chains used in Noise are a secure hash-object. Finally, we demonstrate the practicality of PQNoise delivering benchmarks for several base patterns.

Post Quantum Noise

In this work we take a formal look at deniability in group chat applications and introduce the concept of "epochal signatures" that allows to turn many secure group chat protocols into deniable ones. Intuitively, the transform works for protocols that use signatures for authentication and that become deniable if the signatures are removed. In contrast to previous proposals that use signatures for entity authentication, like mpOTR (CCS’09), our construction does not require pairwise key establishment of participants and allows to add and remove participants without requiring to re-initialize the chat. These properties allow the deployment in protocols that are also designed to scale to very large groups. Finally, we construct a practical epochal signature scheme from generic primitives and prove it secure.

Epochal Signatures for Deniable Group Chats

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Florian Weber

Papers

Post-quantum WireGuard

Post Quantum Noise

Epochal Signatures for Deniable Group Chats

Post-quantum WireGuard.