Jonas Janneck
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jonasjanneck.bsky.social
Jonas Janneck
@jonasjanneck.bsky.social
62 followers 91 following 1 posts
PhD Student in Cryptography at Ruhr University Bochum
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jonasjanneck.bsky.social
Are you looking for a signature combiner for PQC migration?
We already have combiners/hybrids for unforgeability. But do we have combiners that also preserve strong unforgeability and all BUFF properties? Now we do:
eprint.ing.bot ePrint Updates @eprint.ing.bot · Oct 8
Bird of Prey: Practical Signature Combiners Preserving Strong Unforgeability (Jonas Janneck) ia.cr/2025/1844
Abstract. Following the announcement of the first winners of the NIST post-quantum cryptography standardization process in 2022, cryptographic protocols are now undergoing migration to the newly standardized schemes. In most cases, this transition is realized through a hybrid approach, in which algorithms based on classical hardness assumptions, such as the discrete logarithm problem, are combined with post-quantum algorithms that rely on quantum-resistant assumptions, such as the Short Integer Solution (SIS) problem. A combiner for signature schemes can be obtained by simply concatenating the signatures of both schemes. This construction preserves unforgeability of the underlying schemes; however, it does not extend to stronger notions, such as strong unforgeability. Several applications, including authenticated key exchange and secure messaging, inherently require strong unforgeability, yet no existing combiner is known to achieve this property. This work introduces three practical combiners that preserve strong unforgeability and all BUFF (beyond unforgeability features) properties. Each combiner is tailored to a specific class of classical signature schemes capturing all broadly used schemes that are strongly unforgeable. Remarkably, all combiners can be instantiated with any post-quantum signature scheme in a black-box way making deployment practical and significantly less error prone. The proposed solutions are further highly efficient and have signatures that are at most the size of the (insecure) concatenation combiner. For instance, our most efficient combiner enables the combination of EdDSA with ML-DSA, yielding a signature size that is smaller than the sum of an individual EdDSA signature and an individual ML-DSA signature. Additionally, we identify a novel signature property that we call random-message validity and show that it can be used to replace the BUFF transform with the more efficient Pornin-Stern transform. The notion may be of independent interest. Image showing part 2 of abstract.
October 10, 2025 at 11:34 AM
Reposted by Jonas Janneck
eprint.ing.bot
Snake Mackerel: An Isogeny-Based AKEM Leveraging Randomness Reuse (Jonas Janneck, Jonas Meers, Massimo Ostuzzi, Doreen Riepel) ia.cr/2025/1474
Abstract. An Authenticated Key Encapsulation Mechanism (AKEM) combines public-key encryption and digital signatures to provide confidentiality and authenticity. AKEMs build the core of Hybrid Public Key Encryption (RFC 9180) and serve as a useful abstraction for messaging applications like the Messaging Layer Security (MLS) protocol (RFC 9420) and Signal’s X3DH protocol. To date, most existing AKEM constructions either rely on classical (non post-quantum) assumptions or on unoptimized black-box approaches leading to suboptimal efficiency. In this work, we choose a different abstraction level to combine KEMs and identification schemes more efficiently by leveraging randomness reuse. We construct a generic scheme and identify the necessary security requirements on the underlying KEM and identification scheme when reusing parts of their randomness. This allows for a concrete instantiation from isogenies based on the POKÉ KEM (EUROCRYPT’25) and the SQIsignHD identification scheme (EUROCRYPT’24). To be used in our black-box construction, the identification scheme requires the more advanced security property of response non-malleability. Hence, we further show that a slight modification of SQIsignHD satisfies this notion, which might be of independent interest. Putting everything together, our final scheme yields the most compact AKEM from PQ assumptions with public keys of 366 bytes and ciphertexts of 216 bytes while fulfilling the strongest confidentiality and authenticity notions. Image showing part 2 of abstract.
August 20, 2025 at 1:39 PM
Reposted by Jonas Janneck
mirohaller.bsky.social
The preliminary program for the Cryptographic Applications Workshop (CAW) at Eurocrypt'25 is out.
#CAW focuses on the construction and analysis of cryptography built for practice.
This thread gives a quick overview; the full program and abstracts are here: caw.cryptanalysis.fun#program
March 18, 2025 at 1:20 AM
Reposted by Jonas Janneck
cryptojedi.bsky.social
The 3rd edition of WISC – Women in Security and Cryptography Workshop will take place in Bochum from June 16 to 18. Already confirmed are talks by Lejla Batina, Zinaida Benenson, Shafi Goldwasser, Martina Lindorfer, and Doreen Riepel. Registration is open now! casa.rub.de/en/events/wi...
WISC | Cluster of Excellence CASA | RUB
The Women in Security and Cryptography Workshop promotes international female PhD students and outstanding female students in the field of IT security.
casa.rub.de
March 7, 2025 at 4:43 AM