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Posts by Christoph Striecks

PrivCrypt 2026

I am co-organising (with @drl3c7er.bsky.social and Lucjan Hanzlik) a workshop on Privacy-Enhancing Cryptography in Rome on May 10 as an affiliated event to IACR Eurocrypt. Submit your best PEC-work (3-page extended abstract) for presentation by February 25th: privcryptworkshop.github.io

2 months ago 11 9 1 0
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Postdoc Position in Lattice-Based Cryptography We are recruiting a postdoc to work with us on “practical advanced post-quantum cryptography from lattices”, the title of my ERC selected, UKRI Frontier Research funded project: Standardisation eff…

We are recruiting for at Postdoc Position in Lattice-Based Cryptography at King's College London martinralbrecht.wordpress.com/2025/08/24/p...

7 months ago 8 5 0 0

Grateful to @iacrcrypto.bsky.social for acting quickly to address serious concerns from the community.

1 year ago 25 6 1 0

We have extended the submission deadline for the International Workshop on Foundations and Applications of Privacy-Enhancing Cryptography (PrivCrypt) by two weeks to April 4, 2025, AoE. Please help spread the word and consider submitting your work to join us in Munich in Summer 😎

1 year ago 3 5 0 0
PhDs / PostDocs in Cryptographic Engineering

If you are looking for a PhD or PostDoc position in Cryptographic Engineering, please check the openings of Michael Hutter at our Research Institute CODE here in beautiful Munich. Please consider and help spread the word: iacr.org/jobs/item/3908

1 year ago 11 12 0 1
Abstract. Succinct non-interactive arguments of knowledge (SNARKs) are variants of non-interactive zero-knowledge proofs (NIZKs) in which complex statements can be proven in a compact way. SNARKs have had tremendous impact in several areas of cryptography, including verifiable computing, blockchains, and anonymous communication. A recurring concept in many applications is the concept of recursive SNARKs, in which a proof references a previous proof to show an evolved statement.

In this work, we investigate malleable SNARKs, a generalization of this concept of recursion. An adaptation of the existing concept of malleable NIZKs, malleable SNARKs allow to modify SNARK proofs to show related statements, but such that such mauled proofs are indistinguishable from “properly generated” fresh proofs of the related statement. We show how to instantiate malleable SNARKs for universal languages and relations, and give a number of applications: the first post-quantum RCCA-secure rerandomizable and updatable encryption schemes, a generic construction of reverse firewalls, and an unlinkable (i.e., computation-hiding) targeted malleable homomorphic encryption scheme.

Technically, our malleable SNARK construction relies on recursive proofs, but with a twist: in order to support the strong indistinguishability properties of mauled and fresh SNARK proofs, we need to allow an unbounded recursion depth. To still allow for a reasonable notion of extractability in this setting (and in particular to guarantee that extraction eventually finishes with a “proper” witness that does not refer to a previous SNARK proof), we rely on a new and generic computational primitive called adversarial one-way function (AOWF) that may be of independent interest. We give an AOWF candidate and prove it secure in the random oracle model.

Abstract. Succinct non-interactive arguments of knowledge (SNARKs) are variants of non-interactive zero-knowledge proofs (NIZKs) in which complex statements can be proven in a compact way. SNARKs have had tremendous impact in several areas of cryptography, including verifiable computing, blockchains, and anonymous communication. A recurring concept in many applications is the concept of recursive SNARKs, in which a proof references a previous proof to show an evolved statement. In this work, we investigate malleable SNARKs, a generalization of this concept of recursion. An adaptation of the existing concept of malleable NIZKs, malleable SNARKs allow to modify SNARK proofs to show related statements, but such that such mauled proofs are indistinguishable from “properly generated” fresh proofs of the related statement. We show how to instantiate malleable SNARKs for universal languages and relations, and give a number of applications: the first post-quantum RCCA-secure rerandomizable and updatable encryption schemes, a generic construction of reverse firewalls, and an unlinkable (i.e., computation-hiding) targeted malleable homomorphic encryption scheme. Technically, our malleable SNARK construction relies on recursive proofs, but with a twist: in order to support the strong indistinguishability properties of mauled and fresh SNARK proofs, we need to allow an unbounded recursion depth. To still allow for a reasonable notion of extractability in this setting (and in particular to guarantee that extraction eventually finishes with a “proper” witness that does not refer to a previous SNARK proof), we rely on a new and generic computational primitive called adversarial one-way function (AOWF) that may be of independent interest. We give an AOWF candidate and prove it secure in the random oracle model.

Image showing part 2 of abstract.

Image showing part 2 of abstract.

Malleable SNARKs and Their Applications (Suvradip Chakraborty, Dennis Hofheinz, Roman Langrehr, Jesper Buus Nielsen, Christoph Striecks, Daniele Venturi) ia.cr/2025/311

1 year ago 2 2 0 0
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QSHC 2025 About the Workshop This workshop aims to explore the synergies between (symmetric/asymmetric) quantum-safe and quantum cryptography. A leading example is the design of Hybrid Authenticated Key Exchang...

Ludovic Perret (EPITA & SORBONNE) and I are organizing a workshop on "Quantum-Safe Hybrid Cryptography (QSHC)" under the umbrella of ACNS 2025.

Please consider submitting a contributed talk (2-page abstract) and helping us spread the word.

Link: sites.google.com/view/qshc25/...

1 year ago 4 1 0 0
PrivCrypt 2025

We are organising the International Workshop on Foundations and Applications of Privacy-Enhancing Cryptography (PrivCrypt) - co-located with ACNS 2025 end of June in beautiful Munich.

Submission deadline is March 21, 2025 (AoE).

Please help spread the word! 🙏

privcryptworkshop.github.io

1 year ago 15 7 0 1