Tessera

Muhammed Esgin

@mfesgin.bsky.social

Lecturer @MonashUni. Interested in various aspects of crypto(graphy): privacy-enhancing, quantum-safe, lattice-based, zero-knowledge, blockchain, … technologies Website: https://mfesgin.github.io

21 Posts141 Follower 97 Folgt

Muhammed Esgin @mfesgin.bsky.social · 7mo ago

Say hello to the first practical post-quantum private payment protocol for account-based blockchains!

ePrint Updates@eprint.ing.bot · 7mo ago

Lether: Practical Post-Quantum Account-Based Private Blockchain Payments (Hongxiao Wang, Muhammed F. Esgin, Ron Steinfeld, Siu-Ming Yiu) ia.cr/2026/076

$Abstract. We introduce Lether, the first practical account-based private block-chain payment protocol based on post-quantum lattice assumptions, following the paradigm of Anonymous Zether (FC ’19, IEEE S&P ’21). The main challenge in building such a protocol from lattices lies in the absence of core building blocks: unbounded-level additively-homomorphic multi-message multi-recipient public key encryption (mmPKE), and event-oriented linkable ring signatures with support for multiple tags (events). To address these issues, we propose a verifiable refreshable additively-homomorphic mmPKE scheme and a plug-and-play event-oriented linkable tag scheme from lattices. We believe both to be of independent interest. To achieve unbounded-level homomorphic evaluation in the lattice-based setting without relying on heavy techniques such as bootstrapping or large moduli (e.g., over 60 bits) in fully homomorphic encryption (FHE), we introduce a lightweight and blockchain-friendly mechanism called refresh. Namely, each user is required to verifiably refresh their account after a certain number of transactions. With our tailored parameter settings, the amortized per-refresh costs of communication and computation are only about 1.3% and 1.5%, respectively, of the cost of a transaction. We also optimize the implementations of LNP22 lattice-based zero-knowledge proof system (Crypto ’22) in the LaZer library (CCS ’24), to support efficient batching of various proof components. Overall, for a typical transaction, the total communication cost becomes about 68 KB, with the associated zero-knowledge proof accounting for about 51 KB of this total. Each of proof generation and verification take a fraction of a second on a standard PC. As an additional contribution, we formalize new definitions for Anonymous Zether-like protocols that more accurately capture real-world blockchain settings. These definitions are generic and are expected to benefit the broader development of account-based private blockchain payment protocols, beyond just lattice settings.$

Muhammed Esgin @mfesgin.bsky.social · last yr.

Our work on multi-message multi-recipient public key encryption is out! We build on Kyber (ML-KEM) and get great efficiency. Kudos to Hongxiao Wang for leading this work!

ePrint Updates@eprint.ing.bot · last yr.

Post-Quantum Multi-Message Public Key Encryption from Extended Reproducible PKE (Hongxiao Wang, Ron Steinfeld, Markku-Juhani O. Saarinen, Muhammed F. Esgin, Siu-Ming Yiu) ia.cr/2025/1000

Abstract. A multi-message multi-recipient Public Key Encryption (mmPKE) enables batch encryption of multiple messages for multiple independent recipients in one go, significantly reducing costs, particularly bandwidth, compared to the trivial solution of encrypting each message individually. This capability is especially critical in the post-quantum setting, where ciphertext length is typically significantly larger than the corresponding plaintext.

In this work, we first observe that the generic construction of mmPKE from reproducible PKE proposed by Bellare et al. (PKC ’03) does not apply in the lattice-based setting because existing lattice-based PKE schemes do not fit the notion of reproducible PKE. To this end, we first extend their construction by proposing a new variant of PKE, named extended reproducible PKE (XR-PKE), which enables the reproduction of ciphertexts via additional hints. However, standard lattice-based PKE schemes, such as Kyber (EuroS&P ’18), do not readily satisfy the XR PKE requirements. To construct XR-PKE from lattices, we introduce a novel technique for precisely estimating the impact of such hints on the ciphertext security while also establishing suitable parameters. This enables us to instantiate the first CPA-secure mmPKE and Multi-Key Encapsulation Mechanism (mmKEM) from the standard Module Learning with Errors (MLWE) lattice assumption, named mmCipher-PKE and mmCipher-KEM, respectively. We then extend our works to the identity-based setting and construct the first mmIBE and mmIB-KEM schemes. As a bonus contribution, we explore generic constructions of adaptively secure mmPKE, achieving security against adaptive corruption and chosen-ciphertext attacks.

We also provide an efficient implementation and thorough evaluation of the practical performance of our mmCipher. Our results show that mmCipher provides significant bandwidth and computational savings in practice, compared to the state-of-the-art. For example, for 1024 recipients, our mmCipher-KEM achieves a 23~45 times reduction in bandwidth overhead, reaching within 4~9% of the plaintext length (near optimal bandwidth), while also offering a 3~5 times reduction in computational cost.

Muhammed Esgin @mfesgin.bsky.social · last yr.

We’re getting close to ePrint 2025/555… is everyone ready for a new cryptography meltdown? #ePrint555

Muhammed Esgin @mfesgin.bsky.social · 2y ago

🎥 The recording of our inaugural Distinguished Lecture by Prof Martin Hellman is now available. Thanks to the big crowd who joined the session and for all the great questions! Recording link 👇 www.monash.edu/it/events/20... #OpenScience #GlobalSecurity #Cryptography

The Imperative for Open Science with Professor Martin Hellman

monash.edu

Muhammed Esgin@mfesgin.bsky.social · 2y ago

Just one day away from our Distinguished Lecture by ACM Turing Award recipient Prof Martin Hellman on The Imperative for Open Science and the future of geopolitical security! This is a talk not to be missed! It’s online, free & open to anyone interested! events.humanitix.com/distinguishe...

Muhammed Esgin @mfesgin.bsky.social · 2y ago

We’re honoured to host a distinguished lecture by Turing Award recipient Prof Martin Hellman on “The Imperative for Open Science”. The talk is online and open to anyone interested to join. See the attached image for more details

coyotebroad (Jayne Cravens)@coyotebroad.bsky.social · 2y ago

The wonderful @eff.org has an equally wonderful guide you can use to make it MUCH harder for Meta / Facebook / Instagram to collect and monetize your personal data. It's not super easy - offer to do this for family & neighbors who might not be able to: www.eff.org/deeplinks/20...

Mad at Meta? Don't Let Them Collect and Monetize Your Personal Data

If you’re fed up with Meta right now, you’re not alone. Meta tracks you across millions of websites and apps and its business model relies on your data. If you want to limit Meta’s ability to collect ...

eff.org

Daniel Slamanig @drl3c7er.bsky.social · 2y ago

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

PrivCrypt 2025

privcryptworkshop.github.io

Olivier @gloupin.bsky.social · 2y ago

Ecole Polytechnique is hiring 4 assistant prof / full prof in cybersecurity. (Crypto, networks, forensics, ...) Team application are welcome! gargantua.polytechnique.fr/siatel-web/a... Come join us!

Gargantua École polytechnique

Gargantua 8

gargantua.polytechnique.fr

Muhammed Esgin @mfesgin.bsky.social · 2y ago

We're hiring multiple PhD candidates for our ARC-funded project on fully-homomorphic encryption (FHE), SNARKs & more Job listing 👇 iacr.org/jobs/item/3840 Apply via docs.google.com/forms/d/e/1F... Some info on PhD at Monash/in Australia mfesgin.github.io/supervision/ Please help to share!

Fully Funded PhD student

iacr.org

Clément Canonne @ccanonne.github.io · 2y ago

💡 Making slides, giving talks, and looking for illustrations for Alice, Bob, and the whole crew? Simón Oya (UBC) has drawn fresh, beautiful ones and releasing them under CC BY-SA 4.0 license: simonoya.com/drawings/ (discovered through the #EnCOREPrivacy25 workshop)

This is a low-res sprite sheet of the pictures available

Matteo Maffei @matteomaffei.bsky.social · 2y ago

Congratulations to @erkantairi.bsky.social , former PhD student in the Security and Privacy Group at TU Wien, on his FWF Schrödinger fellowship, which will allow him to spend 2 years at UC Berkeley and then 1 year at IST Austria. I am very proud of you and all the best for the future!

Martin R. Albrecht @malb.bsky.social · 2y ago

Khanh and Eamonn are organising UK Crypto Day on 20 February at King's College London. Registration is free (and open) but required: uk-crypto-day.github.io/2025/02/20/u... Help us spread the word and see you there.

UK Crypto Day: 20 February 2025

Schedule

uk-crypto-day.github.io

Muhammed Esgin @mfesgin.bsky.social · 2y ago

This is a significant result if correct in my view. I didn’t check the technical details yet, but they get Dilithium-like signature but with about 3x reduction in signature size; almost as compact as Falcon.

ePrint Updates@eprint.ing.bot · 2y ago

Improved Rejection Sampling for Compact Lattice Signatures (Joel Gärtner) ia.cr/2024/2052

Abstract. One of the primary approaches used to construct lattice-based signature schemes is through the “Fiat-Shamir with aborts” methodology. Such a scheme may abort and restart during signing which corresponds to rejection sampling produced signatures to ensure that they follow a distribution that is independent of the secret key. This rejection sampling is only feasible when the output distribution is sufficiently wide, limiting how compact this type of signature schemes can be.

In this work, we develop a new method to construct signatures influenced by the rejection condition. This allows our rejection sampling to target significantly narrower output distributions than previous approaches, allowing much more compact signatures. The combined size of a signature and a verification key for the resulting scheme is less than half of that for ML-DSA and comparable to that of compact hash-and-sign lattice signature schemes, such as Falcon.

Muhammed Esgin @mfesgin.bsky.social · 2y ago

Apparently one does not need to fly very long to do this..

Muhammed Esgin @mfesgin.bsky.social · 2y ago

A “heuristic” proof? What does that mean???

ePrint Updates@eprint.ing.bot · 2y ago

A Heuristic Proof of P ≠ NP (Ping Wang) ia.cr/2024/2035

Abstract. The question of whether the complexity class P equals NP is a major unsolved problem in theoretical computer science. In this paper, we introduce a new language, the Add and XNOR (the negation of exclusive or (XOR)) problem, which has the simplest structure and perfect randomness, by extending the subset sum problem. We prove that P ≠ NP as it shows that an exhaustive search is necessary to solve the Add and XNOR problem. That is, problems that are verifiable in polynomial time are not necessarily solvable in polynomial time.

Muhammed Esgin @mfesgin.bsky.social · 2y ago

#Eurocrypt 2025 (initial) reviews are out! Enjoy(!) Asiacrypt everyone!

Matteo Maffei @matteomaffei.bsky.social · 2y ago

I have an opening for several Ph.D. positions at TU Wien. Topics of interest include formal methods for security (e.g., for crypto protocols and machine learning analysis), web security, and blockchains. Apply online at https://buff.ly/4fVSmBI by 19/12/2024

University Assistant Prae-Doc (all genders)

TU-ID: 192 | 2024 | 48 | 243843

buff.ly

Muhammed Esgin @mfesgin.bsky.social · 2y ago

Test-of-time award for Asiacrypt 2009 is awarded two amazing papers on lattice-based cryptography! Big congratulations to my former PhD supervisor and now close collaborator Ron Steinfeld and other recipients including Vadim Lyubashevsky and Damien Stehle!

Muhammed Esgin @mfesgin.bsky.social · 2y ago

Khoor Zruog