Julian Loss
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julianloss.bsky.social
Julian Loss
@julianloss.bsky.social
320 followers 140 following 37 posts
I’m a cryptographer working on digital signatures, consensus algorithms, and more. Professor for Computer Science at Ruhr University Bochum.
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Reposted by Julian Loss
cispa.de
Congrats to Dr. Benedikt Wagner for receiving the @helmholtz.de Doctoral Award! 🎉 His dissertation was supervised by Dr. @julianloss.bsky.social at CISPA. Benedikt is now bringing his cryptographic expertise to the Ethereum Foundation in Switzerland.
Wishing him continued success and inspiration!
July 9, 2025 at 11:46 AM
julianloss.bsky.social
We give a nearly optimal algorithm for the parallel broadcast problem for the t<n/2 setting using *only basic public key crypto*. Our protocol has major potential for making MPC and VSS scalable without relying on more advanced primitives. At Crypto 2025!
eprint.ing.bot ePrint Updates @eprint.ing.bot · Jun 2
Nearly Optimal Parallel Broadcast in the Plain Public Key Model (Ran Gelles, Christoph Lenzen, Julian Loss, Sravya Yandamuri) ia.cr/2025/1012
Abstract. Parallel Byzantine broadcast (PBC) (also known as Interactive Consistency), is a fundamental problem in distributed computing and cryptography which asks that all parties reliably distribute a message to all other parties. We give the first communication-efficient protocol for PBC in the model with plain public keys (i.e., no trusted dealer) which achieves security against an adaptive adversary that can corrupt up to t < n/2 parties. Our protocol runs in total communication complexity O(n²ℓlog(n)+nκ²log⁴(n)) bits to succeed with probability 1 − 2^(−κ), where ℓ is the length of a message. All prior protocols either rely on a trusted setup or require at least O(n³) communication complexity. As a stepping stone, we present a binary consensus protocol with the same resilience and success probability that sends O(n²κlog(n)+nκ²log³(n)) bits. We achieve these results based on a highly efficient gossip procedure that implements echo operations at low cost, and might prove useful in deriving further efficient protocols relying on simple cryptographic tools. Image showing part 2 of abstract.
June 2, 2025 at 3:38 PM
julianloss.bsky.social
New paper at Crypto 2025!

We revisit one of the famous works of King et al. on leader election/consensus and show that the original paper’s proof has several major gaps. Although we aren’t able to prove the original protocol secure, we suggest a suitable modification along with a full proof.
eprint.ing.bot ePrint Updates @eprint.ing.bot · Jun 2
Leader Election with Poly-logarithmic Communication Per Party (Amey Bhangale, Chen-Da Liu-Zhang, Julian Loss, Kartik Nayak, Sravya Yandamuri) ia.cr/2025/1016
Abstract. The leader election problem requires a set of n parties, out of which up to t can be Byzantine, to elect a leader uniformly at random such that no two parties disagree on the elected leader and an honest leader is elected with constant probability. The Scalable Leader Election protocol published in SODA’2006 is an important breakthrough in solving this problem efficiently for all but o(1) of the parties. They achieve a protocol for $t < (\frac{1}{3} - \epsilon)n$ (for ϵ = o(1)) in the full-information setting such that every party only sends polylog n bits. In this paper, we revisit their work and show that there are subtleties in the protocol that are not dealt with in the analysis. In particular, two mechanisms related to “silencing” parties and dealing with “bad nodes” are at odds with each other, which is why the existing analysis is insufficient. We present these concerns in detail and subsequently present a modification to their protocol with a corresponding analysis to solve leader election with the desired metrics.
June 2, 2025 at 3:36 PM
julianloss.bsky.social
We present the first three-round Schnorr threshold signature scheme with security against t<n adaptive corruptions in the plain ROM. At Crypto 2025!
eprint.ing.bot ePrint Updates @eprint.ing.bot · Jun 2
Adaptively Secure Three-Round Threshold Schnorr Signatures from DDH (Renas Bacho, Sourav Das, Julian Loss, Ling Ren) ia.cr/2025/1009
Abstract. Threshold signatures are one of the most important cryptographic primitives in distributed systems. Of particular interest is the threshold Schnorr signature, a pairing-free signature with efficient verification, compatible with standardized EdDSA (non-threshold) signature. However, most threshold Schnorr signatures have only been proven secure against a static adversary, which has to declare its corruptions before the protocol execution. Many existing adaptively secure constructions require either secure erasures or non-standard assumptions, such as the algebraic group model or hardness of the algebraic one-more discrete logarithm problem. The latest adaptively secure threshold Schnorr signature schemes under standard assumptions require five rounds of communication to create a single signature, limiting its practicality. In this work, we present Gargos, a three-round, adaptively secure threshold Schnorr signature scheme based on the hardness of the decisional Diffie-Hellman (DDH) problem in the random oracle model (ROM). Our protocol supports full corruption threshold t < n, where t is the signing threshold and n is the total number of signers. We achieve our result with an enhanced proof technique that enables us to eliminate two rounds of communication from the recent Glacius scheme (Eurocrypt 2025). We believe our techniques are of independent interest to further research in improving the round complexity of multi-party signing protocols. Image showing part 2 of abstract.
June 2, 2025 at 3:34 PM
julianloss.bsky.social
What’s up, long time no see.

I decided to move here after Twitter/X became unusable, but I realized that this was actually a great opportunity to get off of social media for good, read a book, go outside, and make some new friends.

Anyway, I’m back; what did I miss?
June 2, 2025 at 3:26 PM
julianloss.bsky.social
Crypto Eprint just broke 2k submissions in one year for the first time. Great to see the field continue to grow.
December 12, 2024 at 5:42 PM
julianloss.bsky.social
I live in Germany which is typically reluctant to adopt digital/electronic solutions to common tasks, payments in particular. However, QR-code bills have become widely popular here and I think that’s a really great development as they are so convenient. How widely are these used in other countries?
December 9, 2024 at 6:27 PM
julianloss.bsky.social
Enjoying Milan on a cold morning. What’s up @suinetwork.bsky.social
December 3, 2024 at 7:48 AM
Reposted by Julian Loss
ncrenic.bsky.social
“thanks so much for the feedback”
November 30, 2024 at 4:28 PM
julianloss.bsky.social
Is this… is this… a list of cybersecurity experts without a single cryptographer 😰?
December 1, 2024 at 5:57 AM
Reposted by Julian Loss
shravan1024.bsky.social
Here is a list of amazing (applied) crypto folks I found here:

bsky.app/profile/did:...
December 1, 2024 at 12:45 AM
julianloss.bsky.social
A wild red mushroom appears in the tall grass! ID anyone? #fungifriends
November 23, 2024 at 1:08 PM
julianloss.bsky.social
A beautiful cluster of porcelain mushrooms (oudemansiella mucida) in Alsace, France #fungifriends
November 22, 2024 at 8:55 AM
julianloss.bsky.social
Found this beautiful specimen in Alsace, France last month #fungifriends
November 22, 2024 at 7:43 AM
Reposted by Julian Loss
fakeiacr.bsky.social
Please answer / dm us to be added/ removed.

go.bsky.app/8daoJcj
November 16, 2024 at 8:07 PM
Reposted by Julian Loss
helger.bsky.social
The pack: go.bsky.app/PsmYwLY
November 15, 2024 at 7:30 AM
Reposted by Julian Loss
helger.bsky.social
Finally, a formal hello. Cryptographer. I worked on ZK (zero-knowledge) before it was cool --- I still have those voices in my head from 1998 telling me that I should do something that actually matters. One of my blunders was to recommend Estonia to use ZK in e-voting... back in 2001.
November 15, 2024 at 7:04 PM
Reposted by Julian Loss
helger.bsky.social
And a ZK starter pack. I hope many of those people will become more active here. go.bsky.app/Ap5S4vq
November 15, 2024 at 8:34 AM
julianloss.bsky.social
New paper at SODA 25:

eprint.iacr.org/2024/770

We show that you can broadcast in sublinear rounds with dishonest majority given only a bare PKI setup and a uniform CRS. Prior work in this setting assumes a trusted dealer/correlated setup.
Sublinear-Round Broadcast without Trusted Setup
Byzantine broadcast is one of the fundamental problems in distributed computing. Many of its practical applications, from multiparty computation to consensus mechanisms for blockchains, require incre...
eprint.iacr.org
November 15, 2024 at 9:47 AM
Reposted by Julian Loss
prokaryota.bsky.social
'Tis the season ... of UK research fellowship interviews! Here are some tips & tricks to help you prepare - featuring a list of 100(!) common Q&A questions elisagranato.com/how-to-apply...
How to apply for a (UK) postdoc fellowship - Elisa Granato
How to apply for a (UK) postdoc fellowship Disclaimer: this guide was written based on my experience applying for (and being awarded) a BBSRC Discovery Fellowship in 2020/2021. Some of this might appl...
elisagranato.com
November 14, 2024 at 10:52 AM
julianloss.bsky.social
I’m new here, so I’ll briefly introduce myself. My name is Julian and I’m a cryptographer who also frequently dabbles in distributed algorithms. In my free time, I train for road races (mostly half marathons) and do nerdy things. My wife and I have three adorable cats called Kami, Sweep and Janus.
November 14, 2024 at 12:29 PM
julianloss.bsky.social
Any cryptographers out there?
November 8, 2024 at 8:38 AM