CRoCS wiki

Martin Ukrop

Martin Ukrop (xukrop@undisclosed.example.com) — 2026-06-13T09:20:28+00:00

Martin Ukrop

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Centre for Research on Cryptography and Security

Martin Ukrop (xukrop@undisclosed.example.com) — 2026-06-13T09:17:49+00:00

Centre for Research on Cryptography and Security

Centre for Research on Cryptography and Security started in 2006 as a laboratory at Masaryk University, Faculty of Informatics. We aim to improve security and privacy through applied research (often in cooperation with industry) and advanced education of future security professionals. Supplemented by occasional beer-touring, boardgaming and juggling.

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CRoCS's industrial partners

We cooperate on security research with many companies. Our most important partners are below.

2008 – today

Y Soft

micropayment system, software security

2014 – today

Red Hat

constant-time cryptography, usable security

2016 – today

Cryptosense

analysis of certificates

2007 – today

Monet+

secure multiparty cryptographic protocols, hardware-based authentication tokens

2014 – 2016

ESET

factors influencing security SW choice/detection of potentially unwanted applications

2014 – 2016

Oracle + NetSuite

measurement of effect of tutorial types on security policy adherence

2014 – 2016

SODAT

evaluating usability of password recovery mechanisms

2002 – 2009

NBU

design, development and evaluation of SW and HW tools for key management

2026 – today

OpenSSL

cryptography library analysis, constant-time cryptography

CRoCS's academic partners

We do multidisciplinary research cooperating with several other institutions:

1998 – today

Security Group,
Computer Laboratory, University of Cambridge

International Workshop on Security Protocols

2008 – today

Evolvable Hardware Group,
Brno University of Technology

evolutionary algorithms in cryptography

2014 – today

Interdisciplinary Research Team on Internet and Society,
Masaryk University

human aspects in security research

2014 – today

Institute of Law and Technology,
Masaryk University

law aspects of IT security

2014 – 2021

Institute of Computer Science,
Masaryk University

security awareness measurement

2015 – today

Cyber Security,
Heriot-Watt University

usable security

2016 – today

SecGroup Unive,
Ca’ Foscari University

cryptography

2017 – 2021

UCL InfoSec Group,
University College London

secure multiparty protocols

2023 – today

Tartu University,
Tartu University

X-Road and MPC signing

2019 – today

Cybernetica,
Cybernetica

Common Criteria and FIPS security certification

2023 – today

AI for Cyber Defence research centre,
The Alan Turing Institute

Analysis of privacy transactions

People at CRoCS

Regular staff

Václav (Vashek) Matyáš (head of laboratory)
Marek Sýs (assistant profesor)
Petr Švenda (associate professor)
Lukasz Michal Chmielewski (assistant professor)

PostDocs

Mariia Bakhtina (usable security)

Ph.D. students

Lenka Knapová (usable security)
Vojtěch Suchánek (elliptic curve cryptography)
Katarína Galanská (usable security)
Jan Kvapil (applied cryptography)
Roman Lacko (trusted computing)
Milan Šorf (hardware security devices)
Jiří Gavenda (Bitcoin privacy)
Yasir Yakup Demircan (machine learning for security)
Veronika Hanulíková (side-channel analysis)

External cooperation

Tamara Čierniková (InvaSys)
Ján Jančár
Adam Janovský (InvaSys)
Martin Ukrop (Red Hat)
Marek Kumpošt (Oracle | NetSuite Security)
Kamil Malinka (FIT BUT)
Zdeněk Říha (Team Leader at European Commission)
Andriy Stetsko (Oracle | NetSuite Security)
Milan Brož (OpenSSL Corporation)

Master students

David Rajnoha
Jakub Janků
Petr Hanák (side-channel analysis)

Past lab members

CoinJoin ecosystem insights for Wasabi 1.x, Wasabi 2.x and Whirlpool coordinator-based privacy mixers

Jiří Gavenda (xgavenda@undisclosed.example.com) — 2026-06-05T13:34:13+00:00

CoinJoin ecosystem insights for Wasabi 1.x, Wasabi 2.x and Whirlpool coordinator-based privacy mixers

Authors: Petr Svenda, Jiri Gavenda, Vasilios Mavroudis, Chris Hicks

Primary contact: Petr Svenda <svenda@fi.muni.cz>

Conference: PETS 2026

PRE-PRINT PDF BiBTeX

@Article{2026-pets-svenda,
 Title   = {CoinJoin ecosystem insights for Wasabi 1. x, Wasabi 2. x and Whirlpool coordinator-based privacy mixers},
 Author  = {Petr Svenda and Jiri Gavenda and Vasilios Mavroudis and Chris Hicks},
 Journal = {Proceedings on Privacy Enhancing Technologies},
 Volume  = {2},
 Pages   = {557--592},
 Year    = {2026},
 DOI     = {10.56553/popets-2026-0061},
}

Abstract

Coinjoin is a collaborative Bitcoin transaction designed to enhance users' privacy by joining coins of multiple parties. Coinjoin implementations with a centralized trust-minimized coordinator have mixed more than 391,000 bitcoins since 2018. In June 2024, law enforcement actions led to the shutdown of coordinators of all three leading coinjoin designs-Wasabi 1.x, Wasabi 2.x, and Whirlpool-prompting a proliferation of new independent coordinators. Prior studies of this ecosystem offer little information beyond coinjoin detection and aggregation of related statistics, primarily due to the unavailability of information (intentionally) obscured by coinjoins.

To overcome this limitation, we combine on-chain transaction analysis, coordinator monitoring, and active coinjoin participation, complemented by tailored analysis and visualizations, to: 1) provide a model for estimation of the number of active users at a time, 2) detect previously unknown coordinators, 3) retrospectively observe activity patterns of prominent parties, and 4) deliver continuously updated insights into the ecosystem.

We show that while Wasabi 1.x remains inactive and recently resumed Whirlpool exhibits little activity, the Wasabi 2.x mixing has exceeded pre-shutdown levels under the new coordinator kruw.io, which now accounts for 99% of mixed inputs (over 46,000 bitcoins in the past 18 months) with raising concurrently active users now estimated to 70+ in average coinjoin, providing the first data-based estimate of the participants’ anonymity set. We revealed a previously unknown but significant coordinator active from early May to November 2024, with a method capable of identifying emerging coordinators. Although WW2 conceals large-input wallet activity more effectively than WW1, it is still detected by the proposed transaction-centric liquidity analysis.

CRoCS wiki

Martin Ukrop

Martin Ukrop

Centre for Research on Cryptography and Security

Centre for Research on Cryptography and Security

Public

Researcher

Student

Lab member

CRoCS's industrial partners

We cooperate on security research with many companies. Our most important partners are below.

CRoCS's academic partners

We do multidisciplinary research cooperating with several other institutions:

People at CRoCS

Regular staff

PostDocs

Ph.D. students

External cooperation

Master students

Past lab members

CoinJoin ecosystem insights for Wasabi 1.x, Wasabi 2.x and Whirlpool coordinator-based privacy mixers

CoinJoin ecosystem insights for Wasabi 1.x, Wasabi 2.x and Whirlpool coordinator-based privacy mixers

Abstract

Research artifacts (supplementary material)