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On the asymptotic idealness of the Asmuth-Bloom threshold secret sharing scheme

Constantin Cătălin Drăgan, Ferucio Laurentiu Tiplea
2018 Information Sciences  
Constantin Cȃtȃlin Drȃgan was supported by the European Social Fund in Romania, under the responsibility of the Managing Authority for the Sectoral Operational Programme for Human Resources Development  ... 
doi:10.1016/j.ins.2018.06.046 fatcat:2dqepnf7obe5niaqlqzfbtdubm

Key-Policy Attribute-Based Encryption for Boolean Circuits from Bilinear Maps [chapter]

Ferucio Laurenţiu Ţiplea, Constantin Cătălin Drăgan
2015 Lecture Notes in Computer Science  
Drȃgan, BalkanCryptSec, Oct 16-17, 2014, Istanbul (Turkey) Introduction to ABE Our Construction Application Conclusions Extension to Boolean Circuits.  ...  Drȃgan, BalkanCryptSec, Oct 16-17, 2014, Istanbul (Turkey) Key-policy ABE for Boolean Circuits from Bilinear Maps 20/21We have proposed an ABE scheme for Boolean circuits, based on secret sharing and just  ... 
doi:10.1007/978-3-319-21356-9_12 fatcat:4msoyirvjff4lk3ngunm5g2pmy

Asymptotically Ideal CRT-based Secret Sharing Schemes for Multilevel and Compartmented Access Structures [article]

Ferucio Laurentiu Tiplea, Constantin Catalin Dragan
2018 IACR Cryptology ePrint Archive  
Multilevel and compartmented access structures are two important classes of access structures where participants are grouped into levels/compartments with different degrees of trust and privileges. The construction of secret sharing schemes for such access structures has been in the attention of researchers for a long time. Two main approaches have been taken so far: one of them is based on polynomial interpolation and the other one is based on the Chinese Remainder Theorem (CRT). In this paper
more » ... we propose the first asymptotically ideal CRT-based secret sharing schemes for (disjunctive, conjunctive) multilevel and compartmented access structures. Our approach is compositional and it is based on a variant of the Asmuth-Bloom secret sharing scheme where some participants may have public shares. Based on this, we show that the proposed secret sharing schemes for multilevel and compartmented access structures are asymptotically ideal if and only if they are based on 1-compact sequences of co-primes.
dblp:journals/iacr/TipleaD18 fatcat:53a4q7igpjfg5ldugsijumb4ey

Asymptotically ideal Chinese remainder theorem ‐based secret sharing schemes for multilevel and compartmented access structures

Ferucio Laurenţiu Ţiplea, Constantin Cătălin Drăgan
2021 IET Information Security  
-ŢIPLEA AND DRĂGAN  ...  This means that authorised sets must be able to recover all ŢIPLEA AND DRĂGAN level secrets.  ...  ŢIPLEA AND DRĂGAN -293 Under the hypothesis that all hash functions behave like random oracles, it was shown in [13, 17] that the scheme thus obtained does not leak any information (about the secret)  ... 
doi:10.1049/ise2.12014 fatcat:bwfbivqju5fnxhp7detunnu3bu

Private Votes on Untrusted Platforms: Models, Attacks and Provable Scheme

Sergiu Bursuc, Constantin-Catalin Dragan, Steve Kremer
2019 2019 IEEE European Symposium on Security and Privacy (EuroS&P)  
Modern e-voting systems deploy cryptographic protocols on a complex infrastructure involving different computing platforms and agents. It is crucial to have appropriate specification and evaluation methods to perform rigorous analysis of such systems, taking into account the corruption and computational capabilities of a potential attacker. In particular, the platform used for voting may be corrupted, e.g. infected by malware, and we need to ensure privacy and integrity of votes even in that
more » ... e. We propose a new definition of vote privacy, formalized as a computational indistinguishability game, that allows to take into account such refined attacker models; we show that the definition captures both known and novel attacks against several voting schemes; and we propose a scheme that is provably secure in this setting. We moreover formalize and machine-check the proof in the EasyCrypt theorem prover. 2019 IEEE European Symposium on Security and Privacy (EuroS&P) Setup(1 λ , (nc, I)) BB.(pk, sk) ← KGen(1 λ ) BB.(nc, I) ← (nc, I) ; BB.(reg, vote, cast, tally) ← empty ; return BB Vote(v, id, BB) (m, w) ← BB.(nc, privc[id]) return v ⊕m w BB.public: pk, pubc, nc, reg, I, vote cast, tally BB.private: sk, privc Register(1 λ , id, BB) if id ∈ BB.I BB.reg then (pk, m) ← BB.(pk, nc) w ←$ Zm ; c ← Encpk(w) BB.privc[id] ← w ; BB.pubc[id] ← c BB.reg ← BB.reg + id return BB Valid(BB) J , idL ← empty for (idi, pi) ∈ BB.cast if idi / ∈ idL then J ← J + i idL ← idL + idi return J
doi:10.1109/eurosp.2019.00050 dblp:conf/eurosp/BursucDK19 fatcat:6vavvy4rgbfenakv6coja4b4ym

Machine-Checked Proofs for Electronic Voting: Privacy and Verifiability for Belenios

Veronique Cortier, Constantin Catalin Dragan, Francois Dupressoir, Bogdan Warinschi
2018 2018 IEEE 31st Computer Security Foundations Symposium (CSF)  
We present a machine-checked security analysis of Belenios -a deployed voting protocol used already in more than 200 elections. Belenios extends Helios with an explicit registration authority to obtain eligibility guarantees. We offer two main results. First, we build upon a recent framework for proving ballot privacy in EasyCrypt. Inspired by our application to Belenios, we adapt and extend the privacy security notions to account for protocols that include a registration phase. Our analysis
more » ... ntifies a trust assumption which is missing in the existing (pen and paper) analysis of Belenios: ballot privacy does not hold if the registrar misbehaves, even if the role of the registrar is seemingly to provide eligibility guarantees. Second, we develop a novel framework for proving strong verifiability in EasyCrypt and apply it to Belenios. In the process, we clarify several aspects of the pen-and-paper proof, such as how to deal with revote policies. Together, our results yield the first machine-checked analysis of both ballot privacy and verifiability properties for a deployed electronic voting protocol. Perhaps more importantly, we identify several issues regarding the applicability of existing definitions of privacy and verifiability to systems other than Helios. While we show how to adapt the definitions to the particular case of Belenios, our findings indicate the need for more general security notions for electronic voting protocols with registration authorities.
doi:10.1109/csf.2018.00029 dblp:conf/csfw/CortierDDW18 fatcat:yca5itbsk5conofo547t7nghxy

The Search for Atmospheric Laminar Channels: Experimental Results and Method Dissemination

Iulian-Alin Roșu, Dragoș-Constantin Nica, Cătălin Dumitraș, Dragoș Chitariu, Luminița Bibire, Adrian Stelian Ghenadi, Valentin-Stelian Dragan, Maricel Agop
2021 Sensors  
In this paper, a practical application of theoretical developments found in our previous works is explored in relation to atmospheric lidar data. Multifractal structures, previously named "laminar channels", have been identified in atmospheric profiles—these exhibit cellular and self-structuring properties, and are spatially ordered across the atmospheric profile. Furthermore, these structures have been connected to the spontaneous emergence of turbulent behavior in the calm atmospheric flow.
more » ... lculating the location and occurrence of these channels can help identify features of atmospheric evolution, such as the development of the planetary boundary layer (PBL). Employing this theoretical background to atmospheric lidar data, attempts are made to confirm this suggestion and extract information about atmospheric structure and evolution by analyzing turbulent vortex scale dynamics and scale-corresponding Lyapunov exponents that form the basis of identifying the laminar channels in atmospheric lidar profiles. A parameter named "scale laminarity index" is then introduced, which quantifies the relation between vortex scale and chaoticity throughout the profile. Finally, the algorithmic methods employed in this study are described and distributed for future use.
doi:10.3390/s22010158 pmid:35009701 pmcid:PMC8749577 fatcat:4zyr2rpnafdtxnoc2pyfqj5enm

Machine-Checked Proofs of Privacy for Electronic Voting Protocols

Veronique Cortier, Constantin Catalin Dragan, Francois Dupressoir, Benedikt Schmidt, Pierre-Yves Strub, Bogdan Warinschi
2017 2017 IEEE Symposium on Security and Privacy (SP)  
doi:10.1109/sp.2017.28 dblp:conf/sp/CortierDDSSW17 fatcat:rqw3ts5xrvdt3apptmje7cc4ii

Precise and Mechanised Models and Proofs for Distance-Bounding and an Application to Contactless Payments [article]

Ioana Boureanu, Constantin Catalin Dragan, François Dupressoir, David Gérault, Pascal Lafourcade
2020 IACR Cryptology ePrint Archive  
In relay attacks, a man-in-the-middle adversary impersonates a legitimate party and makes it this party appear to be of an authenticator, when in fact they are not. In order to counteract relay attacks, distance-bounding protocols provide a means for a verifier (e.g., an payment terminal) to estimate his relative distance to a prover (e.g., a bankcard). We propose F lexiDB, a new cryptographic model for distance bounding, parameterised by different types of fine-grained corruptions. F lexiDB
more » ... ows to consider classical cases but also new, generalised corruption settings. In these settings, we exhibit new attack strategies on existing protocols. Finally, we propose a proof-of-concept mechanisation of F lexiDB in the interactive cryptographic prover EasyCrypt. We use this to exhibit a flavour of man-in-the-middle security on a variant of MasterCard's contactless-payment protocol.
dblp:journals/iacr/BoureanuDDGL20 fatcat:wztiygqnsrejdejxke3vgousqi

Towards end-to-end verifiable online voting: adding verifiability to established voting systems [article]

Mohammed Alsadi and Matthew Casey and Constantin Catalin Dragan and Francois Dupressoir and Luke Riley and Muntadher Sallal and Steve Schneider and Helen Treharne and Joe Wadsworth and Phil Wright
2021 arXiv   pre-print
Online voting for independent elections is generally supported by trusted election providers. Typically these providers do not offer any way in which a voter can verify their vote, so the providers are trusted with ballot privacy and ensuring correctness. Despite the desire to offer online voting for political elections, this lack of transparency and verifiability is often seen as a significant barrier to the large-scale adoption of online elections. Adding verifiability to an online election
more » ... creases transparency and integrity, allowing voters to verify that their vote has been recorded correctly and included in the tally. However, replacing existing online systems with those that provide verifiable voting requires new algorithms and code to be deployed, and this presents a significant business risk to commercial election providers. In this paper we present the first step in an incremental approach which minimises the business risk but demonstrates the advantages of verifiability, by developing an implementation of key elements of a Selene-based verifiability layer and adding it to an operational online voting system. Selene is a verifiable voting protocol that uses trackers to enable voters to confirm that their votes have been captured correctly while protecting voter anonymity. This results in a system where even the election authority running the system cannot change the result in an undetectable way, and gives stronger guarantees on the integrity of the election than were previously present. We explore the challenges presented by adding a verifiability layer to an operational system. We describe the results of two initial trials, which obtained that survey respondents found this form of verifiability easy to use and that they broadly appreciated it. We conclude by outlining the further steps in the road-map towards the deployment of a fully trustworthy online voting system.
arXiv:1912.00288v2 fatcat:2p5oqx3z5jgwhdeu5g6b52krkm

KYChain: User-Controlled KYC Data Sharing and Certification [article]

Constantin Cătălin Drăgan, Mark Manulis
2020 pre-print
Constantin Cȃtȃlin Drȃgan and Mark Manulis were supported by the EPSRC project TAPESTRY (EP/N02799X).  ... 
doi:10.1145/3341105.3373895 arXiv:2001.01659v1 fatcat:s36p7oop6nf2detatbia47fyde

Acknowledgment to Reviewers of Actuators in 2021

Actuators Editorial Office
2022 Actuators  
Alexandru Liu Wang Catalin Arghir Liu Yang Catalin Dumitrescu Liudmila Makarova  ...  Dorota Stachowiak Michal Puskar Doru-Laurean Baldean Michal Špiláček Dragan  ... 
doi:10.3390/act11020040 fatcat:f2nbqyunnzcflmusfxr3c36dj4

Page 3662 of Mathematical Reviews Vol. , Issue 99e [page]

1999 Mathematical Reviews  
Constantin, Adrian Constantin, Peter Constantinidis, C. P. .......... 81138,81233 Conte, Robert 35201 SORIIMIOE AS. sos onsen escinscnits 58153 Contreras, Mauricio Conway, John B.  ...  Dow, Murray PRONE 6 abt case sdesnaaecaienes ‘ RUOVEG, Ws Tih os osc oe scsederenceante Dragan, Feodor F.  ... 

Mattei Dogan's affiliation with Romanian sociology (1990-2000)
Afilierea lui Mattei Dogan la sociologia românească (1990-2000)

Cristian Preda
2022 Sociologie Româneasca = Romanian Sociology  
Stahl la refl ecția despre această temă (Drăgan, Tonoiu, & Bădescu, 1986) .  ...  Propunerea fusese făcută de către Cătălin Zamfi r 6 , ce devenise el însuși membru corespondent al instituției în 1991.  ...  Dogan, au mai fost primiți alți cinci savanți de origine română, dintr-un total de 27 de membri de onoare din străinătate cooptați în acel an: arheologul Dinu Adameșteanu, imunologul Constantin Atanasie  ... 
doi:10.33788//sr.20.1.1 fatcat:wefansenu5fnnmeybjrh4jxz6u

Conferinţa Sociologia şi Asistenţa Socială în faţa provocărilor crizei, Bucureşti, 23-24 septembrie 2011

Raluca Popescu, Monica Şerban
2011 Sociologie Româneasca = Romanian Sociology  
Pentru organizarea conferinţei, cele două instituţii s-au bucurat de sprijinul Academiei Române şi a unor institute afiliate acesteia, precum Institutul Naţional de Cercetări Economice "Constantin C.  ...  Române de Sociologie (ARS) unor personalităţi care au contribuit la dezvoltarea instituţională a sociologiei în România: Achim Mihu (Cluj), Vasile Miftode (Iaşi), Septimiu Krausz (Petroşani), Ion Drăgan  ... 
doaj:244bcb676c7e459fb1bd891bdc272491 fatcat:p377fxsdajektjqsawajtn6mam
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