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85 results on '"Fitzi, Matthias"'

1. FairTraDEX: A Decentralised Exchange Preventing Value Extraction

Author

McMenamin, Conor, Daza, Vanesa, Fitzi, Matthias, and O'Donoghue, Padraic

Subjects
Computer Science - Computer Science and Game Theory, Computer Science - Cryptography and Security
Abstract

We present FairTraDEX, a decentralized exchange (DEX) protocol based on frequent batch auctions (FBAs), which provides formal game-theoretic guarantees against extractable value. FBAs when run by a trusted third-party provide unique game-theoretic optimal strategies which ensure players are shown prices equal to the liquidity provider's fair price, excluding explicit, pre-determined fees. FairTraDEX replicates the key features of an FBA that provide these game-theoretic guarantees using a combination of set-membership in zero-knowledge protocols and an escrow-enforced commit-reveal protocol. We extend the results of FBAs to handle monopolistic and/or malicious liquidity providers. We provide real-world examples that demonstrate that the costs of executing orders in existing academic and industry-standard protocols become prohibitive as order size increases due to basic value extraction techniques, popularized as maximal extractable value. We further demonstrate that FairTraDEX protects against these execution costs, guaranteeing a fixed fee model independent of order size, the first guarantee of it's kind for a DEX protocol. We also provide detailed Solidity and pseudo-code implementations of FairTraDEX, making FairTraDEX a novel and practical contribution.

Published
2022

2. Minotaur: Multi-Resource Blockchain Consensus

Author

Fitzi, Matthias, Wang, Xuechao, Kannan, Sreeram, Kiayias, Aggelos, Leonardos, Nikos, Viswanath, Pramod, and Wang, Gerui

Subjects
Computer Science - Cryptography and Security
Abstract

Resource-based consensus is the backbone of permissionless distributed ledger systems. The security of such protocols relies fundamentally on the level of resources actively engaged in the system. The variety of different resources (and related proof protocols, some times referred to as PoX in the literature) raises the fundamental question whether it is possible to utilize many of them in tandem and build multi-resource consensus protocols. The challenge in combining different resources is to achieve fungibility between them, in the sense that security would hold as long as the cumulative adversarial power across all resources is bounded. In this work, we put forth Minotaur, a multi-resource blockchain consensus protocol that combines proof-of-work (PoW) and proof-of-stake (PoS), and we prove it optimally fungible. At the core of our design, Minotaur operates in epochs while continuously sampling the active computational power to provide a fair exchange between the two resources, work and stake. Further, we demonstrate the ability of Minotaur to handle a higher degree of work fluctuation as compared to the Bitcoin blockchain; we also generalize Minotaur to any number of resources. We demonstrate the simplicity of Minotaur via implementing a full stack client in Rust (available open source). We use the client to test the robustness of Minotaur to variable mining power and combined work/stake attacks and demonstrate concrete empirical evidence towards the suitability of Minotaur to serve as the consensus layer of a real-world blockchain., Comment: To appear in ACM CCS 2022

Published
2022
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3. Ofelimos: Combinatorial Optimization via Proof-of-Useful-Work : A Provably Secure Blockchain Protocol

Author

Fitzi, Matthias, Kiayias, Aggelos, Panagiotakos, Giorgos, Russell, Alexander, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Dodis, Yevgeniy, editor, and Shrimpton, Thomas, editor

Published
2022
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4. Fast Isomorphic State Channels

Author

Chakravarty, Manuel M. T., Coretti, Sandro, Fitzi, Matthias, Gaži, Peter, Kant, Philipp, Kiayias, Aggelos, Russell, Alexander, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Borisov, Nikita, editor, and Diaz, Claudia, editor

Published
2021
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6. Ledger Combiners for Fast Settlement

Author

Fitzi, Matthias, Gaži, Peter, Kiayias, Aggelos, Russell, Alexander, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Pass, Rafael, editor, and Pietrzak, Krzysztof, editor

Published
2020
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7. Fast Isomorphic State Channels

Author

Chakravarty, Manuel M. T., primary, Coretti, Sandro, additional, Fitzi, Matthias, additional, Gaži, Peter, additional, Kant, Philipp, additional, Kiayias, Aggelos, additional, and Russell, Alexander, additional

Published
2021
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8. The non-locality of n noisy Popescu-Rohrlich boxes

Author

Fitzi, Matthias, Hänggi, Esther, Scarani, Valerio, and Wolf, Stefan

Subjects
Quantum Physics
Abstract

We quantify the amount of non-locality contained in n noisy versions of so-called Popescu-Rohrlich boxes (PRBs), i.e., bipartite systems violating the CHSH Bell inequality maximally. Following the approach by Elitzur, Popescu, and Rohrlich, we measure the amount of non-locality of a system by representing it as a convex combination of a local behaviour, with maximal possible weight, and a non-signalling system. We show that the local part of n systems, each of which approximates a PRB with probability $1-\epsilon$, is of order $\Theta(\epsilon^{\lceil n/2\rceil})$ in the isotropic, and equal to $(3\epsilon)^n$ in the maximally biased case., Comment: 14 pages, v2: published version

Published
2008
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10. A Quantum solution to the Byzantine agreement problem

Author

Fitzi, Matthias, Gisin, Nicolas, and Maurer, Ueli

Subjects
Quantum Physics
Abstract

We present a solution to an old and timely problem in distributed computing. Like Quantum Key Distribution (QKD), quantum channels make it possible to achieve taks classically impossible. However, unlike QKD, here the goal is not secrecy but agreement, and the adversary is not outside but inside the game, and the resources require qutrits., Comment: 4 pages, 1 figure

Published
2001
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11. Minotaur

Author

Fitzi, Matthias, primary, Wang, Xuechao, additional, Kannan, Sreeram, additional, Kiayias, Aggelos, additional, Leonardos, Nikos, additional, Viswanath, Pramod, additional, and Wang, Gerui, additional

Published
2022
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12. FairTraDEX

Author

McMenamin, Conor, primary, Daza, Vanesa, additional, Fitzi, Matthias, additional, and O'Donoghue, Padraic, additional

Published
2022
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13. On the Number of Synchronous Rounds Sufficient for Authenticated Byzantine Agreement

Author

Fitzi, Matthias, Nielsen, Jesper Buus, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, and Keidar, Idit, editor

Published
2009
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14. MPC vs. SFE: Perfect Security in a Unified Corruption Model

Author

Beerliová-Trubíniová, Zuzana, Fitzi, Matthias, Hirt, Martin, Maurer, Ueli, Zikas, Vassilis, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, and Canetti, Ran, editor

Published
2008
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15. Towards Optimal and Efficient Perfectly Secure Message Transmission

Author

Fitzi, Matthias, Franklin, Matthew, Garay, Juan, Vardhan, S. Harsha, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Rangan, C. Pandu, editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, and Vadhan, Salil P., editor

Published
2007
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16. Secure Protocols with Asymmetric Trust

Author

Damgård, Ivan, Desmedt, Yvo, Fitzi, Matthias, Nielsen, Jesper Buus, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, and Kurosawa, Kaoru, editor

Published
2007
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17. Round-Optimal and Efficient Verifiable Secret Sharing

Author

Fitzi, Matthias, Garay, Juan, Gollakota, Shyamnath, Rangan, C. Pandu, Srinathan, Kannan, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Dough, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Halevi, Shai, editor, and Rabin, Tal, editor

Published
2006
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18. Unconditionally Secure Constant-Rounds Multi-party Computation for Equality, Comparison, Bits and Exponentiation

Author

Damgård, Ivan, Fitzi, Matthias, Kiltz, Eike, Nielsen, Jesper Buus, Toft, Tomas, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Dough, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Halevi, Shai, editor, and Rabin, Tal, editor

Published
2006
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19. Pseudo-signatures, Broadcast, and Multi-party Computation from Correlated Randomness

Author

Fitzi, Matthias, Wolf, Stefan, Wullschleger, Jürg, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, and Franklin, Matt, editor

Published
2004
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20. Multi-party Computation with Hybrid Security

Author

Fitzi, Matthias, Holenstein, Thomas, Wullschleger, Jürg, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Cachin, Christian, editor, and Camenisch, Jan L., editor

Published
2004
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39. Byzantine Agreement Given Partial Broadcast

Author

Considine, Jeffrey, Fitzi, Matthias, Franklin, Matthew, Levin, Leonid A., Maurer, Ueli, Metcalf, David, Considine, Jeffrey, Fitzi, Matthias, Franklin, Matthew, Levin, Leonid A., Maurer, Ueli, and Metcalf, David

Abstract

This paper considers unconditionally secure protocols for reliable broadcast among a set of n players, where up to t of the players can be corrupted by a (Byzantine) adversary but the remaining h = n - t players remain honest. In the standard model with a complete, synchronous network of bilateral authenticated communication channels among the players, broadcast is achievable if and only if 2n/h < 3. We show that, by extending this model by the existence of partial broadcast channels among subsets of b players, global broadcast can be achieved if and only if the number h of honest players satisfies 2n/h < b + 1. Achievability is demonstrated by protocols with communication and computation complexities polynomial in the size of the network, i.e., in the number of partial broadcast channels. A respective characterization for the related consensus problem is also given

Published
2018

40. Minimal Complete Primitives for Secure Multi-Party Computation

Author

Fitzi, Matthias, Garay, Juan A., Maurer, Ueli, Ostrovsky, Rafail, Fitzi, Matthias, Garay, Juan A., Maurer, Ueli, and Ostrovsky, Rafail

Abstract

The study of minimal cryptographic primitives needed to implement secure computation among two or more players is a fundamental question in cryptography. The issue of complete primitives for the case of two players has been thoroughly studied. However, in the multi-party setting, when there are n > 2 players and t of them are corrupted, the question of what are the simplest complete primitives remained open for t ≥ n/3. (A primitive is called complete if any computation can be carried out by the players having access only to the primitive and local computation.) In this paper we consider this question, and introduce complete primitives of minimal cardinality for secure multi-party computation. The cardinality issue (number of players accessing the primitive) is essential in settings where primitives are implemented by some other means, and the simpler the primitive the easier it is to realize. We show that our primitives are complete and of minimal cardinality possible for most cases

Published
2018

42. How to Share a Key (Invited paper)

Author

Fitzi, Matthias, Nielsen, Jesper Buus, and Wolf, Stefan

Abstract

The problem of asynchronous perfectly secure communicationvia one-time pads (OTP) has been recently introducedby Di Crescenzo and Kiayias. There, several players share thesame OTP to be used in parallel but it is not known in advancewhich players will consume how many bits of the pad. Based onthe common OTP and only partial local knowledge of how manykey bits have already been used by each other player, the goal isto commonly consume as many key bits as possible without anyoverlap.In this paper, we consider a related problem with immediateimplications to the previous model. We consider n players toshare the same k keys of length ` bits. The goal is to assigna key sequence to each player such that, for as many keys aspossible and independently of which player uses how many ofthem, it is guaranteed that all used keys are independent. Such anassignment is called loss-free if k keys can always be consumedindependently. Note that, in contrast to the previous model, theplayers are ignorant of each other’s key consumptions.We first observe a simple loss-free solution for the case thatthe key is of certain (small) minimal length `. Furthermore, forthe case of key length ` = 1 (the most general case), we showthat loss-free assignments are possible if and only if the numberof players is at most three.Our solutions directly apply to the model of Di Crescenzoand Kiayias. For the case n = 3, we strictly improve over theirsolution. For n > 3, we still partially improve over their solutiondespite the fact that our construction is simple and oblivious.

Published
2007

43. Unconditionally Secure Constant-Rounds Multi-party Computation for Equality, Comparison, Bits and Exponentiation

Author

Damgård, Ivan Bjerre, Nielsen, Jesper Buus, Toft, Tomas, Kiltz, Eike, Fitzi, Matthias, Halevi, Shai, and Rabin, Tal

Abstract

We show that if a set of players hold shares of a value aFp for some prime p (where the set of shares is written [a] p ), it is possible to compute, in constant rounds and with unconditional security, sharings of the bits of a, i.e., compute sharings [a 0] p , ..., [a ℓ− − 1] p such that ℓ = ⌈ log2 p ⌉, a 0,...,a l − 1 ∈ {0,1} and a = ∑ i = 0 ℓ− − 1 a i 2 i . Our protocol is secure against active adversaries and works for any linear secret sharing scheme with a multiplication protocol. The complexity of our protocol is (llogl) invocations of the multiplication protocol for the underlying secret sharing scheme, carried out in (1) rounds.This result immediately implies solutions to other long-standing open problems such as constant-rounds and unconditionally secure protocols for deciding whether a shared number is zero, comparing shared numbers, raising a shared number to a shared exponent and reducing a shared number modulo a shared modulus.

Published
2006

44. How to Split a Shared Secret into Shared Bits in Constant-Round

Author

Damgård, Ivan Bjerre, Fitzi, Matthias, Nielsen, Jesper Buus, and Toft, Tomas

Abstract

We show that if a set of players hold shares of a value $a\in Z_p$ for some prime $p$ (where the set of shares is written $[a]_p$), it is possible to compute, in constant round and with unconditional security, sharings of the bits of $a$, i.e.~compute sharings $[a_0]_p, \ldots, [a_{l-1}]_p$ such that $l = \lceil \log_2(p) \rceil$, $a_0, \ldots, a_{l-1} \in \{0,1\}$ and $a = \sum_{i=0}^{l-1} a_i 2^i$. Our protocol is secure against active adversaries and works for any linear secret sharing scheme with a multiplication protocol. This result immediately implies solutions to other long-standing open problems, such as constant-round and unconditionally secure protocols for comparing shared numbers and deciding whether a shared number is zero. The complexity of our protocol is $O(l \log(l))$ invocations of the multiplication protocol for the underlying secret sharing scheme, carried out in $O(1)$.

Published
2005

50. Generalized communication and security models in Byzantine agreement

Author

Fitzi, Matthias

Subjects
Data processing, computer science, VERTEILTE ANWENDUNGEN + CLOUD COMPUTING + GRID COMPUTING (COMPUTERSYSTEME), DATA SECURITY + DATA PROTECTION (OPERATING SYSTEMS), DATA COMMUNICATIONS (COMPUTER SYSTEMS), KRYPTOGRAPHIE (INFORMATIONSTHEORIE), DATENKOMMUNIKATION (COMPUTERSYSTEME), DATENSICHERHEIT + DATENSCHUTZ (BETRIEBSSYSTEME), DISTRIBUTED APPLICATIONS + CLOUD COMPUTING + GRID COMPUTING (COMPUTER SYSTEMS), CRYPTOGRAPHY (INFORMATION THEORY)
Published
2002
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