scholarly journals SwapCT: Swap Confidential Transactions for Privacy-Preserving Multi-Token Exchanges

2021 ◽  
Vol 2021 (4) ◽  
pp. 270-290
Author(s):  
Felix Engelmann ◽  
Lukas Müller ◽  
Andreas Peter ◽  
Frank Kargl ◽  
Christoph Bösch
Keyword(s):  
Formal Model ◽  
Privacy Preserving ◽  
Third Party ◽  
Independent Interest ◽  
Signature Scheme ◽  
Fair Exchange ◽  
Prototype Implementation ◽  
Trusted Third Party ◽  
Efficient Performance ◽  
Exchange Transactions

Abstract Decentralized token exchanges allow for secure trading of tokens without a trusted third party. However, decentralization is mostly achieved at the expense of transaction privacy. For a fair exchange, transactions must remain private to hide the participants and volumes while maintaining the possibility for noninteractive execution of trades. In this paper we present a swap confidential transaction system (SwapCT) which is related to ring confidential transactions (e.g. used in Monero) but supports multiple token types to trade among and enables secure, partial transactions for noninteractive swaps. We prove that SwapCT is secure in a strict, formal model and present its efficient performance in a prototype implementation with logarithmic signature sizes for large anonymity sets. For our construction we design an aggregatable signature scheme which might be of independent interest. Our SwapCT system thereby enables a secure and private exchange for tokens without a trusted third party.

Privacy-Preserving Protocol for Atomic Swap Between Blockchains

2020 ◽  
Author(s):  
Kiran Gurung
Keyword(s):  
Secret Sharing ◽  
Privacy Preserving ◽  
The Other ◽  
Third Party ◽  
Fair Exchange ◽  
Trusted Third Party ◽  
Generic Framework ◽  
Ring Signatures ◽  
Successful Execution

Atomic swap facilitates fair exchange of cryptocurrencies without the need for a trusted authority. It is regarded as one of the prominent technologies for the cryptocurrency ecosystem, helping to realize the idea of a decentralized blockchain introduced by Bitcoin. However, due to the heterogeneity of the cryptocurrency systems, developing efficient and privacy-preserving atomic swap protocols has proven challenging. In this thesis, we propose a generic framework for atomic swap, called PolySwap, that enables fair ex-change of assets between two heterogeneous sets of blockchains. Our construction 1) does not require a trusted third party, 2) preserves the anonymity of the swap by preventing transactions from being linked or distinguished, and 3) does not require any scripting capability in blockchain. To achieve our goal, we introduce a novel secret sharing signature(SSSig) scheme to remove the necessity of common interfaces between blockchains in question. These secret sharing signatures allow an arbitrarily large number of signatures to be bound together such that the release of any single transaction on one blockchain opens the remaining transactions for the other party, allowing multi-chain atomic swaps while still being indistinguishable from a standard signature. We provide construction details of secret sharing signatures for ECDSA, Schnorr, and CryptoNote-style Ring signatures. Additionally, we provide an alternative contingency protocol, allowing parties to exchange to and from blockchains that do not support any form of time-locked escape transactions. A successful execution of PolySwap shows that it takes 8.3 seconds to complete an atomic swap between Bitcoin's Testnet3 and Ethereum's Rinkeby (excluding confirmation time).

scholarly journals Mainzelliste SecureEpiLinker (MainSEL): Privacy-Preserving Record Linkage using Secure Multi-Party Computation

2020 ◽  
Author(s):  
Sebastian Stammler ◽  
Tobias Kussel ◽  
Phillipp Schoppmann ◽  
Florian Stampe ◽  
Galina Tremper ◽  
...  
Keyword(s):  
Record Linkage ◽  
Fault Tolerant ◽  
Source Code ◽  
Privacy Preserving ◽  
Third Party ◽  
Data Sets ◽  
Real World Data ◽  
Trusted Third Party ◽  
Record Keeping ◽  
Network Connection

Abstract Motivation Record Linkage has versatile applications in real-world data analysis contexts, where several data sets need to be linked on the record level in the absence of any exact identifier connecting related records. An example are medical databases of patients, spread across institutions, that have to be linked on personally identifiable entries like name, date of birth or ZIP code. At the same time, privacy laws may prohibit the exchange of this personally identifiable information (PII) across institutional boundaries, ruling out the outsourcing of the record linkage task to a trusted third party. We propose to employ privacy-preserving record linkage (PPRL) techniques that prevent, to various degrees, the leakage of PII while still allowing for the linkage of related records. Results We develop a framework for fault-tolerant PPRL using secure multi-party computation with the medical record keeping software Mainzelliste as the data source. Our solution does not rely on any trusted third party and all PII is guaranteed to not leak under common cryptographic security assumptions. Benchmarks show the feasibility of our approach in realistic networking settings: linkage of a patient record against a database of 10.000 records can be done in 48s over a heavily delayed (100ms) network connection, or 3.9s with a low-latency connection. Availability and implementation The source code of the sMPC node is freely available on Github at https://github.com/medicalinformatics/SecureEpilinker subject to the AGPLv3 license. The source code of the modified Mainzelliste is available at https://github.com/medicalinformatics/MainzellisteSEL.

scholarly journals Accountable Metadata-Hiding Escrow: A Group Signature Case Study

2015 ◽  
Vol 2015 (2) ◽  
pp. 206-221 ◽  
Author(s):  
Markulf Kohlweiss ◽  
Ian Miers
Keyword(s):  
Third Party ◽  
Group Signature ◽  
Signature Scheme ◽  
New Approach ◽  
Encrypted Data ◽  
Trusted Third Party ◽  
Group Signatures ◽  
Private Data ◽  
Gain Access

Abstract A common approach to demands for lawful access to encrypted data is to allow a trusted third party (TTP) to gain access to private data. However, there is no way to verify that this trust is well placed as the TTP may open all messages indiscriminately. Moreover, existing approaches do not scale well when, in addition to the content of the conversation, one wishes to hide one’s identity. Given the importance of metadata this is a major problem. We propose a new approach in which users can retroactively verify cryptographically whether they were wiretapped. As a case study, we propose a new signature scheme that can act as an accountable replacement for group signatures, accountable forward and backward tracing signatures.

scholarly journals Federated Trusted Third Party as an Approach for Privacy Preserving Record Linkage in a Large Network of University Medicines in Pandemic Research

2021 ◽  
Author(s):  
Christopher Hampf ◽  
Martin Bialke ◽  
Hauke Hund ◽  
Christian Fegeler ◽  
Stefan Lang ◽  
...  
Keyword(s):  
Data Integration ◽  
Record Linkage ◽  
Privacy Preserving ◽  
Medical Data ◽  
Third Party ◽  
Bloom Filters ◽  
Large Network ◽  
Trusted Third Party ◽  
University Medicine ◽  
Expansion Stage

Abstract BackgroundThe Federal Ministry of Research and Education funded the Network of University Medicine for establishing an infrastructure for pandemic research. This includes the development of a COVID-19 Data Exchange Platform (CODEX) that provides standardised and harmonised data sets for COVID-19 research. Nearly all university hospitals in Germany are part of the project and transmit medical data from the local data integration centres to the CODEX platform. The medical data on a person that has been collected at several sites is to be made available on the CODEX platform in a merged form. To enable this, a federated trusted third party (fTTP) will be established, which will allow the pseudonymised merging of the medical data. The fTTP implements privacy preserving record linkage based on Bloom filters and assigns pseudonyms to enable re-pseudonymisation during data transfer to the CODEX platform.ResultsThe fTTP was implemented conceptually and technically. For this purpose, the processes that are necessary for data delivery were modelled. The resulting communication relationships were identified and corresponding interfaces were specified. These were developed according to the specifications in FHIR and validated with the help of external partners. Existing tools such as the identity management system E-PIX® were further developed accordingly so that sites can generate Bloom filters based on person identifying information. An extension for the comparison of Bloom filters was implemented for the federated trust third party. The correct implementation was shown in the form of a demonstrator and the connection of two data integration centres.ConclusionsThis article describes how the fTTP was modelled and implemented. In a first expansion stage, the fTTP was exemplarily connected through two sites and its functionality was demonstrated. Further expansion stages, which are already planned, have been technically specified and will be implemented in the future in order to also handle cases in which the privacy preserving record linkage achieves ambiguous results. The first expansion stage of the fTTP is available in the University Medicine network and will be connected by all participating sites in the ongoing test phase.

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