Revisiting cycles of pairing-friendly elliptic curves

A recent area of interest in cryptography is recursive composition of proof systems. One of the approaches to make recursive composition efficient involves cycles of pairing-friendly elliptic curves of prime order. However, known constructions have very low embedding degrees. This entails large parameter sizes, which makes the overall system inefficient. In this paper, we explore $2$-cycles composed of curves from families parameterized by polynomials, and show that such cycles do not exist unless a strong condition holds. As a consequence, we prove that no $2$-cycles can arise from the known families, except for those cycles already known. Additionally, we show some general properties about cycles, and provide a detailed computation on the density of pairing-friendly cycles among all cycles

DEFS - Data exchange with Free Sample Protocol

Distrust between data providers and data consumers is one of the main obstacles hampering digital-data commerce to take off. Data providers want to get paid for what they offer, while data consumers want to know exactly what are they paying for before actually paying for it. In this article, we present a protocol that overcomes this obstacle by building trust based on two main ideas. First, a probabilistic verification protocol, where some random samples of the real dataset are shown to buyers in order to allow them to make an assessment before committing any payment; and second a guaranteed, protected payment process, enforced with smart contracts on a public blockchain, that guarantees the payment of the data if and only if the data provided meets the agreed terms, and that refunds honest players otherwise.The architecture presented in this paper is supported and developed in the context of the i3-MARKET project [?]. The i3-MARKET project is an active European H2020 project focused on developing solutions for building an European data market economy by enhancing current marketplace platforms with innovative technologies (call H2020-ICT-2019-2 with grant agreement number 871754). This work is also supported by the TCO-RISEBLOCK (PID2019-110224RBI00), MINECO/FEDER funded project ARPASAT TEC2015-70197-R and by the Generalitat de Catalunya grant 2014-SGR-1504.Postprint (author's final draft

A protocol for data exchange with free samples using smart contracts

Distrust between data providers and data consumers is one of the main obstacles hampering digitaldata commerce to take off. Data providers want to get paid for what they offer, while data consumers want to know exactly what are they paying for before actually paying for it. In this paper, we summarize a protocol that overcomes this obstacle by building trust based on two main ideas. First, a probabilistic verification protocol, where some random samples of the real dataset are shown to buyers in order to allow them to make an assessment before committing any payment; and second a guaranteed, protected payment process, enforced with smart contracts on a public blockchain, that guarantees the payment of the data if and only if the data provided meets the agreed terms, and that refunds honest players otherwise.This research has been funded by i3Market (H2020- ICT-2019-2 grant number 871754). This work is also supported by the TCO-RISEBLOCK (PID2019-110224RBI00), ARPASAT (TEC2015-70197-R), Project RTI2018- 102112-B-I00 (AEI/FEDER,UE) and by the Generalitat de Catalunya grant 2014-SGR-1504Postprint (author's final draft

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

A Comprehensive study of arithmetic circuits and elliptic curves for efficient and scalable zero-knowledge proof systems

In recent years, zero-knowledge proofs have come to play a crucial role in distributed systems where there is no trust between the parties involved. Most popular proof systems are for the NP-complete language of arithmetic circuit satisfiability. Although there have been tremendous efforts in understanding, developing, and improving zero-knowledge proof systems, not much work has been done towards the study of arithmetic circuits. In this thesis, we contribute to this matter in three different aspects. First, we present circom, a programming language for writing arithmetic circuits that abstracts the complexity of the proof system. Second, we provide a deterministic algorithm for generating twisted Edwards elliptic curves that can be used to prove elliptic-curve cryptography statements in zero knowledge efficiently. Finally, we explore recursive composition of pairing-based proof systems with native circuit arithmetic, delving into the study of cycles of pairing-friendly elliptic curves of prime order.En els últims anys, les proves de coneixement zero han passat a tenir un paper crucial en el sistemes distribuïts on no hi ha confiança entre els participants. Els sistemes de prova més populars són pel llenguatge NP complet de satisfacibilitat de circuits aritmètics. Tot i que hi ha hagut molts esforços per entendre i millorar les proves de coneixement zero, no s’ha avançat tant en l’estudi dels circuits aritmètics. En aquesta tesi, contribuïm a aquest tema en tres aspectes. Primerament, presentem circom, un llenguatge de programació per escriure circuits aritmètics que abstreu la complexitat del sistema de prova. Segonament, proporcionem un algorisme determinista per a generar corbes el·líptiques que permeten demostrar eficientment declaracions de criptografia de corba el·líptica. Finalment, explorem la composició recursiva de sistemes de prova basats en aparellaments utilitzant l’aritmètica nativa dels circuits, aprofundint en l’estudi de cicles de corbes el·líptiques d’ordre primer amb aparellaments adients.Programa de Doctorat en Tecnologies de la Informació i les Comunicacion

Twisted Edwards elliptic curves for zero-knowledge circuits

Circuit-based zero-knowledge proofs have arose as a solution to the implementation of privacy in blockchain applications, and to current scalability problems that blockchains suffer from. The most efficient circuit-based zero-knowledge proofs use a pairing-friendly elliptic curve to generate and validate proofs. In particular, the circuits are built connecting wires that carry elements from a large prime field, whose order is determined by the number of elements of the pairing-friendly elliptic curve. In this context, it is important to generate an inner curve using this field, because it allows to create circuits that can verify public-key cryptography primitives, such as digital signatures and encryption schemes. To this purpose, in this article, we present a deterministic algorithm for generating twisted Edwards elliptic curves defined over a given prime field. We also provide an algorithm for checking the resilience of this type of curve against most common security attacks. Additionally, we use our algorithms to generate Baby Jubjub, a curve that can be used to implement elliptic-curve cryptography in circuits that can be validated in the Ethereum blockchain.This research has been partially funded by the projects Project RTI2018-102112-B-100 (AEI/FEDER, UE), i3Market (H2020-ICT-2019-2 grant number 871754) and TCO-RISEBLOCK (PID2019- 110224RB-I00)

New privacy practices for blockchain software

© 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The benefits of blockchain technologies for industrial applications are unquestionable. However, it is a considerable challenge to use a transparent system like blockchain and at the same time provide privacy to sensitive data. Privacy technologies permit conducting private transactions about sensitive data over transparent networks, but their inherent complexity has been overwhelming for many developers. Closing the gap between developers and privacy-preserving technologies would help to the full adoption of the privacy by design framework for blockchain software. To this end, in this paper we present the software tools we have implemented to bring complex privacy technologies closer to developers and facilitate the job of implementing privacy-enabled blockchain applications.This research is supported by the Ethereum Foundation Ecosystem Support [9], TCO-RISEBLOCK (PID2019-110224RB-I00), H2020-i3-MARKET, ARPASAT (TEC2015-70197-R), 2014-SGR-1504, RTI2018-102112-B-I00 (AEI/FEDER,UE) and H2020 PRESENT (856879).Peer ReviewedPostprint (published version