인증 프로세스는 사용자가 합법적인지 확인하는 데 사용되어야 하는 주요 단계이며, 사용자가 합법적인 사용자인지 확인하고 해당 사용자에게만 액세스 권한을 부여하는 데 사용되어야 한다. 최근에는 로그인 프로세스에 보안계층을 추가하여 인증에 하나의 요소만 사용하는 취약점을 해결하기 위해 대부분의 애플리케이션에서는 이중인증과 OTP 체계를 사용하고 있지만, 이 방법도 허가 없이 사용자 계정에 액세스할 수 있는 방법이 알려져 보안에 취약하다. 본 논문에서는 최소한의 개인정보만을 노출 조건으로 사용자를 인증하는 블록체인의 Smart Contract 기반으로 영지식(ZKP:Zero Knowledge Proofs)개인정보 인증 기법을 구현한다. 이는 블록체인 기술을 기반으로 인증프로세스에 많은 보안 기술을 제공하고, 개인정보 인증을 기존의 인증방식보다 빠르고 안전하게 수행할 수 있다.
We study the problem of simultaneously addressing both ballot stuffing and participation privacy for pollsite voting systems. Ballot stuffing is the attack where fake ballots (not cast by any eligible voter) are inserted into the system. Participation privacy is about hiding which eligible voters have actually cast their vote. So far, the combination of ballot stuffing and participation privacy has been mostly studied for internet voting, where voters are assumed to own trusted computing devices. Such approaches are inapplicable to pollsite voting where voters typically vote bare handed. We present an eligibility audit protocol to detect ballot stuffing in pollsite voting protocols. This is done while protecting participation privacy from a remote observer - one who does not physically observe voters during voting. Our protocol can be instantiated as an additional layer on top of most existing pollsite E2E-V voting protocols. To achieve our guarantees, we develop an efficient zero-knowledge proof (ZKP), that, given a value $v$ and a set $Φ$ of commitments, proves $v$ is committed by some commitment in $Φ$, without revealing which one. We call this a ZKP of reverse set membership because of its relationship to the popular ZKPs of set membership. This ZKP may be of independent interest.
Sensitive data have to be communicated via secure channels generally set up by using cryptography. This needs an authentic key exchange, which in turn requires an authentication process. However, the Internet of Things (IoT) includes its own challenges and security requirements. This paper introduces a novel signature algorithm and handshake protocol combining a zero-knowledge proof method being based on the graph isomorphism problem with an identity-based scheme to provide authentication with integrated key exchange while meeting the IoT challenges and security requirements. Our approach applies a way to parallelly perform multiple rounds usually needed by zero-knowledge proofs while retaining the same security level. Moreover, we present a graph compression algorithm providing a compression ratio of up to ca. 7:1. Our handshake protocol is resistant to active man in the middle attacks and does not require any public data pre-distribution or secret pre-sharing. Additionally, no third party has to hold any device-specific authentication data. Furthermore, our approach is application-independent and does not require any additional components or procedures. This paper also evaluates the high performance of our approach with regard to multiple affecting factors.
Miguel Díaz Montiel, Rachid Guerraoui, Pierre-Louis Roman
Blockchain intercommunication systems enable the exchanges of messages between blockchains. This interoperability promotes innovation, unlocks liquidity and access to assets. However, blockchains are isolated systems that originally were not designed for interoperability. This makes cross-chain communication, or bridges for short, insecure by nature. More precisely, cross-chain systems face security challenges in terms of selfish rational players such as maximal extractable value (MEV) and censorship. We propose to solve these challenges using zero knowledge proofs (ZKPs) for cross-chain communication. Securing cross-chain communication is remarkably more complex than securing single-chain events as such a system must preserve user security against both on- and off-chain analysis. To achieve this goal, we propose the following pair of contributions: the DACT protocol and the SurferMonkey infrastructure that supports the DACT protocol. The DACT protocol is a global solution for the anonymity and security challenges of agnostic blockchain intercommunication. DACT breaks on- and off-chain analysis thanks to the use of ZKPs. SurferMonkey is a decentralized infrastructure that implements DACT in practice. Since SurferMonkey works at the blockchain application layer, any decentralized application (dApp) can use SurferMonkey to send any type of message to a dApp on another blockchain. With SurferMonkey, users can neither be censored nor be exposed to MEV. By applying decentralized proactive security, we obtain resilience against selfish rational players, and raise the security bar against cyberattacks. We have implemented a proof of concept (PoC) of SurferMonkey by reverse engineering Tornado Cash and by applying IDEN3 ZKP circuits. SurferMonkey enables new usecases, ranging from anonymous voting and gaming, to a new phase of anonymous decentralized finance (aDeFi).
Daniël Reijsbergen, Aung Htein Maw, Zheng Yang, Tien Tuan Anh Dinh · 5 authors
Users today expect more security from services that handle their data. In addition to traditional data privacy and integrity requirements, they expect transparency, i.e., that the service's processing of the data is verifiable by users and trusted auditors. Our goal is to build a multi-user system that provides data privacy, integrity, and transparency for a large number of operations, while achieving practical performance. To this end, we first identify the limitations of existing approaches that use authenticated data structures. We find that they fall into two categories: 1) those that hide each user's data from other users, but have a limited range of verifiable operations (e.g., CONIKS, Merkle2, and Proofs of Liabilities), and 2) those that support a wide range of verifiable operations, but make all data publicly visible (e.g., IntegriDB and FalconDB). We then present TAP to address the above limitations. The key component of TAP is a novel tree data structure that supports efficient result verification, and relies on independent audits that use zero-knowledge range proofs to show that the tree is constructed correctly without revealing user data. TAP supports a broad range of verifiable operations, including quantiles and sample standard deviations. We conduct a comprehensive evaluation of TAP, and compare it against two state-of-the-art baselines, namely IntegriDB and Merkle2, showing that the system is practical at scale.
Panagiotis Michalopoulos, James Meijers, Srisht Fateh Singh, Andreas Veneris
Inter-vehicle communications can enable a wide array of novel applications that improve transportation safety and efficiency. However, due to the adversarial environment in which vehicles may operate, it is important to ensure information integrity. To achieve this, we present a blockchain-based reputation mechanism that allows participants to assess the trustworthiness of the received data based on the existing reputation score of the sender. After each data exchange, the receiver rates the sender by uploading an evaluation to the blockchain. To ensure that no tracking of the participants is possible, despite the open nature of the blockchain, we propose an address rotation scheme based on Zero Knowledge Proofs. Vehicles have the capability to change their blockchain address at regular intervals, while at the same time keeping their reputation score. Finally, we conduct experiments and simulations to evaluate our proposed system. The obtained results show that information integrity is ensured even in the presence of large number of adversaries and that privacy protection can be achieved at a reasonable cost.
This article seeks to discuss the opportunity for security enhancement in the Ethereum blockchain by introducing AI into the Ethereum blockchain ecosystem. Integrating AI with blockchain includes revolutionary approaches to protecting transactions by using techniques like anomaly detection, fraud, and predictive analysis. Hopwood et al. provide a background to blockchain technology with much focus on security in decentralized networks, especially Ethereum. It explores the basics of blockchain security based on cryptographic techniques, consensus algorithms, and the weaknesses of smart contracts. The discussion then turns to opportunities for AI technologies in blockchain security and the example of how the technologies can identify and prevent various activities. The most elaborate part of the paper is the Sequencer Level Security (SLS) protocol, a relatively new one that offers an improved model of transaction security that isolates the undesirable ones. The rollups and Layer 2 solutions involve the presented case of the Zircuit prototype and the implementation of SLS. The paper also discusses how AI may enhance personal data protection in blockchain environments via methods such as decentralized identity and zero-knowledge proofs. Legal and ethical issues are discussed with reference to data protection laws, including GDPR and CPRA, and their effects on the incorporation of AI and blockchain systems. Finally, it envisions the future trends, issues, and opportunities of AI and blockchain security based on a suggested research agenda. Based on this all-around assessment, AI plays a pivotal part in enhancing the security and privacy of Ethereum blocks.
As the basic problem that introduces the idea of secure multi-party computation (SMC), millionaires’ problem (MP) is one of the research highlights in the field of SMC. However, most of current protocols for MP are only secure in semi-honest model, which using public key cryptography schemes, and there are few secure schemes in malicious model exist security defects. Therefore, this paper analyzes the Li et al.’s protocol for MP that secure in malicious model. Firstly, we point out several behaviours that can be successfully implemented in Li et al.’s protocol. Secondly, by using the zero-knowledge proof (ZKP) for the equality of discrete logarithm (DL), cut-and-choose method etc. We propose the improved protocol and show how to detect malicious behaviours. Finally, we analyze the correctness and security against malicious behaviours of the improved protocol.
A number of arithmetization-oriented ciphers emerge for use in advanced cryptographic protocols such as secure multi-party computation (MPC), fully homomorphic en-cryption (FHE) and zero-knowledge proofs (ZK) in recent years. The standard block ciphers like AES and the hash functions SHA2/SHA3 are proved to be efficient in software and hardware but not optimal to use in this field, for this reason, new kind of cryptographic primitives were proposed recently. However, unlike traditional ones, there is no standard approach to design and analyze such block ciphers and the hash functions, therefore their security analysis needs to be done carefully. In 2018, StarkWare launched a public STARK-Friendly Hash (SFH) Challenge to select an efficient and secure hash function to be used within ZK-STARKs, transparent and post-quantum secure proof systems. The block cipher JARVIS is one of the first ciphers designed for STARK applications but, shortly after its publication, the cipher has been shown vulnerable to Gröbner basis attack. This paper aims to describe a Gröbner basis attack on new block ciphers, MiMC, GMiMCerfand the variants of JARVIS. We present the complexity of Gröbner basis attack on JARVIS-like ciphers. Then we give results from our experiments for the attack on reduced-round MiMC and a structure we found in the Gröbner basis attack for GMiMCerf•
Our proposed scheme is modified from that of Camenisch et al., yet achieves more efficient than their scheme. In general, a batch verification method is more advantageous and is also able to save more cost than the original scheme, while non-interactive zero knowledge proof requires fewer communication rounds than interactive zero knowledge proof. The proposed scheme employs the simplified small exponents test method for secure and fast batch verification on multiple signature elements, which can remarkably reduce the number of time-consuming pairing operations required by both a prover and a verifier, resulting in greatly improved computational efficiency. By applying non-interactive zero knowledge proof technique, the proposed scheme also decreases the number of communication rounds required between both of them.
Abstract Aiming at the node security risks and key management vulnerabilities in heterogeneous sensor networks, a key management protocol for heterogeneous sensor networks based on zero-trust security and chaotic neural networks (KMPHSN-ZTSCNN) was proposed. Based on the singular matrix decomposition of difficulty and Hopfield overload chaos neural network classification features, using blockchain and zero-knowledge proof to realize sensor network node registration and authentication, it relies on channel state information (CSI) and adjustable mathematical function to generate dynamically changing keys to complete continuous verification and achieve zero-trust security authentication to ensure data security. The protocol can dynamically allocate different keyspace sizes according to the security level of the group, node storage capacity and computing capacity, and can adapt to the asymmetric structure of heterogeneous sensor networks. Theoretical proof and experimental performance analysis show that the protocol is feasible and can meet the security requirements of heterogeneous sensor networks.
The integration of the Internet of Things (IoT) with traditional healthcare systems has improved quality of healthcare services. However, the wearable devices and sensors used in Healthcare System (HS) continuously monitor and transmit data to the nearby devices or servers using an unsecured open channel. This connectivity between IoT devices and servers improves operational efficiency, but it also gives a lot of room for attackers to launch various cyber-attacks that can put patients under critical surveillance in jeopardy. In this article, a Blockchain-orchestrated Deep learning approach for Secure Data Transmission in IoT-enabled healthcare system hereafter referred to as “BDSDT” is designed. Specifically, first a novel scalable blockchain architecture is proposed to ensure data integrity and secure data transmission by leveraging Zero Knowledge Proof (ZKP) mechanism. Then, BDSDT integrates with the off-chain storage InterPlanetary File System (IPFS) to address difficulties with data storage costs and with an Ethereum smart contract to address data security issues. The authenticated data is further used to design a deep learning architecture to detect intrusion in HS network. The latter combines Deep Sparse AutoEncoder (DSAE) with Bidirectional Long Short-Term Memory (BiLSTM) to design an effective intrusion detection system. Experiments on two public data sources (CICIDS-2017 and ToN-IoT) reveal that the proposed BDSDT outperformed state-of-the-arts in both non-blockchain and blockchain settings and have obtained accuracy close to 99% using both datasets.
Daniel Kang, Tatsunori Hashimoto, Ion Stoica, Yi Sun
As ML models have increased in capabilities and accuracy, so has the complexity of their deployments. Increasingly, ML model consumers are turning to service providers to serve the ML models in the ML-as-a-service (MLaaS) paradigm. As MLaaS proliferates, a critical requirement emerges: how can model consumers verify that the correct predictions were served, in the face of malicious, lazy, or buggy service providers? In this work, we present the first practical ImageNet-scale method to verify ML model inference non-interactively, i.e., after the inference has been done. To do so, we leverage recent developments in ZK-SNARKs (zero-knowledge succinct non-interactive argument of knowledge), a form of zero-knowledge proofs. ZK-SNARKs allows us to verify ML model execution non-interactively and with only standard cryptographic hardness assumptions. In particular, we provide the first ZK-SNARK proof of valid inference for a full resolution ImageNet model, achieving 79\% top-5 accuracy. We further use these ZK-SNARKs to design protocols to verify ML model execution in a variety of scenarios, including for verifying MLaaS predictions, verifying MLaaS model accuracy, and using ML models for trustless retrieval. Together, our results show that ZK-SNARKs have the promise to make verified ML model inference practical.
Climate change will widen health inequities; action on the social determinants of health is essential In a conversation recently, a former senior public servant suggested to me that the social determinants of health are too theoretical. It is true that there are a number of theoretical perspectives associated with social determinants. A key one, from Nobel Laureate Amartya Sen,1 highlights the importance of having the freedoms and capabilities to lead a flourishing life. According to theory, these are shaped by the conditions in which people are born, live, work and age, which are unequally distributed.2 There is, however, nothing theoretical about the manifestation of social inequities and their impact on peoples’ health. Every day, people living in Australia embody stark inequities in income, working conditions, lived environment, and access to quality health and social care. For example, before the coronavirus disease 2019 (COVID-19) pandemic, Australians in the top 20% income bracket received six times more money than the lowest 20%.3 Three million Australians were estimated to be living below the poverty line in 2017, including 18% of all children.3 Before the pandemic, more than a million people were in rental stress, and waiting lists for social housing were into the hundreds of thousands.4 Within the first few months of 2020, 880 000 Australians lost their jobs, with women, young people, and those in precarious employment disproportionally affected.3 Workers in casual employment accounted for 63% of job losses between February and May 2020.3 Since the COVID-19 pandemic began, Australia’s 31 billionaires have increased their wealth by $85 billion.5 People embody these inequities,6 which makes them sick and contributes to high levels of premature death. In 2017, 17% of Victorians reported high psychological distress. In 2020, that rose to 44% and to 60% among those who lost their jobs.7 Across Australia, people living in the lowest socio-economic quintile had mortality rates twice as high as those in the highest quintile, and these inequities widened between 2011 and 2016.8 Despite narrowing, the gap in life expectancy between Indigenous and non-Indigenous Australians remains high.9 What do social determinants have to do with climate change and planetary health? The fires, hail, floods and droughts that Australia has endured in recent years10 affect everyone, but not everyone experiences them equally.11 Affluent people can afford to live in insulated buildings with air conditioning and air purifiers, or add flood proofing and extra drainage. Meanwhile, people who are poor, older individuals, people with disabilities, and those who are socially marginalised are the least able to adapt to the changing climate, unable to escape the fires and heat, and live in dwellings and environments that amplify its effects.11 As has happened in other countries experiencing similar impacts from climate change, having lost homes and livelihoods, and fearful for the future, some people may leave their communities and perhaps the country.12 This will exacerbate inequities, with those who have more financial and social capital having more options — wealthy Australians are already buying land in Tasmania to escape the worst ravages of climate change.13 For people living in caravan parks in Lismore, New South Wales, having insurance is a stretch.13 Moving is not an option. This climate change-exacerbated social inequity adds to existing inequities in disease burdens and premature mortality — this is climate change interacting with the social determinants of health inequities.11 Planetary health inequity is a concept that recognises the impact of climate change on social and health inequities. It also recognises the importance for health equity of considering planetary systems — if we do not have a functioning Earth system, we have social disruption and risk to human survival. Planetary health inequity therefore embodies the common drivers of climate change and health inequity. These common drivers comprise major structural forces. Power asymmetries between actors, institutions and ideas, a neoliberal fetishism of market forces and individualism, hyperglobalisation, and the associated norms and values that permeate institutions and communities affect policy decisions that structure society and differentially affect daily living conditions and, ultimately, health.14-18 These structural social determinants of health inequity overlap substantially with the drivers of climate change and can be described collectively as the global “consumptogenic system”. The consumptogenic system is characterised by institutions, policies, business practices, and social norms that embed and entrench principles of extractive capitalism and colonialism.19 Such a system encourages and rewards excessive production and hyperconsumerism of fossil fuel-reliant goods and services that are unhealthy and inequitably valued and distributed.20 If left on the current trajectory, the consumptogenic system will amplify potentially irreversible consequences for environmental degradation, inequalities and poor health. Governments have the chance to advance planetary health equity goals by addressing the consumptogenic system and inequitable distribution of resources that create negative health outcomes and climate change. The issue is not that it is too theoretical, the issue is the often lack of political will to address inequality, adopt a social model of health, and tackle climate change. In the May 2022 federal election, the Australian electorate demanded change. Encouragingly, the new Labor government promised to do better by the people and, although not in the language of the social determinants, their proposed action plan21 will go some of the way to advance planetary health equity goals. But it must go further. Achieving the transformative goal of planetary health equity requires a “social vaccine”22 (Box), the targets of which are the conditions underpinning four basic requirements for health and equity to flourish: a life with security, opportunities that are fair, a planet that is habitable by humans and supports biodiversity, and governance that is just. Achieving these conditions requires the ambition, design and implementation of policies that ensure a fair social foundation and economic environment operating within the ecological ceiling.23 In Australia, as elsewhere, we have long needed policy that helps with adaptation to the damage already done by climate change. Good social and planning policy that ensures access to safe, stable and affordable housing, decent working conditions for all, income support levels that enable living with dignity, and inclusive infrastructure development is good climate adaptation policy. They are also good health equity policies. Adaptation is essential. So too is mitigation. The Climate Change Bill 2022 commits Australia to a greenhouse gas emissions reduction target of a 43% reduction from 2005 levels by 2030. This target should be considered only a starting point. A roadmap to net zero and an empowered secure Climate Change Authority is essential. Adequate climate change mitigation and planetary health equity will not be achieved unless there is ambitious and immediate action that disrupts the consumptogenic system. The targets should be the institutions, actors, structures and discourses that embed, facilitate and normalise the global dominance of a consumptogenic system addicted to growth regardless of the environmental, social and health costs. At the very least, any new fossil fuel project must be assessed for potential damage to species and environments through its impacts on climate change. Fundamentally, however, disruption of this system requires Australia and the rest of the world to stop extracting, burning and investing in oil, coal, gas and other fossil fuels, with government vetoing all new fossil fuel developments. The absence of an overarching framework guiding the actions of all Australian Government departments in a mission towards planetary health equity is problematic. This lack of authorising environment enables at best an ineffective siloed, scattergun approach; at worst policy silence. Implementing a national strategy that brings together climate change, inequality and health, such as the proposed Climate and Health Alliance’s Healthy, Regenerative and Just framework, is essential.24 An engaged strong civil society is key to the delivery of a social vaccine. Implementing a progressive policy framework will confront stubborn resistance and challenge the power of dominant vested interests. Public-interest coalitions can support governments to act, as well as hold them to account.25 Climate change and health alliances are essential — doctors and other health professionals have knowledge, opportunity and political leverage that can help ensure actions are taken.24 This article has laid out ways of advancing planetary health equity goals. To help achieve these, the health community must advocate for and engage in intersectoral policy discussions relating to the social determinants and the structural consumptogenic system. Acting immediately on these issues is critically important if we are to avert a planetary health inequity crisis. No relevant disclosures. Commissioned; externally peer reviewed. Open access publishing facilitated by Australian National University, as part of the Wiley - Australian National University agreement via the Council of Australian University Librarians.
Abstract With the the advent era of big data, the secure computation calculates data on the premise of protecting data privacy, to realize the availability and invisibility of data. Secure multi-party computation, as one of three major technical tools of privacy computing, can still securely carry out data collaborative computation without a trusted third party. As an important branch of secure multi-party computation, the secure computing geometric problem can solve practical problems in the military, national defense, finance, life, and other fields, which has important research significance. In this paper, the graphic similarity problem is studied. Firstly, this paper proposes the adjacency matrix vector coding method of isomorphic graphics and uses the Paillier variant cryptosystem to securely solve the graphic similarity judgment under the semi-honest model. By using an elliptic curve cryptosystem and zero-knowledge proof to solve the possible malicious attacks under the semi-honest model, a graphic similarity judgment protocol under the malicious model is designed. The protocol can resist malicious attacks, has high computational efficiency, and has wide application value.
A major issue for many applications of blockchain technology is the tension between immutability and compliance to regulations. For instance, the GDPR in the EU requires to guarantee, under some circumstances, the right to be forgotten. This could imply that at some point one might be forced to delete some data from a locally stored blockchain, therefore irreparably hurting the security and transparency of such decentralized platforms. Motivated by such data protection and consistency issues, in this work we design and implement a mechanism for securely deleting data from Bitcoin blockchain. We use zero-knowledge proofs to allow any node to delete some data from Bitcoin transactions, still preserving the public verifiability of the correctness of the spent and spendable coins. Moreover, we specifically use STARK proofs to exploit the transparency that they provide. Our solution, unlike previous approaches, avoids the complications of asking nodes to reach consensus on the content to delete. In particular, our design allows every node to delete some specific data without coordinating this decision with others. In our implementation, data removal can be performed (resp., verified) in minutes (resp., seconds) on a standard laptop rather than in days as required in previous designs based on consensus.
Privacy preservation is highly expected in the Bitcoin Network. However, only applying pseudonyms cannot completely ensure anonymity/unlinkability between payers and payees. Current approaches mainly depend on a mixer service, which obfuscates payer-payee relationships of transactions. While the mixer service improves transaction privacy, it still suffers from some severe security threats (e.g., DoS attack and collusion attack), and does not support effective and reliable off-chain payment in a parallel mode. In this article, we propose a mixing protocol for the Bitcoin Network based on zero-knowledge proof, called SofitMix. It is the first mixing protocol that can effectively resist both the DoS attack and the collusion attack. It can also support a set of parallel off-chain payments in a reliable way no matter whether some payers abort a transaction. We analyze and prove SofitMix security following the Universal Composability model with regard to fair exchange, unlinkability, collusion-resistance, DoS-resistance and Sybil-resistance. Through a proof-of-concept implementation, we demonstrate its validity and fairness. We also show its advance on off-chain payment reliability and DoS attack resistance, compared to TumbleBit.
The issue of identity authentication for online medical services has been one of the key focuses of the healthcare industry in recent years. Most healthcare organizations use centralized identity management systems (IDMs), which not only limit the interoperability of patient identities between institutions of healthcare, but also create isolation between data islands. The more important matter is that centralized IDMs may lead to privacy disclosure. Therefore, we propose Health-zkIDM, a decentralized identity authentication system based on zero-knowledge proof and blockchain technology, which allows patients to identify and verify their identities transparently and safely in different health fields and promotes the interaction between IDM providers and patients. The users in Health-zkIDM are uniquely identified by one ID registered. The zero-knowledge proof technology is deployed on the client, which provides the user with a proof of identity information and automatically verifies the user's identity after registration. We implemented chaincodes on the Fabric, including the upload of proof of identity information, identification, and verification functions. The experiences show that the performance of the Health-zkIDM system can achieve throughputs higher than 400 TPS in Caliper.
By the means of asymptotic security of cryptographic security mechanism we can get knowledge about efficiency and tolerable features against various type of attacks compromised on it. Analytical study about how zero-knowledge proofs can be used with Diffie Hellman problem (DHP) are presented in this research. One of the better algorithms of discrete logarithm problem which is suggested by Henry for zero knowledge proofs is suitable for DHP problem for the robustness analysis of it. The efficiency of discrete logarithm algorithm for DHP problem and integer factorization problem are analyzed and made comparison between them and covariance and correlation between their asymptotic functions is obtained as final result which clearly give us idea about strong relationship between each other and correlation factor between them is high, so they are similar in nature.
(English) Invoice factoring has been a popular way to provide cash flow for businesses. The primary function of a factoring system is to prevent an invoice from being factored twice. In order to prevent double factoring, many factoring ecosystems use one or several centralized entities to register factoring agreements. However, this puts a lot of power in the hands of these centralized entities and makes it difficult for users to dispute situations in which factoring data is unavailable, wrongly recorded or manipulated by negligence or on purpose. This thesis presents our research around the current problems of invoice factoring and our new solutions to solve this process using the blockchain technology. A public blockchain can keep a permanent, secure, ordered and transparent record of transactions which are then available for everyone at any time to view and verify. In this thesis, we start proposing a base solution, and we gradually enhance it. In the base protocol, we propose an architecture for invoicing registration based on a general blockchain. The blockchain platform builds trust between the parties by executing transactions correctly. We employed a smart contract to complete the registration process, and prevent double factoring. The smart contract provides for auditing and dispute resolution in such a way that privacy is protected and relevant information is always available. In the second protocol, we add a relayer to our architecture for easier on-boarding. Only the relayer is required to submit blockchain transactions, and pay the corresponding fees. Other participants can proxy their transactions through the relayer, and pay the relayer in fiat money. We also enhance our identity management and authentication using the concept of verifiable credentials (VC) in order to better comply with the Know-Your-Customer (KYC) regulation. In fact, in this architecture, participants use their decentralized identifiers (DIDs) and the DIDComm protocol for asynchronous and secure off-chain interactions. In the final protocol, we greatly enhance our smart contract with respect to the conditions it checks before registering an invoice factoring. We integrate non-interactive zero-knowledge proofs and cryptographic commitments into our solution. With these cryptographic tools in place, we can prevent a special type of denial of service (DoS) attack and better verify invoice details without compromising privacy. Our protocols are very efficient in terms of blockchain costs. In particular, we only need one transaction to register an invoice factoring, and most of the details are recorded in low-cost blockchain storage. Our evaluations and comparison with the literature reveals that our protocols are superior to the related works with respect to efficiency, security, privacy, and ease of use. (Català) La venda de factures o "invoice factoring" ha estat una forma popular de proporcionar flux de caixa a les empreses. La funció principal d'un sistema de venda de factures és evitar que una factura sigui venuda dues vegades. Per evitar la doble venda, molts ecosistemes de factoring utilitzen entitats centralitzades per registrar els acords de venda de factures. Això, però, posa molt poder en mans d'aquestes entitats centralitzades i dificulta que els usuaris puguin impugnar o rebatre situacions en què les dades de venda no estan disponibles, es registren erròniament o es manipulen ja sigui per negligència o a propòsit. Aquesta tesi presenta la nostra recerca al voltant dels problemes actuals dels sistemes de registre de venda de factures i les nostres novedosses solucions per resoldre aquest procés utilitzant la tecnologia "blockchain" (cadena de blocs). Mitjançant una blockchain pública es pot mantenir un registre permanent, segur, ordenat i transparent de transaccions que estan disponibles per a tothom en qualsevol moment per poder ser observades i verificades. A la tesi, comencem proposant una solució base i la anem ampliant i millorant gradualment. La primera proposta és un protocol que utilitza una arquitectura amb blockchain. La plataforma blockchain genera confiança entre les parts ja que garanteix la correcta execució de les transaccions. En aquest sentit, fem servir un contracte intel·ligent per completar el procés de registre i evitar la doble venda. El contracte intel·ligent permet l'auditoria i la resolució de disputes de manera que protegim la privadesa i fem que la informació rellevant estigui sempre disponible. Al segon protocol, afegim un "relay" o retransmissor a la nostra arquitectura per facilitar la incorporació d'usuaris al sistema. El retransmissor és l'únic que envia transaccions a la cadena de blocs i el que paga les taxes corresponents. Els altres participants poden delegar l'enviament de les seves transaccions al repetidor i pagar amb diners fiduciaris. En aquesta proposta també millorem la gestió de la identitat i de l'autenticació utilitzant el concepte de credencials verificables (Verifiable Credentials o VC) per complir millor amb la normativa "Conegui el seu client" (Know Your Customer o KYC). De fet, en aquesta arquitectura, els participants utilitzen els seus identificadors descentralitzats (Decentralized Identifier o DID) i el protocol DIDComm per a les interaccions asíncrones i segures fora de la cadena. Al protocol final, millorem en gran mesura el nostre contracte intel·ligent pel que fa a les condicions que comprova abans de registrar una venda de factura. En aquesta última solució, integrem proves no interactives de coneixement nul (Zero Knowledge Proofs o ZKP) i compromisos criptogràfics. Amb aquestes eines, podem evitar un tipus especial d'atac de denegació de servei (Denial of Service o DoS) i verificar millor els detalls de les factures sense comprometre la privadesa. Els nostres protocols són molt eficients en termes de cost per comissions. En particular, només necessitem una transacció per registrar una factura i la majoria dels detalls es registren a l'emmagatzematge de la cadena de blocs de baix cost. Les nostres avaluacions i la comparació amb la literatura revelen que els nostres protocols són superiors als treballs relacionats pel que fa a l'eficiència, la seguretat, la privadesa i facilitat d'ús.