# Implementation and Security Test of Zero-Knowledge Protocols on SSI Blockchain
## 2 Background
### Related Work
They are found in Article 9 of Law 39/2015, of 1 October 2015 on the Common Administrative Procedure of Public Administrations [20], and in Directive 1999/93/93/EC of the European Parliament and of the Council [21]. Directive 1999/93/EC is known as the Electronic Identification and Trust Services (eIDAS) Regulation. These regulations are studied in depth in order to identify whether an SSI system is compatible with them and with the National Security Scheme (ENS) [22] in order to comply with the requirements necessary to conform an information system in the Public Administration. The conclusion of this article would be that an SSI model would be compatible with the Spanish regulation, although it would need some small adjustments to comply with the eIDAS regulation. Because this article focuses on the legal aspects of the problem, no case of actual and functional use is proposed to create said SSI system. Other authors see the use of Self-Sovereign Identity as an opportunity to achieve improvements and upgrades in the industrial sector in order to increase performance. Following the concept of Industry 4.0, there is an attempt to implement novel technologies in the industry in IoT networks, which will add much more time to the life cycle of the machinery while ensuring higher safety standards. The work of some authors from the University of Aveiro in Portugal [23] addresses the issue of Self-Sovereign Identity in the industry environment to achieve competitive advantages over the rest. They believe that using IoT device networks managed with an SSI system would bring economic benefits, such as better risk management and increased productivity. However, their work is primarily focused on the private sector, and the technology is not being considered as a benchmark available to everyone in the society of the future. As for the literature on quantum blockchain and quantum signatures, the authors of [24] propose a new quantum Byzantine agreement protocol that leverages quantum digital signatures and the recursion method to achieve almost one-half fault-tolerance and unconditional security. The proposed protocol overcomes the one-third fault-tolerance bound of a classical Byzantine agreement and addresses the security loopholes of classical cryptography methods. The protocol also includes a consistency check between each pair of rounds to ensure the unforgeability and nonrepudiation throughout the whole process. The authors experimentally demonstrate the proposed protocol's effectiveness at achieving a three-party and five-party quantum consensus for a digital ledger, highlighting the potential of quantum blockchain and quantum consensus networks. [PERSON], [PERSON] et al. [25] propose a high-efficiency quantum digital signature (QDS) protocol that achieves integrity, authenticity, and non-repudiation of data with information-theoretical security. The protocol uses asymmetric quantum keys acquired via secret sharing, one-time universal2 hashing, and one-time pad, requiring only a 384-bit key to sign documents of up to \(2^{64}\) lengths with a security bound of \(10^{-19}\). The proposed protocol achieves a signature efficiency that is more than \(10^{8}\) times higher than previous QDS protocols when signing a one-megabit document. The authors also build the first all-in-one quantum secure network integrating information theoretically secure communication, digital signatures, secret sharing, and conference key agreement, and experimentally demonstrate this signature efficiency advantage. However, the limitations of the proposed protocol need to be explored further, and its implementation in practical scenarios needs to be evaluated. Table 4 resumes related work. The present work aims to improve or expand the aforementioned works in the following aspects:  
* Greater transparency and clarity for the non-expert user who is interested in learning about ZKP protocols. * A more practical application that allows the user not only to understand the theory, but also to see it in operation and perform their own tests.