## 1 Introduction
It comprehensively addresses personal rights in different scenarios, including rights of access to collected data, erasure, restriction of processing, to be notified on any personal data operation, portability of data, objection, or even rights related to automatic decision making and profiling and its limitations. It is important to remark that the regulation is applied to personal information such as name, age, etc. as well as to other data that, in combination with other means, can be used to identify a natural person. Infringements of the GDPR can lead to significant administrative fines. This research proposes a novel and innovative solution to issue, store, recover, share, and verify heterogeneous and unrestricted types of academic information using blockchain, a technology whose characteristics of resistance to unauthorized modifications and traceability of the operations carried out make it perfect to achieve the pursued objectives. Without changing proprietary information systems, the educational actors can generate and tamperproof register any type of educational data, both formal or informal, and send it to the holder automatically and securely whenever it is requested so the owner can transfer it to a third party who can seamlessly check for its authenticity. In this design, the holder of the academic data has the possibility to share all or only some parts of the issued information with the third party according to their interests. The system also contemplates that if for any reason, the academic institution disappears, under certain conditions, the issued academic accreditations could still be verified and even recovered by the holder. It is also important to remark that, as it will be later discussed, the existing blockchain-based initiatives to generate and validate academic data utilize diverse approaches to record the information, but they do not take into consideration the strict restrictions imposed by the General Data Protection Regulations (GDPR) in their design, they do not conveniently address the problem of scalability when an increasing number of documents is generated, or both. The proposed solution in this research, which complies with the restrictions imposed by the GDPR, addresses these requirements in an integral way by proposing a solution to face scalability problems when the volume of information is very high, especially strengthening the protection of personal data. To sum up, the main contributions of this research are as follows:  
* It analyzes the application of blockchain technologies to issue and verify educational data;
* It proposes an innovative model that supports the issuance, storage, and verification of different types of academic information under different scenarios that comply with the GDPR and tackles the scalability challenge present in almost every present blockchain initiative;* It performs a security analysis of the described model;
* It proposes an implementation of the model as a constructive proof of concept with the objective of confirming the feasibility of the designed framework using available state-of-the-art technologies. The rest of the paper is organized as follows: the main features of blockchain technology and its application in the educational sector and a comparison of related work to the proposed design in this research are introduced and described in Section 2. Then, Section 3 is devoted to introduce some features of the General Data Protection Regulation (GDPR) and to detail the conceptual design of the proposed solution. Section 4 proposes a proof-of-concept implementation with existing technology. Section 5 discusses the results of the proposed model. Finally, conclusions are drawn and future research perspectives are analyzed in Section 6.