## 5 Discussion  
The proposed framework is designed with the _privacy by design_ principle in mind to protect personal data and to comply with the European GDPR, one of the most restrictive regulations insofar privacy is concerned. By using this system, data subject's consent must be explicitly granted and registered as the holder transmits to the institution \(E\) their blockchain account to be associated with the issued academic information. After the educational data were issued by the institution, the holder of the data has the possibility to allow and later withdraw access to all or only certain data items to any  
Figure 11: The consortium blockchain and the private one to store academic information using IPFS. Figure 10: Consortium blockchain and its interconnection with the private ones. third party just by adding or removing their account (\(T\)'s) in a smart contract. Everything is trustfully and tamperproof recorded. The design allows extending how the information can be accessed. For example, if the holder \(H\) would like to share their academic records (or parts of them) using a nonpredictable URL in a web page (or using a QR code), and hence, anyone can check for the authenticity of the data without accessing directly to the blockchain, it could be easily performed. In this use case, only a web service (provided by any public or private company free or at cost) is necessary, whose blockchain associated account should be authorized by \(H\) in _SCAccess_, and therefore, access to the verification could be granted. In this scenario, there would not be an exact record of who accessed that URL since it would be publicly accessible. The only information accounted for would be that the web service requested access to the data. If the holder \(H\) or the institution \(E\) decides to cancel access to a third party by removing its account in _SCAccess_, it will receive a notification and should delete all the related information both online and offline. While institution \(E\) exists, a holder has the possibility to request all the information about them by just submitting all their associated blockchain accounts (different \(H\)s of the same holder) to comply with the portability requirement of the GDPR. The holder can find out who (and when) tried to access or even accessed their data just by querying the logs, as required by the GDPR. The right to be forgotten can be implemented by requesting the institution to erase all the recorded data about the holder. If this is legally feasible, the organization would delete the records from its local databases, tag the data as invalid in the blockchain and eliminate all the accounts in _SCAccess_ for that holder so the information cannot be accessed by anyone. Only nonpersonal information would remain in the blockchain since no academic data are ever stored in the blockchain. In case academic institution \(E\) disappears, all the associated academic information should be published in a private blockchain connected to an IPFS distributed file system so the holder of the educational data could have them verified and even recover them using the secret key. Under this scenario, if the holder \(H\) deletes their secret key, as the encrypted information is only stored on a private distributed storage with limited access, the \"right to be forgotten\" is preserved since the GDPR considers deleting the decrypting keys to be a valid option. The proposed model utilizes several blockchains to tackle scalability and performance issues since in the educational sector, there are data generation peaks in specific moments of the year (e.g., at the end of the term). With this solution, every private blockchain should be independently dimensioned to safely record all the transactions in a reasonable time and, later, transfer the data to the main consortium blockchain where transactions would be incorporated, but they do not need to be intensely analyzed since they come from a theoretically reliable source (a private blockchain).