# NFTs for the Issuance and Validation of Academic Information That Complies with the GDPR
## 2 Preliminaries  
### Blockchain and Education  
Blockchain, the technology behind Bitcoin [6], introduced in 2008, serves as a distributed and decentralized database capable of securely recording transactions in an immutable manner. Transactions within a blockchain are stored in blocks, each cryptographically linked to the preceding one, rendering the information nearly impossible to alter once registered in the blockchain. Simultaneously, it remains easily verifiable. Operating as a decentralized system, there are no central actors, and all processes are executed by nodes or devices comprising the peer-to-peer network in which blocks of information are shared. Actual block contents vary depending on the type of blockchain. They might solely represent economic transactions, as in Bitcoin, or register state changes in variables on platforms like Ethereum [7], enabling the execution of smart contracts [8]. These smart contracts operate autonomously based on their programming within the blockchain, reading information from one or multiple block transactions, and even modifying and storing data in a new block as a new transaction. Due to its foundations, blockchain holds the potential to establish verifiable and transparent records of information, such as academic data. There exist various types of blockchains, ranging from public blockchains like Bitcoin and Ethereum to private ones, like those based on the Hyperledger framework [9] and consortium blockchains. Public blockchains operate openly without permission (i.e., they are known as permissionless blockchains), allowing anyone to join, read, send, and add information. This transparency might be suitable for ensuring transparency in academic certificate issuance. However, the lack of trust among network members in public blockchains necessitates stricter security mechanisms, which can hinder transaction speed and volume compared to other blockchain types. Conversely, access to information in private blockchains requires permission, issued by the institution that created, deployed, and maintains the blockchain (i.e., they are known as permissioned blockchains). While offering increased trust among network teams, the security mechanisms need not be as stringent, enabling higher transaction speeds and volumes compared to public blockchains. Hyperledger is presently the most popular framework to create such blockchains. Consortium blockchains combine elements of both public and private blockchains. They require permission to join but may be configured to allow any user to access stored information, depending on the group of institutions maintaining the blockchain. Initially, private and consortium blockchains might seem preferable in educational settings, where greater data privacy management and control are necessary. However, this is not always the case [5; 10], due to other data protection aspects outlined in the General Data Protection Regulation (GDPR), one of the world's strictest data protection legislations. While blockchain in education could revolutionize certificate issuance and management by creating immutable and accessible records for validating academic achievements, its adoption must be carefully considered with respect to personal data protection and compliance with regulations like the GDPR. Existing research on blockchain's educational applications [11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30] commonly highlights certificate issuance and validation as the most frequent use case [12; 27], with other applications also present [28; 31].