# Trusted Academic Transcripts on the Blockchain: A Systematic Literature Review
## 2 Literature Background  
Blockchain, comprised of peer-to-peer networking, proof-of-work, and cryptography, is one of the technologies proposed by a man or a group of people under the pseudonym [PERSON] [38] to launch Bitcoin (the first proposed cryptocurrency) [39]. The system was meant to (finally) solve: (i) the double-spending problem, which allows for the owner of a currency or resource to spend currency at two different nodes simultaneously; and (ii) the problem of single points of failure. Blockchain and a consensus mechanism (briefly discussed below) provide solutions required to overcome these problems [40]. Prior to the solutions proposed by [PERSON] [38], no known application had been proposed to solve the double-spend problem in a decentralized manner. In order for the network to maintain consistency of the ledger, data are added by one node at a time (as otherwise, two different versions of the ledger would exist). Therefore, the system needed a method to decide (in a decentralized manner) which node will add data and when. Proof-of-Work (PoW) finally provided a solution to this [41]. Each node in the network will be trying to solve a computational problem, and the only way to solve the problem is to \"brute-force\" the answer. More specifically [42], the problem is to find a number x such that the hash of the number and the data being added to the ledger is less than d where d represents the current difficulty of the problem:  
\[\{x\in\mathbb{Z}\mid Hash(x+data)<difficulty\}\]  
The first node to find a number \(x\) that satisfies the above is the node that will be allowed to add data to the ledger next. There is no way to find an answer except for looping through all numbers until the problem is satisfied. Looping through all the numbers and computing the resultant hash requires time. So, the above provides: (i) a means of ensuring a \"random\" node is selected to add data next; and (ii) that data is added at a (rough) amount of time regulated by the difficulty value. In the case of Bitcoin this time, which is referred to as \"block time\" is around 10 min (whilst Ethereum for example provides a 10-s block time). This process is referred to as mining (in proof-of-work based systems) [39]. Among the underlying Bitcoin technologies, blockchain is the one that generated the most hype [43]. As can also be deduced from above, its motives were to provide immutability, transparency, and trustworthiness to the distributed ledger [44]. It was soon after realized that these characteristics were not only useful for cryptocurrencies, so an increasing number of blockchain-based applications have been developed [45]. [PERSON] et al. [46] describe the development of blockchain applications in three stages. The first stage mainly concerns ways to improve and simplify currency-based transactions [47]. Blockchain 2.0, on the other hand, aimed at decentralizing markets also by allowing transacting real-world assets through smart contracts and eliminating the needs of third parties [48; 49]. Finally, Blockchain 3.0 is sought to disrupt entire sectors such as healthcare, education, and science [50]. In the academic administration sector, blockchain applications are still in their infancy and are mostly used to validate students' achievements or share academic certificates [10]. In this context, blockchain can provide a mechanism to ensure that certificates (including/excluding relevant information as required) can be uploaded, with guarantees that the information has not been altered. To be precise, the following can be guaranteed: (i) that the certificate or rather the information notarized to the blockchain has not been changed since its registration; (ii) that the certificate has been issued by the owner of the particular issuing wallet; and (iii) that the certificate are delivered to those who earned them. The main challenges that arise with such a solution are (i) how to verify that issuers are, who they claim to be, and (ii) that owners are those who earned the certificate.