# Trusted Academic Transcripts on the Blockchain: A Systematic Literature Review
## 2 Literature Background
The latter can typically be resolved following a digital verification process using the wallet key. On the other hand, ensuring the authenticity of the issuing entity is a cumbersome task. Although some solutions were proposed (e.g., disclosure of institution public key), none have been widely accepted. Recent research by [PERSON] and [PERSON] [34] shows, however, that interest in this sector has spread globally, with prototypes and experiments taking place in many universities, academies, and professional schools. The most popular platforms, which are also at an advanced stage, are the following:  
**Blockcerts**: The first blockchain application developed by the Massachusetts Institute of Technology (MIT) to store and share digital diplomas and certificates. Built-in 2016, it allowed any entity to generate digital certificates for \"free\" [51]. An essential feature of this application is that it is blockchain agnostic. Blockcerts is, in fact, the application built \"on-top\" of a blockchain and can work with Bitcoin as well as Ethereum or Hyperledger. This system's known limitations are that it does not allow for the upload of documents in bulk and has no well-developed revocation system [52]. **Blockc.co**: Developed by the University of Nicosia [17], similar to Blockcerts, it also serves as a system to upload certificates on a blockchain. The advantage of using Block.co lies mainly in its cost reduction since it allows to upload multiple documents on the blockchain that will be hashed together. Criticized by [PERSON] et al. [51], this approach compromises privacy and access to the documents since the same hash points to multiple records. **BTCerts**: This is an initiative of the University of Birmingham, UK, also inspired by Blockcerts. The approach proposes to solve some of the weaknesses found in the MIT solution, such as revocation. BTCert proposes identifying a revoked certificate, querying the address embedded in the digital diploma, and checking if there is a change in the previous transaction outputs using the revocation address [53]. **EduCTX**: It is a platform born to digitalize the European Credit Transfer and Accumulation System (ECTS). This platform is used to control and transact a native token of the ECTX as academic credits [54]. While institutions have their own EduCTX address [35], students and organizations/employers are instead users of the platform. The project was started using the open-source blockchain Ark, operating on a consortium-type network. The advantage of using this platform lies in the multi-signature authorization process, which requires issuer and receiver approval to authorize an operation [52]. Technically speaking, applications involving real-world assets such as academic transcripts have different characteristics from those concerning cryptocurrencies [55]. Transparency to users is, of course, not guaranteed in private blockchains, which by definition denies access to non-authorized users. Immutability, on the other hand, is a peculiar feature of the Bitcoin blockchain, which unlike some other blockchain (that were altered as a result of a successful attack) has never been manipulated or modified [56]. Attacks are indeed possible given adequate resources but are highly improbable on large networks such as bitcoin [57]. Nevertheless, the main difference between a cryptocurrency transaction and a real-world one lies in the communication channel between the platform and the external world [58]. Since blockchains are blind to the real-world, information pertaining to assets such as food, stocks, natural resources, drugs, and documents need to be fed into the blockchain by trusted third parties known as oracles. Unlike blockchains, which are decentralized and trustless, oracles are centralized and trusted [59].