# Notarization and Anti-Plagiarism: A New Blockchain Approach
## 4 Comparative Analysis
### Notarization Blockchain-Based Apps  
All the apps analyzed in this paper use the SHA-256 algorithm [31] for generating the hash of the file(s) to be notarized.  
The Noberasco app \"Opentimestamps\" [32] is a web-app based on the Bitcoin (BTC) blockchain [2; 3]. It is an app that allows you to put a \"time stamp\" on a file by selecting it and without uploading the file to the Noberasco servers. This is to preserve the privacy of users. The system returns a file to the user with \".ots\" extension that contains the proof of notarization. Noberasco also allows you to verify the date of existence of a file by uploading the previously returned file with \".ots\" extension and by selecting the original file that will not be uploaded to the server. It does not offer any other functionality.  
The \"BCH Notary\" app [33] allows you to attest to the ownership of a file, using the Bitcoin cash (BCH) blockchain [34] at a cost of 0.0002 BCH. In this app, you can only notarize and verify the ownership of a document by selecting it on local machine. The file will not be uploaded to their servers. It does not support any additional functionality.  
The \"Chainsign\" app [35] is based on the EOS blockchain [36; 37]. This app notarizes files for free. Chainsign locally calculates the hash of the file being notarized without uploading to a server. It is also possible to enter the web address of a file to be notarized.  
The hash algorithm used is SHA256. Chainsign does not offer further functionalities beyond those described above.  
The app called CERTO [38; 39] performs notarization of files using the NXT blockchain [40; 41] and the multichain platform \"Ardor\" [42; 43]. CERTO allows for notarization of individual files, and it is possible to also have the function of chain of custody. Finally, it is possible to obtain a notarization report in PDF format. No other functionality is supported.  
Quadrans Foundation [44] offers a free tool for notarizing files [45; 46], a centralized app based on the Quadrans blockchain [47]. The notarization process is entirely managed via email. Among the available features, there is the notarization of several files at the same time, but the user is asked to insert all the files to be notarized in a single archive. So, the entire archive is notarized and not the single file it contains. Furthermore, the notarization system offered by Quadrans Foundation uses a centralized archive server.  
Dedit [48; 49] propose a centralized app that uses the user browser to run the SHA256 algorithm to notarize files. Only the hash of the file, plus some metadata, are transmitted to Dedit's centralized server. The hash is recorded on the Algorand blockchain [50; 51; 52] with a timestamp. At the end of Dedit's notarization process, a PDF report is made available to the user. In addition, Dedit offers a file custody service (not P2P) with a free space available of 10 MB, a multiple digital signature service, and a file sharing service.  
In the table below, we made a check of the desirable features for each notarization app considered.  
As shown in Table 1, none of the notarization apps considered encapsulate all the desired features. In detail, even though all notarization apps analyzed allow you to notarize a file, none of the analyzed solutions offer P2P file custody services or a decentralized type of archive server, not adequately ensuring the privacy and security of the information contained in the notarized files. In addition, none of the solutions provide a custom template for notarized files and a massive file upload feature to help users with tasks in the notarization process. Finally, the free storage space provided by only one of these solutions is only 10 MB, which is too small to store large files (such as dissertations, project documents, AutoCAD files, etc.).