Bspace: a group workspace over the Ethereum blockchain with off-blockchain storage
Jae-Hwan Jin, Hyun-Min Eom, Myung-Joon Lee · International Journal of Advanced Computer Research · 2019
IntroductionEthereum [1], a second-generation blockchain [2] technology, supports the development of decentralized applications [3] based on blockchain beyond processing financial transactions.Ethereum uses smart contracts deployed in the blockchain network to perform functions requested by decentralized applications [4].So, the Ethereum applications can store various information in the blockchain network or reliably use the information, while transactions for each request are recorded in the blockchain network.However, Ethereum cannot contain large amounts of data in a single transaction, thus causing problems in storing large files.Generally, Ethereum has a size limit of about 780kb for one transaction, so it is not suitable for storing high-resolution images, music, video files, etc. in the Ethereum blockchain network.Recently, to solve this problem, various developers and applications introduced methods of storing files using offblockchain storage [5]. *Author for correspondenceUsually, in these off-blockchain storage methods, a file is stored in the associated external storage and the hash key of the file, which is the key to access the file, is stored in the blockchain.But these offblockchain storage methods also cause an essential problem that if a hash key of a file was lost, anyone can access the file stored in the external storage using the hash key without a separate authentication procedure.To solve this problem, some developers store encrypted data in external storage.But the encryption of larger size files requires much more computation and storage, and there is still a risk of file loss.In particular, group workspaces, where frequent file sharing among multiple users occurs, are typical examples of large file sharing problems.The blockchain-based group workspace [6] has the advantage of being able to reliably perform group operations among users based on transaction history.But the off-block chain storage does not support access control techniques in association with the access rights of the members of the group workspaces.So, to utilize the off-blockchain storage more securely, it is desirable to prevent the external Research