DAGShare: A Secure and Efficient Distributed Personal File Sharing System

Many approaches have been proposed to share data in a decentralized manner using blockchain, which solves many security and data management issues but has some limitations, such as transaction fees, mining time, power consumption, etc. The alternative to a traditional blockchain is using IOTA, a directed acyclic graph (DAG) based system, but this also has the limitation of on-chain storage. To address these challenges we propose DAGShare, a DAG-based system with off-chain storage on an interplanetary file system (IPFS), a content-based addressable system. The DAGShare combines the IOTA network and IPFS to provide a secure and scalable personal file-sharing system in which members can create new groups and join other groups. The system inherits blockchain features and resolves its limitations. The system also provides an access control mechanism to grant system access rights by using IPFS-cluster-service that is not present in the IPFS server and IOTA. We provide a security evaluation of our system using the AVISPA tool and show that it is not only secure but also scalable as compared with IOTA using file sharing and retrieval experiments.