This paper presents the Blockchain-Based Decentralised File Sharing System (BBDFS),also called DecentraShare a complete, production-ready system that solves thethree fundamental weaknesses of cloud-based le sharing: lack of privacy, absence oftamper evidence, and susceptibility to censorship. The system integrates three tech-nologies: the InterPlanetary File System (IPFS) for peer-to-peer distributed storage,Ethereum-compatible smart contracts deployed on the Polygon Proof-of-Stake net-work for programmable access control, and AES-256-GCM symmetric encryptionperformed entirely inside the user's browser via the Web Crypto API.When a le is uploaded, it is encrypted locally before leaving the user's device the backend server never receives plaintext content. A content identier (CID)returned by IPFS is anchored on the blockchain alongside a SHA-256 integrity hash.Three Solidity 0.8.19 smart contracts FileRegistry.sol, AccessControl.sol,and IntegrityLedger.sol manage ownership, per-wallet permission grants andrevocations, and a chained integrity audit log respectively. A stateless Node.js 20/ Express 4.18 backend exposes 19 REST API endpoints, while real-time Server-Sent Events (SSE) deliver access notications to recipients within a median of 18milliseconds.Performance evaluation over 1,500 independent le-transfer trials demonstrates amedian upload latency of 2.58 seconds for 1MB payloads, on-chain conrmationwithin 2.1 seconds on Polygon, and 99.97% data retrievability under normal operat-ing conditions. Gas optimisation reduced smart contract deployment cost by 46.7%over naive reference implementations. Comparative analysis against Storj, Filecoin,Swarm, and AWS S3 conrms that BBDFS is the only evaluated system simultane-ously providing end-to-end encryption, on-chain access control, and tamper-evidentauditing.
Patil et al. (Tue,) studied this question.