A Polynomial Symmetric Key Sharing Scheme with Cheater Detection for Cloud Storage using Ethereum Blockchain

Cloud computing enables on-demand access to a shared pool of configurable resources following a pay-per-use model. Cloud storage offers unlimited data storage, secure data access, and efficient backups. To ensure data confidentiality in the cloud, a symmetric encryption method is used. A key challenge is ensuring the secure sharing of the symmetric key with users. Various approaches have been proposed to address this issue, with the polynomial secret sharing method being one of the most widely utilized techniques. In this approach, the secret key is divided into “n” shares and the user needs at least “t” shares to reconstruct the key. The correctness of the reconstructed key is verified by decrypting the encrypted data; successful decryption confirms the key’s accuracy, while failure indicates otherwise. Validating key shares before reconstruction is essential, as reconstruction involves significant computational effort. Therefore, an efficient approach ensures that shares are validated prior to reconstruction. This paper proposes a polynomial-based symmetric key sharing scheme with cheater detection, designed for a cloud environment using blockchain technology. The key shares are distributed and stored among “n” miners in the blockchain network. To reconstruct the key, at least “t” miners must respond with their respective key shares. Before reconstruction, the key shares are validated using a tag-based approach. The suggested secret sharing scheme is implemented through the deployment of Ethereum smart contracts, and a cost analysis of the functions of the deployed contract is also presented.