Decentralized Cloud Storage Architecture Using Block Chain for Data Integrity

Abstract

Cloud computing offers scalable storage but raises concerns over data integrity and trust due to centralized control. This project presents a decentralized cloud storage system using blockchain to ensure secure, transparent, and tamper-proofdata handling. By integrating cryptographic hashing, smart contracts, and audit logging, the system allows users to verify data integrity without third-party auditors. Implemented with ASP.NET and C#, the prototype demonstrates secure uploads, controlled access, and verifiable audit trails, forming a foundation for future blockchain-enabled cloud systems.

Introduction

Cloud computing has revolutionized data handling by offering scalable, cost-effective, and remote access to storage and processing. However, the centralized trust model—where users must rely on Cloud Service Providers (CSPs) for confidentiality, integrity, and availability—has serious flaws, especially in sensitive domains like healthcare, banking, and government.

• Major concerns:

  • Data breaches

  • Insider threats

  • Lack of transparency

  • No verifiable guarantees for users

• Traditional solutions (encryption, tokens, access control) provide some security but lack auditability and tamper-evidence.

2. Blockchain as a Solution

Blockchain introduces a decentralized, transparent, and immutable ledger, eliminating the need for blind trust.

• Benefits of Blockchain in Cloud Storage:

  • Traceable, timestamped, and cryptographically linked records

  • Built-in auditability and tamper resistance

  • Aligns with data sovereignty and regulatory compliance demands

  • Enables innovations like decentralized identity, federated clouds, and AI-powered anomaly detection

3. Literature Review

Key developments leading to this approach include:

• Public auditability: Q. Wang et al. introduced Third-Party Auditors (TPAs), which reduced communication overhead but reintroduced central dependency.

• Bitcoin & Blockchain (Satoshi Nakamoto): Provided the foundation for decentralization and immutability.

• Multi-cloud auditing: X. Chen et al. developed frameworks using blockchain for dynamic user revocation and traceability.

• Provable Data Possession (PDP): G. Ateniese et al. enabled clients to verify stored data without downloading it.

• Privacy-preserving access control: M. Li and H. Tian developed fine-grained, patient-centric models for sensitive domains using attribute-based encryption.

4. Methodology

A modular, decentralized architecture is proposed, consisting of five key components to ensure security, verifiability, and autonomy:

A. User Authentication Module

• Secure login using ASP.NET Identity

• Validates user credentials via hash functions

• Forms the base for access control and audit logs

B. File Management Module

• File operations (upload, download, share)

• Files are encrypted client-side using AES-256

• Integrity ensured with SHA-256 hashing

C. Blockchain Ledger Module

• All actions recorded as immutable blocks

• Provides a tamper-proof, decentralized log of file events

• No need for centralized audit authority

D. Smart Contract Module

• Access control via smart contracts (coded in C#)

• Automatically validate permissions before allowing access

• Events logged to the blockchain for transparency

E. Audit Logging Module

• Logs all user activities (logins, uploads, downloads, etc.)

• Integrates with blockchain for traceability

• Frontend shows logs and alerts for suspicious activity

5. Evaluation & Results

A. Data Integrity Verification

• Files hashed with SHA-256 during upload and rechecked on download

• 100% hash match accuracy in all test scenarios → No tampering detected

B. Access Control Effectiveness

• Tested with different user roles (owner, authorized, unauthorized)

• Smart contracts correctly enforced access permissions in all cases

Conclusion

The proposed decentralized cloud storage architecture using blockchain effectively addresses critical challenges associated with centralized cloud systems, particularly those concerning data integrity, transparency, and access control. By integrating cryptographic hashing, AES-based encryption, and a simulated blockchain ledger, the system ensures that every file operation—whether upload, download, or sharing—is verifiable, immutable, and tamper-evident. The inclusion of role-based smart contract logic further strengthens data confidentiality by enforcing strict access policies without relying on third-party trust. Through modular design, the framework enables secure user authentication, encrypted file management, decentralized audit logging, and automated permission handling. The evaluation metrics including hash verification accuracy, smart contract enforcement, audit traceability, and performance efficiency collectively demonstrate that the system meets its design goals. The methodology not only reinforces user autonomy by eliminating reliance on centralized entities but also aligns with modern compliance demands for traceability and accountability.

References

[1] Y.Zhang,J.Liu,D.Guo,andD.Liu,“Secure and Efficient Public Integrity Auditing Scheme for Cloud Storage,” IEEE Access, vol. 8, pp. 112536–112547, 2020. [2] X.Chen,J.Li,X.Huang,J.Ma,andW.Lou,“New Public Integrity Auditing with Efficient User Revocation for Multi-Cloud Storage,” IEEE TransactionsonComputers,vol.65,no.8,pp.2363–2375,2016. [3] A.Dorri,M.Steger,S.S. Kanhere,andR.Jurdak, “Blockchain: A Distributed Solution to Automotive Security and Privacy,” IEEE Communications Magazine, vol. 55, no. 12, pp. 119–125, 2017. [4] Z. Zheng, S. Xie, H. Dai, X. Chen, and H. Wang, “An Overview of Blockchain Technology: Architecture, Consensus, and Future Trends,”in IEEE International Congress on Big Data, 2017. [5] R. Deng,R. Lu, C. Lai,T.H. Luan, and H. Liang, “Optimal Workload Allocation in Fog-Cloud Computing Toward Balanced Delay and Power Consumption,” IEEE Internet of Things Journal, vol. 3, no. 6, 2016. [6] L. Luu, D. Chu, H. Olickel, P. Saxena, and A. Hobor, “Making Smart Contracts Smarter,” in Proceedings of the ACM SIGSAC Conference on Computer and Communications Security (CCS), 2016. [7] J.Li,Y.Shi,andY.Zhang, “Searchable Ciphertext- Policy Attribute-Based Encryption with Revocation in Cloud Storage,” International Journal of Applied Cryptography, 2016. [8] J. Yu, K. Ren, C. Wang, and V. Varadharajan, “Enabling Cloud Storage Auditing with Verifiable Outsourcing of Key Updates,” IEEE Transactions on Information Forensics and Security ,vol.11,no.6,pp. 1362–1375, 2016.

Copyright

Copyright © 2025 Miss. Tafeem, Mrs. Jennifer Mary S. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.