An Efficient Hybrid Cryptographic Approach For Secure Cloud Data Storage Using Cipher-diversified Block Dispersal And Blinded Rsa Key Encapsulation

Abstract

Cloud Storage Has Become The Default Medium For Retaining Large Volumes Of Sensitive Records, Yet The Loss Of Physical Custody Over That Data Leaves Owners Dependent On Controls They Cannot Inspect. Single-algorithm Encryption Addresses Only Part Of The Problem: Symmetric Ciphers Are Fast But Expose The Secret Key During Distribution, Whereas Asymmetric Ciphers Protect Key Exchange At A Computational Cost That Is Impractical For Bulk Payloads. This Paper Presents An Efficient Hybrid Cryptographic Approach That Couples Four Primitives—AES-256, Blowfish-448, A One-time Password (OTP) Mechanism And An Enhanced RSA Construction—inside A Three-tier User–proxy–storage Architecture. Plaintext Is Partitioned Into Fixed-length Blocks, And Each Block Is Assigned To Either AES Or Blowfish By A Pseudo-random Cipher Selector Seeded From The Session OTP, So That Cryptanalytic Success Against A Single Cipher Never Yields The Complete File. Session Keys Are Multiplicatively Blinded By An Auxiliary Composite Factor Derived From User Credentials Before RSA Encapsulation, And A Merkle Root Computed Over The Per-block Digests Is Signed With RSA-PSS To Supply Integrity And Non-repudiation. The Resulting Cipher Blocks Are Dispersed Across Independent Storage Zones Together With An Encrypted Manifest. Evaluation On A Healthcare Record Corpus Records A Sustained Throughput Of 93.5 MB/s, A 33.0% Reduction In Encryption Latency And A 34.1% Reduction In Decryption Latency Relative To An AES-OTP-RSA Baseline, A Tamper-detection Accuracy Of 99.47%, And Mean Squared Error Of 0.198.

Keywords