Mobile Cloud Storage (MCS) System

A secure and privacy-preserving cloud storage system based on the paper:
"Enabling Efficient, Secure and Privacy-Preserving Mobile Cloud Storage" (IEEE TDSC 2022).

Features

• Data Confidentiality: Encrypted storage using Damgård-Jurik cryptosystem.
• Access Pattern Privacy: Oblivious retrieval/update via Stash and BinaryTree.
• Temporal Locality: Caching for frequently accessed items.
• Verification Chunks: Integrity checks against malicious clouds.

Components

Module	Description
core.py	Core (Stash, PositionMap, BinaryTree)
cloud.py	Mobile Cloud Client or Storage
damgard_jurik	Homomorphic encryption (External Library)
main.py	Example usage

Example Workflow: get(key=5)

Step-by-Step Process

sequenceDiagram
    participant Client
    participant PositionMap
    participant Stash
    participant Cloud
    participant BinaryTree

    Note over Client: Request get(key=5)
    Client->>Stash: Check temporal locality (cached?)
    alt Item in Stash (Cached)
        Stash-->>Client: Return value (fast path)
    else Not in Stash
        Client->>PositionMap: Lookup location of key=5
        PositionMap-->>Client: (level=2, index=1)
        Client->>Cloud: Request bucket (2,1)
        Cloud->>BinaryTree: Retrieve encrypted bucket
        BinaryTree-->>Cloud: Return bucket
        Cloud-->>Client: Return encrypted data
        Client->>Stash: Push (key=5, value) for future access
        Client->>Stash: Pop oldest item for eviction
        Client->>Cloud: Write evicted item to random dummy location
        PositionMap->>PositionMap: Update key mappings
    end
    Client-->>Client: Decrypt and return value

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How to Run

  python demo.py