Untitled

graph TD
    %% Define Styles
    classDef start_end fill:#FF5555,stroke:#333,stroke-width:2px,color:#fff;
    classDef input_output fill:#5555FF,stroke:#333,stroke-width:2px,color:#fff;
    classDef process fill:#00CC66,stroke:#333,stroke-width:2px,color:#fff;
    classDef loop fill:#FF9900,stroke:#333,stroke-width:2px,color:#fff;

    A([Start]) :::start_end
    A --> B[/Enter 64-bit Plaintext/] :::input_output
    B --> C[/Enter 64-bit Key/] :::input_output
    C --> D[Initial Permutation - IP] :::process
    D --> E[Divide into Left L and Right R Halves] :::process
    E --> F[Generate 16 Round Keys] :::process
    
    subgraph Rounds [16 Feistel Rounds]
    direction TB
    G[Expansion Permutation - E] :::loop
    G --> H[XOR with Round Key] :::loop
    H --> I[S-Box Substitution] :::loop
    I --> J[P-Box Permutation] :::loop
    J --> K[XOR with Left Half] :::loop
    K --> L[Swap Halves] :::loop
    end
    
    F --> Rounds
    Rounds --> M[Combine Halves] :::process
    M --> N[Final Permutation - IP-1] :::process
    N --> O[/Generate Ciphertext/] :::input_output
    O --> P([End]) :::start_end