# Introduction

License Manager is an independent software licensing management system that provides license code generation, distribution, validation, and management services for software systems. The system supports both enterprise-level management backend and user-end self-service, supporting both online and offline licensing modes, with hardware-based binding mechanisms ensuring security.

## System Overview

License Manager is an enterprise-grade software licensing management solution that provides dual-end service modes:

- **Enterprise End**: Helps software vendors achieve a complete lifecycle management cycle from license generation, distribution, validation to full lifecycle management
- **User End**: Provides end users with convenient self-service for purchasing, activating, and managing licenses, supporting mobile phone registration, online payment, device binding and other functions

The system adopts a frontend-backend separation architecture, providing an intuitive management interface and rich API interfaces, supporting multiple deployment modes to meet licensing management needs in different scenarios.

## Core Features

### 🔐 Flexible Licensing Modes

- **Online Licensing (Cloud)**: Local verification + heartbeat reporting, with remote control and management
- **Offline Licensing (Standalone)**: Hardware fingerprint binding, verification without network connection
- **Hybrid Mode**: Local verification + heartbeat reporting, allow short-term offline operation when disconnected

### 🛡️ Security Mechanisms

- **Hardware Binding**: Prevent license copying through device fingerprints (MAC, CPU, HostID, etc.)
- **Digital Signatures**: RSA-PSS-SHA256 signatures ensure license data integrity
- **State Management**: Support multiple states including normal, locked, expired, with remote control capabilities
- **Key Encryption**: Encrypted storage and transmission of license data

### 📊 Full Lifecycle Management

- **Customer Management**: Unified maintenance of customer profiles, contacts, and license relationships
- **License Generation**: Batch generation, custom validity periods, feature restriction configuration
- **Status Monitoring**: Real-time license status viewing, usage statistics
- **Operation Auditing**: Complete operation log records for traceability and auditing

### 👤 User Self-Service

- **Self-Service Purchase**: Users register and log in via mobile phone, select packages and device quantities, pay via Alipay
- **One-Click Activation**: After obtaining license code, open the software product and enter the license code, system automatically binds device and activates
- **Order Management**: Support viewing order history, applying for invoices and other services
- **Device Management**: Support viewing bound devices, unbinding unnecessary devices
- **Auto Renewal**: Support heartbeat monitoring and automatic renewal reminders

### 🚀 Easy Integration

- **RESTful API**: Standardized API interfaces, easy to integrate with existing systems
- **Client SDK**: Client verification libraries in multiple languages
- **Deployment Package Generation**: Automatically generate deployment packages with configuration, simplifying delivery processes

## System Architecture

The system adopts a modern **frontend-backend separation architecture** design, with the backend built on the high-performance **Go (Golang)** language. This architecture design ensures system stability under high-concurrency scenarios while greatly simplifying enterprise deployment and operational costs.

### Core Components

```mermaid
graph TD
    UI[💻 Frontend Admin Interface<br/>Vue.js 3 + Modern UI]
    API[⚙️ Backend Core Engine<br/>Go + Gin + GORM]
    DB[(🗄️ MySQL Database<br/>License Data Storage)]

    UI -->|HTTPS / REST API| API
    API -->|TCP / SQL| DB
    
    %% Simple styling
    classDef default fill:#fff,stroke:#333,stroke-width:2px;
```

### Architecture Advantages

* **Ultimate Performance**: Thanks to Go's coroutine (Goroutine) features, a single node can support tens of thousands of concurrent verification requests with extremely low resource consumption.
* **Simple Deployment**: The backend compiles into a single binary file (Single Binary) with zero runtime dependencies, perfectly supporting Docker containerized deployment.
* **Secure and Reliable**: API interface layer adopts strict authentication mechanisms, core business logic is closed-loop on the server side, and the database supports transactional consistency guarantees.
* **Easy to Scale**: Modular code structure design supports smooth upgrade from single-machine mode to cluster high-availability mode.

### Workflow

```mermaid
sequenceDiagram
    autonumber
    participant Admin as 👤 Administrator
    participant System as ⚙️ Core Engine
    participant Client as 🖥️ Client Software

    Note over Admin, System: Phase 1: Generation & Distribution
    Admin->>System: 1. Create License Policy (Web UI)
    System-->>Admin: Generate License File/Key
    Admin->>Client: 2. Distribute License Package (Email/Download)

    Note over Client, System: Phase 2: Verification & Operation
    Client->>Client: 3. Local Verification (Decrypt & Verify Signature)
    
    opt Online Mode
        Client->>System: 4. Report Heartbeat (with License Info)
        System->>System: Check Heartbeat Content
        alt License Update Required
            System-->>Client: Return true (Update Required)
            Client->>System: 5. Auto-download New License
            System-->>Client: Return New License File
            Client->>Client: Update Local License
        else No Update Needed
            System-->>Client: Return false (Normal)
        end
    end
```

1.  **License Issuance**: Administrators configure policies through the frontend interface, and the backend core engine generates tamper-proof license files/keys using encryption algorithms.
2.  **License Distribution**: Supports online automatic distribution or export of offline deployment packages, delivered to end users through secure channels.
3.  **Client-Side Verification**: Client applications integrate SDKs and perform **local verification** (using public key to decrypt and verify signatures) at startup or runtime. Whether in online or offline mode, verification is completed locally without requiring real-time network connection.
4.  **Heartbeat Reporting & License Update**: In online mode, clients periodically report heartbeats (containing license information) to the server. The server checks the heartbeat content to determine if a license update is needed. If an update is required, it returns `true` to the client, and the client automatically downloads the new license and updates the local license file.
5.  **Audit and Monitoring**: The system automatically records verification logs and heartbeat data, providing real-time feedback on license usage status and anomaly alerts.

## Use Cases

- **SaaS Software**: Need to control access permissions by time, features, user count, etc.
- **Enterprise Software**: Require hardware binding to prevent illegal license copying
- **Embedded Systems**: Require offline verification without network dependency
- **API Services**: Need to control usage limits such as call counts, concurrency, etc.
- **Software Trials**: Provide trial period licenses with automatic feature restrictions upon expiration
- **Individual User Software**: Support user self-service purchase, online payment, device binding activation
- **Multi-Device Management**: Support single user using on multiple devices, support device unbinding and reallocation


## Next Steps

- If you are a **new user**, we recommend starting with [Getting Started](./getting-started.md) to learn how to deploy the system
- If you want to understand **why you need a licensing system**, check out [Business Value](./business_value.md)
- If you are a **developer** needing to integrate license validation, please refer to [License Structure](./license-token-structure.md) and [API Reference](./api.md)
- If you want to **contribute** or understand our development philosophy, see [Community Strategy](./community_strategy.md)