1. Introduction
  1.1 Background
  1.2 Objectives
2. Literature Review
  2.1 Overview of Secure Messaging Protocols
  2.2 Analysis of Existing Messaging Applications
3. System Architecture and Design
  3.1 Security Requirements and Threat Model
  3.2 End-to-End Encryption Scheme
  3.3 Key Exchange and Authentication Mechanisms
  3.4 User Interface Design Considerations
4. Implementation
  4.1 Selection of Development Tools and Technologies
  4.2 Coding and Testing of Security Features
5. Integration and Compatibility
  5.1 Interoperability with Existing Messaging Platforms
  5.2 User Experience Testing and Feedback