implementing-end-to-end-encryption-for-messaging

# Implementing End-to-End Encryption for Messaging ## Overview End-to-end encryption (E2EE) ensures that only the communicating parties can read messages, with no intermediary (including the server) able to decrypt them. This skill implements a simplified version of the Signal Protocol's Double Ratchet algorithm, using X25519 for key exchange, HKDF for key derivation, and AES-256-GCM for message encryption. ## When to Use - When deploying or configuring implementing end to end encryption for messaging capabilities in your environment - When establishing security controls aligned to compliance requirements - When building or improving security architecture for this domain - When conducting security assessments that require this implementation ## Prerequisites - Familiarity with cryptography concepts and tools - Access to a test or lab environment for safe execution - Python 3.8+ with required dependencies installed - Appropriate authorization for any testing activities ## Objectives - Implement X25519 Diffie-Hellman key exchange for session establishment - Build the Double Ratchet key management algorithm - Encrypt and decrypt messages with per-message keys - Implement forward secrecy (compromise of current key does not reveal past messages) - Handle out-of-order message delivery - Implement key agreement using X3DH (Extended Triple Diffie-Hellman) ## Key Concepts ### Signal Protocol Components | Component | Purpose | Algorithm | |-----------|---------|-----------|...