# Security Layer

The Security Layer implements secure group communications using the Message Layer Security (MLS) protocol. This layer ensures end-to-end encryption, authentication, and access control across agent groups within the AGP ecosystem.

## Overview

The security layer leverages MLS to provide:

- Quantum-safe end-to-end encryption (QSE2EE) for group communications
- Dynamic group membership management
- Forward secrecy and post-compromise security
- Scalable key management for large agent groups

## Key Components

### 1. Group State Management

- Maintains cryptographic group state
- Handles member additions and removals
- Manages group epoch changes
- Processes key updates

### 2. Key Schedule

- Derives encryption keys from group secrets
- Implements MLS key schedule
- Manages key rotations
- Ensures forward secrecy

### 3. Message Protection

- Encrypts group messages
- Provides integrity protection
- Implements sender authentication
- Handles message sequencing

### 4. Authentication

- Validates group members
- Verifies message signatures
- Manages identity credentials
- Implements access control

## Security Properties

- **Forward Secrecy**: Ensures past communications remain secure if keys are compromised
- **Post-Compromise Security**: Provides security guarantees after member compromise
- **Group Authentication**: Verifies message origin within the group
- **Message Confidentiality**: Protects message content from unauthorized access

## Integration

The security layer integrates with:

- Transport layer for secure message delivery
- Session layer for maintaining secure contexts
- Identity services for credential management

```mermaid
graph TB
    %% Services
    AS[Authentication Service]
    DS[Delivery Service]

    %% Service Connection
    AS <--> DS

    %% Clients and Members
    Client1[Client 1]:::client
    Client2[Client 2]:::client
    Client3[Client 3]:::client

    %% Group Definition
    subgraph MLSGroup[MLS Group]
        Member1[Member 1]:::member
        Member2[Member 2]:::member
    end

    %% Client Authentication
    Client1 --> AS
    Client2 --> AS
    Client3 --> AS

    %% Client-DS Connections
    Client1 -.-> DS
    Client2 --> DS
    Client3 --> DS

    %% Member Associations
    Client2 === Member1
    Client3 === Member2

    %% Styles
    classDef service fill:#ffffff,stroke:#000000,stroke-width:2px
    classDef client fill:#f0f0f0,stroke:#000000,stroke-width:2px
    classDef member fill:#e0e0e0,stroke:#000000,stroke-width:2px

    class AS,DS service
    class Client1,Client2,Client3 client
    class Member1,Member2 member
```