Slink — Secure Terminal-to-Terminal Communication System

Slink is a production-quality, security-first terminal-to-terminal text messaging application written in Python 3.12+. It enables direct peer-to-peer encrypted text communication between two computers with peer authentication, forward secrecy, replay protection, session key rotation, and interactive terminal UX.

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Key Features

• Direct Peer-to-Peer: Communication flows directly between terminals over TCP. No central server or database required.
• End-to-End AEAD Encryption: Authenticated encryption using ChaCha20-Poly1305 (or AES-256-GCM).
• Identity Signatures: Long-term Ed25519 identity keypairs for peer authentication.
• Forward Secrecy: Ephemeral X25519 key agreement for every session.
• Replay Protection: Monotonic 64-bit sequence numbers and sliding-window anti-replay filter.
• Key Rotation: Automatic periodic session key derivation via HKDF-SHA256.
• Trust-On-First-Use (TOFU): Formatted identity fingerprints and peer database with security alerts on identity key changes.
• Interactive Terminal UX: Clean terminal session view with live message streaming and interactive slash commands (/help, /status, /peers, /fingerprint, /clear, /quit).
• Cross-Platform: Windows 10/11, Linux, macOS.

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Installation & Setup

Quick Install (PyPI)

pip install slink-terminal

Once installed, run Slink directly from any terminal:

slink

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Development Installation

# Clone or open repository directory
cd d:/Projects/Terminal

# Create virtual environment
python -m venv .venv

# Activate virtual environment
# Windows PowerShell:
.\.venv\Scripts\Activate.ps1

# Install dependencies and editable package
pip install -r requirements.txt
pip install -e .

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Usage Guide

1. Check Local Identity & Fingerprint

slink identity show
slink identity fingerprint

2. Start Listener (Computer A)

# Listen on default port 9000
slink listen

# Listen on custom port with LAN discovery enabled
slink listen --port 9000 --discover

3. Connect to Listener (Computer B)

# Connect to peer IP address and port
slink connect 192.168.1.10:9000

# Connect using IPv6 address
slink connect "[2001:db8::10]:9000"

4. Interactive Chat Session

Once connected, type text messages directly. Use slash commands inside the terminal:

• /help — Display list of commands
• /status — View current session encryption status and message count
• /fingerprint — Show local identity fingerprint
• /peers — List trusted peer records
• /clear — Clear terminal buffer
• /quit — Gracefully terminate encrypted session

5. Peer Discovery

slink discover

6. Configuration Management

slink config show
slink config set port 9000
slink config set max-message-size 65536

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Building Executable for Windows (slink.exe)

PyInstaller packaging script is provided in scripts/build_windows.ps1.

To build a standalone executable:

.\scripts\build_windows.ps1

The compiled executable will be generated at dist\slink.exe.

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Security Model & Limitations

Security depends on:

• Correct implementation of cryptographic primitives (cryptography library).
• Verification of peer identity fingerprints upon initial connection.
• Endpoint OS security (protection against malware, keyloggers, and physical theft).

Disclaimer: Slink does not protect against compromised endpoints, hardware keyloggers, or OS-level memory extraction by administrative malware.

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Running Tests & Benchmarks

# Run full unit, integration, and security test suite
pytest

# Run performance benchmark
python tests/benchmark.py