Mastering SSH Key Generation

Introduction

SSH keys provide a robust, secure method of authentication that significantly enhances your digital security. This guide walks you through generating, configuring, and deploying SSH keys across multiple platforms.

Why SSH Keys Matter

Traditional password-based authentication is vulnerable to:

• Brute-force attacks
• Credential interception
• Repeated login attempts

SSH keys offer:

• Stronger encryption
• Protection against password-guessing attacks
• More secure, key-based authentication
• Simplified access management

Generating SSH Keys: Cross-Platform Guide

Prerequisites

• Modern terminal/command prompt
• OpenSSH (pre-installed on most systems)
• Internet connection

Key Generation Algorithms

We recommend using these key types:

1. Ed25519: Modern, high-performance, compact
2. RSA: Widely supported (4096-bit recommended)

Windows (Multiple Methods)

Method 1: Windows Subsystem for Linux (Recommended)

# Install WSL (Windows Subsystem for Linux)
wsl --install

# Open WSL terminal
ssh-keygen -t ed25519 -C "[email protected]"

Method 2: Git Bash

# Open Git Bash
ssh-keygen -t ed25519 -C "[email protected]"

Method 3: PowerShell (Native OpenSSH)

# Generate ED25519 key
ssh-keygen -t ed25519 -C "[email protected]"

macOS

# Open Terminal
ssh-keygen -t ed25519 -C "[email protected]"

Linux

# Open Terminal
ssh-keygen -t ed25519 -C "[email protected]"

Key Generation Workflow

1. Run the ssh-keygen command
2. When prompted for file location, press Enter (default is fine)
3. Enter a strong passphrase

• Use a password manager
• Minimum 16 characters
• Mix of uppercase, lowercase, numbers, symbols

Key File Protection

• Private key (id_ed25519): Never share
• Public key (id_ed25519.pub): Can be distributed

Deploying SSH Keys

Linux Server Deployment

# Copy public key to server
ssh-copy-id -i ~/.ssh/id_ed25519.pub username@server_ip

# Manual method
# 1. Copy key contents
cat ~/.ssh/id_ed25519.pub

# 2. On server, add to authorized_keys
mkdir -p ~/.ssh
chmod 700 ~/.ssh
echo "PASTE_PUBLIC_KEY_HERE" >> ~/.ssh/authorized_keys
chmod 600 ~/.ssh/authorized_keys

GitHub Deployment

Method 1: Web Interface

1. Copy public key

cat ~/.ssh/id_ed25519.pub

2. GitHub → Settings → SSH Keys → New SSH Key
3. Paste key, add descriptive title

Method 2: GitHub CLI

# Install GitHub CLI
# Debian/Ubuntu
sudo apt install gh

# macOS
brew install gh

# Add SSH key
gh auth login
ssh-add -K ~/.ssh/id_ed25519
gh ssh-key add ~/.ssh/id_ed25519.pub

Advanced Security Configurations

SSH Config Hardening (~/.ssh/config)

Host *
    AddKeysToAgent yes
    UseKeychain yes
    IdentityFile ~/.ssh/id_ed25519
    ServerAliveInterval 60
    ServerAliveCountMax 3

Key Management Tips

• Rotate keys annually
• Use different keys for different services
• Store private keys securely
• Consider hardware security keys

Troubleshooting Common Issues

Key Permissions

# Fix key permissions
chmod 700 ~/.ssh
chmod 600 ~/.ssh/id_ed25519
chmod 644 ~/.ssh/id_ed25519.pub

Security Warning

• Never share your private key
• Use strong, unique passphrases
• Enable two-factor authentication where possible