How SSH Works: Keys, Agents, and Tunnels Explained

SSH is a secure protocol used to connect to and manage remote Linux servers. It provides encrypted access for running commands, transferring files, and forwarding network traffic. SSH relies on a client-server architecture and uses keys for authentication.

What happened

SSH Essentials guide covers the fundamentals and practical details required to work effectively with SSH. It explains how SSH authentication works, how trust is established using keys, and how to configure SSH securely on both the server and client side.

SSH trust is established ahead of time, not during login. Servers trust public keys placed in authorized_keys, and clients prove identity by possessing the matching private key. Private key protection is critical to SSH security.

Why it matters

A secure SSH baseline dramatically reduces exposure. Disabling password logins, blocking direct root access, limiting attempts, and explicitly allowing users should be standard practice. SSH keys authenticate users, while host keys protect clients from connecting to impersonated servers.

How to think about it

To work effectively with SSH, understand the client-server architecture, key-based authentication, and trust establishment. Use SSH keys instead of passwords and protect private keys with permissions and optional passphrases.

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