SSH Explained: How It Works and What to Look For
SSH provides a secure transport for remote login and other network services.
Published by Protocol Explorer · Reviewed
How SSH works
The parties negotiate algorithms and establish keys, authenticate the server, then authenticate the user before opening channels for services.
What to look for in an exchange
Separate transport negotiation, user authentication and the connection protocol. A server host key authenticates the server; it is not the same as a user key.
Follow an example step by step
- Find the version exchange and the key-exchange negotiation.
- Observe server host-key verification and then the user-authentication stage.
- After authentication, follow channel requests for a shell, command or other service.
Common interpretation mistake
A user key and a server host key prove different identities.
Key point to remember
After encryption is enabled, an ordinary network capture cannot read the protected SSH session contents.
Explore the protocol
The SSH overview is free without an account. Its full interactive lesson is included in Protocol Explorer Pro, a one-time $4.99 purchase; an account is required to buy Pro and restore the licence across devices.
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Specification
Read the primary specification for SSH for the authoritative protocol details. The interactive scenario is a simplified teaching model, not a capture of your network.
Continue learning
How to read a packet · TCP · UDP · HTTPS