SSH (Secure Shell)

SSH is a protocol for creating encrypted network connections on insecure networks, such as the Internet. It’s a secure replacement for Telnet. When you log in to an SSH server, all credentials are transmitted securely, including your password and private SSH key.

SSH works over TCP, which means that if the network connection is interrupted, the session may be lost. (That’s where Mosh comes in handy.)

Below is a comprehensive list of what SSH capabilities are currently supported in the app and what will be added soon.

Key Exchange Methods

Host Key Types

Ciphers

MAC Hashes

Authentication Methods

Key Formats

*(As of now) except those keys encrypted with the GCM algorithms

Key Types

Proxy

Mosh (Mobile Shell)

​Mosh is a companion protocol to SSH that maintains sessions when TCP is interrupted. It employs a parallel UDP session which can keep the session alive if TCP breaks. That also enables Mosh to maintain its own terminal buffer that intelligently echoes your input, even if the server is slow or the network lags. No more waiting patiently on slow connections to see what you typed.

The enhancements provided by Mosh are really important to reliable mobile connectivity. If your device changes networks or loses connection, Mosh can keep your session alive until your connection is re-established.

The Mosh service is distinct from SSH, and must be installed and configured separately on your host system. Once the service is up and running, you’re free to roam with Termius — just enable Mosh in your host entry, and connect.

Termius uses its own library for Mosh compatibility.

Telnet

Telnet is a protocol for establishing unsecured remote terminal connections. It does not encrypt anything, even your password, so it should never be used for transacting sensitive information.

However, Telnet is still useful in some scenarios, such as interfacing at a diagnostic level with network hardware, or watching ASCII art at towel.blinkenlights.nl. Under the hood, Termius relies on this implementation of the protocol.