ssh

The Secure Shell Protocol is a cryptographic network protocol for operating network services securely over an unsecured network. Typical applications include remote command-line, login, and remote command execution, but any network service can be secured with SSH.

SSH supports a handful of types of cryptographic keys. The most used are RSA and the more modern ed25519.

RSA is the de-facto standard and is supported everywhere (just choose a big enough key like 4096 bits to be secure). Ed25519 is designed to be faster and smaller withouth sacrificing security, so is best suited for embedded devices or machines with low resources. It's supported on tilde (and really on any modern system) but you may find older systems which do not support it.

Keep in mind that these instructions leave your private keys unencrypted in your local hard disk. So keep them private; never share them. A good solution is to provide a password for them at creation time, but this implies entering a password any time you used them (impractical) or use something like ssh-agent (a bit more complex)

Linux

Generating your keypair

Make sure you have a ~/.ssh directory (the -m 700 ensures it has the correct file permissions)

mkdir -m 700 ~/.ssh

Create your keys

ssh-keygen -t ed25519 -a 100

If you press enter to accept the defaults, your public and private key will be located at ~/.ssh/id_ed25519.pub and ~/.ssh/id_ed25519 respectively

cat ~/.ssh/id_ed25519.pub

Copy the output of the last command and paste it in the sshkey field on the signup form or email it to the relevant sign-up address for the tilde you are joining.

Using your keypair

ssh to your tilde

ssh username@your.tilde

Mac

Generating your keypair

• Open terminal (it’s in /Applications/Utilities)
• Make sure you have a ~/.ssh directory (the -m 700 ensures it has the correct file permissions)

mkdir -m 700 ~/.ssh

Create your keys

ssh-keygen -t ed25519 -a 100

If you press enter to accept the defaults, your public and private key will be located at ~/.ssh/id_ed25519.pub and ~/.ssh/id_ed25519 respectively

cat ~/.ssh/id_ed25519.pub

Copy the output of the last command and paste it in the sshkey field on the signup form or email it to the relevant sign-up address for the tilde you are joining.

Using your keypair

ssh to your tilde:

ssh username@your.tilde

Windows

Choose a SSH method

There are several options for using SSH on Windows. Depending on which you choose your process will look slightly different.

PuTTY

• Install PuTTY
• Use puttygen to generate a key
• Save private and public keys
• Copy the text of the public key and paste it in the sshkey field on the signup form or email it to the relevant sign-up address for the tilde you are joining.
• When your account has been approved, start pageant (this will put an icon of a computer wearing a hat into the System tray)
• Right click the icon and choose View Keys
• Click the Add Keys button
• Select the private key you created earlier and open it
• Start putty and connect to your username at the server address of the tilde you joined

ssh username@your.tilde