WARNING this command may overwrite an existing key with the same name ( ~/.ssh/id_ed25519-atlas in this example), thus please ensure this key does not yet exist!

Key creation

Open a terminal and create a new key-pair:

mkdir -p ~/.ssh
chmod 700 ~/.ssh
ssh-keygen -t ed25519 -a 512 -f ~/.ssh/id_ed25519-atlas

The last command will ask you for a passphrase, please choose a long and good one. The usual suggestion for a password is to use at least 16 characters with mixed types with a few digits and special characters. Please be sure, to use only special characters which are available on most keyboards you may use in the future. A passphrase is usually longer then a password and easier to type, but should still have a few special characters and digits. Over time, you may memorize this one assuming you will type it regularly, at least until then it is perfectly fine to store it in a “password safe” provided you protect this one with a very good password/-phrase.

With a few other configuration steps, you will not need to type it in often, thus please use a sufficiently long and secure passphrase!

The option proposed by us are (more information can be found via man ssh-keygen):

-t ed25519
This selects the type of key (which algorithm is used), at the moment ed25519 looks like a secure algorithm with the benefit of small sized public keys.
-a 512
Whenever a private key is entered, the relevant algorithm is not applied once but 512 times. This is useful against brute force attacks as it heavily slows down cracking attempts. We think 512 is a good compromise for local usage, as it will cause a noticeable delay but should not annoy you. If you have a very powerful local machine, feel free to increase this number.
~/.ssh/id_ed25519-atlas
This instructs ssh-keygen to save the private key as ~/.ssh/id_ed25519-atlas and the public key as ~/.ssh/id_ed25519-atlas.pub

Once done, you can safely send us the file ~/.ssh/id_ed25519-atlas.pub (the so-called public key) by email. But remember, the private key should never leave your local machine!