SSH ED25519

Ever tried to SSH somewhere and got hit with this?

"no mutual signature algorithm"

That’s your sign it’s time to stop using RSA. It’s been deprecated for a while now, and for security reasons ED25519 is the one you want.

Question 1: Can I convert my existing RSA key to ED25519?

Answer: Nope. They’re different algorithms, so there’s no converting. You just generate a fresh ED25519 key instead.

Generate a new SSH key with ED25519

$ ssh-keygen -t ed25519

Once it’s done, you’ll have two new files.

id_ed25519
id_ed25519.pub

Question 2: Can I mix RSA and ED25519?

Answer: Yes! If some old server still only speaks RSA, you can tell SSH to use more than one key. Here’s how.

Create or edit your .ssh/config

Host *
  AddKeysToAgent yes
  UseKeychain yes
  IdentityFile ~/.ssh/id_ed25519
  IdentityFile ~/.ssh/id_rsa

In this example, every host tries id_ed25519 first, then falls back to id_rsa if that doesn’t work.

Keep secured !