Add ssh pass phrase after setup?

Question

Can an ssh pass phrase added after ssh is already setup? I'm using Debian 8 stable Jessie 8.7. And how can you save it in Debian like in a keyring so you do not have to enter it everytime? Thanks to all for the answers.

Answer 1

SSH uses your normal user password, so it can be changed with the passwd command on the machine you're connecting to.

By default, Debian has public/private key authentication enabled, so you can use RSA keys instead of a passphrase, if you put your public key on the system you're connecting to. First, you need to create a key on your local machine:

ssh-keygen

Then, put it on the remote server. Type this command on your local machine:

cat ~/.ssh/id_rsa.pub | ssh user@remotehost "mkdir -p ~/.ssh && cat >>  ~/.ssh/authorized_keys"

Then you will no longer need a password to log in.

EDIT: @EEAA brings up a good point: ed25519 is a much better cryptographic system nowadays than RSA, and it might be a good idea to start switching. You can create an ed25519 public/private key pair and copy it to your remote system like so:

ssh-keygen -t ed25519
cat ~/.ssh/id_ed25519.pub | ssh user@remotehost "mkdir -p ~/.ssh && cat >>  ~/.ssh/authorized_keys"

There's an interesting read regarding ed25519 vs RSA over in the StackExchange IS community

Answer 2

If your question is how to add a pass phrase to an existing ssh key that is not secured with a password?

You can change the pass phrase with ssh-keygen:

ssh-keygen -p -f ~/.ssh/private-key-file