How to Setup SSH Key Authentication Instead of Username/Password

linuxssh

How do you setup ssh to authenticate a user using keys instead of a username / password?

Best Answer

For each user: they should generate (on their local machine) their keypair using ssh-keygen -t rsa (the rsa can be replaced with dsa or rsa1 too, though those options are not recommended). Then they need to put the contents of their public key (id_rsa.pub) into ~/.ssh/authorized_keys on the server being logged into.

Related Solutions

SSH – How to Change Private Key Passphrase

To change the passphrase on your default key:

$ ssh-keygen -p

If you need to specify a key, pass the -f option:

$ ssh-keygen -p -f ~/.ssh/id_dsa

then provide your old and new passphrase (twice) at the prompts. (Use ~/.ssh/id_rsa if you have an RSA key.)

More details from man ssh-keygen:

[...]
SYNOPSIS
    ssh-keygen [-q] [-b bits] -t type [-N new_passphrase] [-C comment]
               [-f output_keyfile]
    ssh-keygen -p [-P old_passphrase] [-N new_passphrase] [-f keyfile]
[...]
     -f filename
             Specifies the filename of the key file.
[...]
     -N new_passphrase
             Provides the new passphrase.

     -P passphrase
             Provides the (old) passphrase.

     -p      Requests changing the passphrase of a private key file instead of
             creating a new private key.  The program will prompt for the file
             containing the private key, for the old passphrase, and twice for
             the new passphrase.
[...]

Git for Windows – How to Tell Git Where to Find Private RSA Key

For Git Bash

If you are running msysgit (I am assuming you are) and are looking to run Git Bash (I recommend it over TortoiseGit, but I lean to the CLI more than GUI now), you need to figure out what your home directory is for Git Bash by starting it then type pwd (On Windows 7, it will be something like C:\Users\phsr I think). While you're in Git Bash, you should mkdir .ssh.

After you have the home directory, and a .ssh folder under that, you want to open PuTTYgen and open the key (.ppk file) you have previously created. Once your key is open, you want to select Conversions -> Export OpenSSH key and save it to HOME\.ssh\id_rsa. After you have the key at that location, Git Bash will recognize the key and use it.

Note: Comments indicate that this doesn't work in all cases. You may need to copy the OpenSSH key to Program Files\Git\.ssh\id_rsa (or Program Files (x86)\Git\.ssh\id_rsa).

For TortoiseGit

When using TortoiseGit, you need to set the SSH key via pacey's directions. You need to do that for every repository you are using TortoiseGit with.