Change SSH Key Passphrase

To change SSH key passphrase, run

ssh-keygen -p -f ~/.ssh/id_rsa

Example

root@ok:~/.ssh# ssh-keygen -p -f ~/.ssh/id_rsa
Enter new passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved with the new passphrase.
root@ok:~/.ssh# 

See ssh-keygen