Passwords in Emacs tramp mode editing

I'm using emacs tramp mode to remotely edit files over ssh. The problem is that every time I save the file I'm editing I have to enter my user password. I find that very annoying. How can I write my password only once / editing session?

From stackoverflow Jonas

• Ah, from the tramp docs on password caching you can set:

  (setq password-cache-expiry nil)
  

  which requires the package password-cache.el.

  Also, in the tramp sources, it mentions reading the ssh-agent(1) man page, which shows how to set it up so that you don't have to re-enter passwords (inside, or outside of Emacs):

  There are two main ways to get an agent set up: The first is that the agent starts a new subcommand into which some environment variables are exported, eg ssh-agent xterm &. The second is that the agent prints the needed shell commands (either sh(1) or csh(1) syntax can be generated) which can be evalled in the calling shell, eg eval ssh-agent -s for Bourne-type shells such as sh(1) or ksh(1) and eval ssh-agent -c for csh(1) and derivatives.

  Török Gábor : The package name is `package-cache`.

  Trey Jackson : (belated) Credit to Török for the package name.
  From Trey Jackson

• (setq password-cache-expiry nil)
  

  Jonas : Should this go into my .emacs file?

  dfa : yes, right after (require 'tramp)
  From dfa

• In addition to Trey Jackson's solution, there are a few more ways you can choose:

  • If you're on a *nix system, you can mount the remote directory with FUSE/SSHFS, and therefore you can edit files as they were on the local file system.

  • Use SSH public key authentication.

  From Török Gábor

• use SSH public key authentication.

  From Hamza Yerlikaya

• Using public key (RSA) authentication is more secure and much more convenient. On a GNU/Linux system (and maybe others, I don't know) you typically would unlock your private key once per login session with a password and then use it.

  From Borbus