It is possible to configure your Pi to allow your computer to access it without providing a password each time you try to connect. To do this you need to generate an SSH key:
First, check whether there are already keys on the computer you are using to connect to the Raspberry Pi:
ls ~/.ssh
If you see files named id_rsa.pub or id_dsa.pub you have keys set up already, so you can skip the generating keys step (or delete these files with rm id* and make new keys).
To generate new SSH keys enter the following command (Choose a sensible hostname such as <YOURNANME>@<YOURDEVICE> where we have used eben@pi):
ssh-keygen -t rsa -C eben@pi
You can also use a more descriptive comment using quotes if you have spaces, e.g. ssh-keygen -t rsa -C "Raspberry Pi #123"
Upon entering this command, you'll be asked where to save the key. We suggest you save it in the default location (/home/pi/.ssh/id_rsa) by just hitting Enter.
You'll also be asked to enter a passphrase. This is extra security which will make the key unusable without your passphrase, so if someone else copied your key, they could not impersonate you to gain access. If you choose to use a passphrase, type it here and press Enter, then type it again when prompted. Leave the field empty for no passphrase.
Now you should see the files id_rsa and id_rsa.pub in your .ssh directory in your home folder:
ls ~/.ssh
authorized_keys id_rsa id_rsa.pub known_hosts
The id_rsa file is your private key. Keep this on your computer.
The id_rsa.pub file is your public key. This is what you put on machines you want to connect to. When the machine you try to connect to matches up your public and private key, it will allow you to connect.
Take a look at your public key to see what it looks like:
cat ~/.ssh/id_rsa.pub
It should be in the form:
ssh-rsa <REALLY LONG STRING OF RANDOM CHARACTERS> eben@pi
If your Pi does not have an .ssh directory you will need to set one up so that you can copy the key from your computer.
cd ~
install -d -m 700 ~/.ssh
To copy your public key to your Raspberry Pi, use the following command to append the public key to your authorized_keys file on the Pi, sending it over SSH:
cat ~/.ssh/id_rsa.pub | ssh <USERNAME>@<IP-ADDRESS> 'cat >> .ssh/authorized_keys'
Note that this time you will have to authenticate with your password.
Now try ssh <USER>@<IP-ADDRESS> and you should connect without a password prompt.
If you see a message "Agent admitted failure to sign using the key" then add your RSA or DSA identities to the authentication agent ssh-agent then execute the following command:
ssh-add
If this did not work, delete your keys with rm ~/.ssh/id* and follow the instructions again.
You can also send files over SSH using the scp command (secure copy). See the SCP guide for more information.