OpenSSH is being commonly used on Linux, it's it adapts different protocol and key pairs, so usually you don't need to worry about protocols and version things.

However, sometime, you may need to verify it, how?

Here is some tips:

My test environment:

$ssh -V
OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013

When generating ssh key pair:

     -t type
         Specifies the type of key to create. The possible values are:
         “rsa1” for protocol version 1 
         "rsa” or "dsa" for protocol version 2.

By looking at the key

     The user creates his/her key pair by running ssh-keygen.  This stores the private key in

      ~/.ssh/identity (protocol 1) 
      ~/.ssh/id_dsa (protocol 2 DSA) 
      ~/.ssh/id_ecdsa (protocol 2 ECDSA)
      ~/.ssh/id_rsa (protocol 2 RSA)

and
     stores the public key in

     ~/.ssh/identity.pub (protocol 1)
     ~/.ssh/id_dsa.pub (protocol 2 DSA)
     ~/.ssh/id_ecdsa.pub (protocol 2 ECDSA)
     ~/.ssh/id_rsa.pub (protocol 2 RSA)

SSH command option

ssh -1 ( protocol 1)
ssh -2 ( protocol 2)

The user should then copy  the public key to ~/.ssh/authorized_keys in his/her home directory on the remote machine.  The authorized_keys file has one key per line, though the lines can be very long.  After this, the user can log in without giving the password.

For detail setup, see setup SSH passphrase free access, for multiple ssh identities setup, see Config multiple SSH private keys on one client